information systems

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About the Authors Dr. Wm. Arthur Conklin is an associate professor and Director of the Center for Information Security Research and Education in the College of Technology at the University of Houston. He holds two terminal degrees, a Ph.D. in Business Administration (specializing in Information Security) from The University of Texas at San Antonio (UTSA) and the degree Electrical Engineer (specializing in Space Systems Engineering) from the Naval Postgraduate School in Monterey, CA. He holds CompTIA Security+, CISSP, CSSLP, CRISC, DFCP, GICSP, and CASP certifications. An ISSA Fellow, he is also a senior member of ASQ and a member of IEEE and ACM. His research interests include the use of systems theory to explore information security, specifically in cyber- physical systems. He has coauthored six security books and numerous academic articles associated with information security. He is active in the DHS-sponsored Industrial Control Systems Joint Working Group (ICSJWG) efforts associated with workforce development and cybersecurity aspects of industrial control systems. He has an extensive background in secure coding and is a former co-chair of the DHS/DoD Software Assurance Forum working group for workforce education, training, and development.

Dr. Gregory White has been involved in computer and network security since 1986. He spent 19 years on active duty with the U.S. Air Force and is currently in the Air Force Reserves assigned to the Pentagon. He obtained his Ph.D. in Computer Science from Texas A&M University in 1995. His dissertation topic was in the area of computer network intrusion detection, and he continues to conduct research in this area today. He is currently the Director for the Center for Infrastructure Assurance and Security and is an associate professor of computer science at The University of Texas at San Antonio. Dr. White has written and presented numerous articles and conference papers on security. He is also the coauthor for five textbooks on computer and network security and has written chapters for two other security books. Dr. White continues to be active in security research. His

current research initiatives include efforts in high-speed intrusion detection, community infrastructure protection, and visualization of community and organization security postures.

Dwayne Williams is Associate Director, Special Projects for the Center for Infrastructure Assurance and Security (CIAS) at the University of Texas at San Antonio and has more than 22 years of experience in information systems and network security. Mr. Williams’s experience includes six years of commissioned military service as a Communications- Computer Information Systems Officer in the U.S. Air Force, specializing in network security, corporate information protection, intrusion detection systems, incident response, and VPN technology. Prior to joining the CIAS, he served as Director of Consulting for SecureLogix Corporation, where he directed and provided security assessment and integration services to Fortune 100, government, public utility, oil and gas, financial, and technology clients. Mr. Williams graduated in 1993 from Baylor University with a Bachelor of Arts in Computer Science. Mr. Williams is a Certified Information Systems Security Professional (CISSP), CompTIA Advanced Security Practitioner (CASP), and coauthor of McGraw-Hill’s Voice and Data Security, CompTIA Security+ All-in-One Exam Guide, and CASP CompTIA Advanced Security Practitioner Certification Study Guide.

Roger L. Davis, CISSP, CISM, CISA, is an Account Manager for Microsoft. He has served as president of the Utah chapter of the Information Systems Security Association (ISSA) and various board positions for the Utah chapter of the Information Systems Audit and Control Association (ISACA). He is a retired Air Force lieutenant colonel with 35 years of military and information systems/security experience. Mr. Davis served on the faculty of Brigham Young University and the Air Force Institute of Technology. He coauthored McGraw-Hill’s CompTIA Security+ All-in-One Exam Guide and Voice and Data Security. He holds a Master’s degree in Computer Science from George Washington University, a Bachelor’s degree in Computer Science from Brigham

Young University, and performed post-graduate studies in electrical engineering and computer science at the University of Colorado.

Chuck Cothren, CISSP, is a Principal Solutions Specialist at Symantec Corporation applying a wide array of network security experience, including performing controlled penetration testing, incident response, and security management to assist a wide variety of clients in the protection of their critical data. He has also analyzed security methodologies for Voice over Internet Protocol (VoIP) systems and supervisory control and data acquisition (SCADA) systems. He is coauthor of the books Voice and Data Security, and CompTIA Security+ All-in-One Exam Guide.

About the Technical Editor Bobby E. Rogers is an Information Security Engineer working as a contractor for Department of Defense agencies, helping to secure, certify, and accredit their information systems. His duties include information system security engineering, risk management, and certification and accreditation efforts. He retired after 21 years in the United States Air Force, serving as a network security engineer and instructor, and has secured networks all over the world. Bobby has a Master’s degree in Information Assurance (IA), and is pursuing a doctoral degree in Cybersecurity from Capitol Technology University, Maryland. His many certifications include CRISC, CISSP-ISSEP, C|EH, and MCSE: Security as well as the CompTIA A+, Network+, Security+, and Mobility+ certifications.

Acknowledgments This book is dedicated to the many security professionals who daily

work to ensure the safety of our nation’s critical infrastructures. We want to recognize the thousands of dedicated individuals who strive to protect

our national assets but who seldom receive praise and often are only noticed when an incident occurs. To you, we say thank you for a job well

done!

We, the authors of Principles of Computer Security, Fourth Edition, have many individuals who we need to acknowledge—individuals without whom this effort would not have been successful. This edition would not have been possible without Tim Green, whose support and faith in the authors made this edition possible. He brought together an all-star production team that made this book more than just a new edition, but a complete learning system. The list needs to start with those folks at McGraw-Hill Education who

worked tirelessly with the project’s multiple authors and contributors and led us successfully through the minefield that is a book schedule and who took our rough chapters and drawings and turned them into a final, professional product we can be proud of. We thank all the good people from the Acquisitions team, Tim Green and Amy Stonebraker; from the Editorial Services team, Jody McKenzie and Howie Severson; from the Illustration and Production teams, James Kussow and Amarjeet Kumar and the composition team at Cenveo Publisher Services. We also thank the technical editor, Bobby Rogers; the copy editor, Bill McManus; the proofreader, Paul Tyler; and the indexer, Jack Lewis; for all their attention to detail that made this a finer work after they finished with it. We also need to acknowledge our current employers who, to our great

delight, have seen fit to pay us to work in a career field that we all find exciting and rewarding. There is never a dull moment in security, because it is constantly changing. We would like to thank Art Conklin for herding the cats on this one.

Finally, we would each like to individually thank those people who—on a personal basis—have provided the core support for us individually. Without these special people in our lives, none of us could have put this work together.

—The Author Team

To Susan, your love and support is what enables me to do all the things I do.

—Art Conklin, Ph.D. I would like to thank my wife, Charlan, for the tremendous support she has always given me. It doesn’t matter how many times I have sworn that I’ll never get involved with another book project only to return within months to yet another one; through it all, she has remained supportive. I would also like to publicly thank the United States Air Force, which

provided me numerous opportunities since 1986 to learn more about security than I ever knew existed. To whoever it was who decided to send me as a young captain—fresh from completing my master’s degree in artificial intelligence—to my first assignment in computer security: thank you, it has been a great adventure!

—Gregory B. White, Ph.D. Josie, thank you for all the love and support. Macon, John, this is for you.

—Chuck Cothren Geena, thanks for being my best friend and my greatest support. Anything I am is because of you. Love to my kids and grandkids!

—Roger L. Davis To my wife and best friend, Leah, for your love, energy, and support— thank you for always being there. Here’s to many more years together.

—Dwayne Williams

ABOUT THIS BOOK

Important Technology Skills Information technology (IT) offers many career paths, and information security is one of the fastest-growing tracks for IT professionals. This book provides coverage of the materials you need to begin your exploration of information security. In addition to covering all of the CompTIA Security+ exam objectives, additional material is included to help you build a solid introductory knowledge of information security.

Proven Learning Method Keeps You on Track Designed for classroom use and written by instructors for use in their own classes, Principles of Computer Security is structured to give you comprehensive knowledge of information security. The textbook’s active learning methodology guides you beyond mere recall and— through thought-provoking activities, labs, and sidebars—helps you develop critical-thinking, diagnostic, and communication skills.

Effective Learning Tools This feature-rich textbook is designed to make learning easy and enjoyable and to help you develop the skills and critical-thinking abilities that will enable you to adapt to different job situations and to troubleshoot problems. Written by instructors with decades of combined information security experience, this book conveys even the most complex issues in an accessible, easy-to understand format.

Each chapter includes

Learning Objectives that set measurable goals for chapter-by- chapter progress

Illustrations that give you a clear picture of the concepts and technologies

Try This!, Cross Check, and Tech Tip sidebars that encourage you to practice and apply concepts in real-world settings

Notes, Tips, and Warnings that guide you, and Exam Tips that give you advice or provide information specifically related to preparing for the exam

Chapter Summaries and Key Terms Lists that provide you with an easy way to review important concepts and vocabulary

Challenging End-of-Chapter Tests that include vocabulary- building exercises, multiple-choice questions, essay questions, and on-the-job lab projects

CompTIA APPROVED QUALITY CONTENT

It Pays to Get Certified In a digital world, digital literacy is an essential survival skill. Certification demonstrates that you have the knowledge and skill to solve technical or business problems in virtually any business environment. CompTIA certifications are highly valued credentials that qualify you for jobs, increased compensation, and promotion.

CompTIA Security+ Certification Helps Your

Career

Security is one of the highest demand job categories, growing in importance as the frequency and severity of security threats continues to be a major concern for organizations around the world.

Jobs for security administrators are expected to increase by 18% —the skill set required for these types of jobs maps to the CompTIA Security+ certification.

Network Security Administrators can earn as much as $106,000 per year.

CompTIA Security+ is the first step in starting your career as a Network Security Administrator or Systems Security Administrator.

More than 250,000 individuals worldwide are CompTIA Security+ certified.

CompTIA Security+ is regularly used in organizations such as Hitachi Systems, Fuji Xerox, HP, Dell, and a variety of major U.S. government contractors.

Approved by the U.S. Department of Defense (DoD) as one of the required certification options in the DoD 8570.01-M directive, for Information Assurance Technical Level II and Management Level I job roles.

Steps to Getting Certified and Staying Certified 1. Review the exam objectives. Review the certification objectives to

make sure you know what is covered in the exam: http://certification.comptia.org/examobjectives.aspx

2. Practice for the exam. After you have studied for the certification exam, review and answer sample questions to get an idea of what type of questions might be on the exam: http://certification.comptia.org/samplequestions.aspx

3. Purchase an exam voucher. You can purchase exam vouchers on the CompTIA Marketplace, www.comptiastore.com.

4. Take the test! Go to the Pearson VUE website, www.pearsonvue.com/comptia/, and schedule a time to take your exam.

5. Stay certified! Effective January 1, 2011, new CompTIA Security+ certifications are valid for three years from the date of certification. There are a number of ways the certification can be renewed. For more information go to http://certification.comptia.org/ce.

For More Information Visit CompTIA online Go to http://certification.comptia.org/home.aspx to learn more about getting CompTIA certified.

Contact CompTIA Please call 866-835-8020 and choose Option 2, or e-mail [email protected].

Connect with CompTIA Find CompTIA on Facebook, LinkedIn, Twitter, and YouTube.

Content Seal of Quality This courseware bears the seal of CompTIA Approved Quality Content. This seal signifies this content covers 100 percent of the exam objectives and implements important instructional design principles. CompTIA recommends multiple learning tools to help increase coverage of the learning objectives.

CAQC Disclaimer The logo of the CompTIA Approved Quality Content (CAQC) program and the status of this or other training material as “Approved” under the CompTIA Approved Quality Content program signifies that, in CompTIA’s opinion, such training material covers the content of CompTIA’s related certification exam. The contents of this training material were created for the CompTIA

Security+ exam covering CompTIA certification objectives that were current as of the date of publication. CompTIA has not reviewed or approved the accuracy of the contents of

this training material and specifically disclaims any warranties of merchantability or fitness for a particular purpose. CompTIA makes no guarantee concerning the success of persons using any such “Approved” or other training material in order to prepare for any CompTIA certification exam.

CONTENTS AT A GLANCE

Chapter 1 Introduction and Security Trends

Chapter 2 General Security Concepts

Chapter 3 Operational and Organizational Security

Chapter 4 The Role of People in Security

Chapter 5 Cryptography

Chapter 6 Public Key Infrastructure

Chapter 7 PKI Standards and Protocols

Chapter 8 Physical Security

Chapter 9 Network Fundamentals

Chapter 10 Infrastructure Security

Chapter 11 Authentication and Remote Access

Chapter 12 Wireless Security and Mobile Devices

Chapter 13 Intrusion Detection Systems and Network Security

Chapter 14 System Hardening and Baselines

Chapter 15 Types of Attacks and Malicious Software

Chapter 16 E-Mail and Instant Messaging

Chapter 17 Web Components

Chapter 18 Secure Software Development

Chapter 19 Business Continuity and Disaster Recovery, and Organizational Policies

Chapter 20 Risk Management

Chapter 21 Change Management

Chapter 22 Incident Response

Chapter 23 Computer Forensics

Chapter 24 Legal Issues and Ethics

Chapter 25 Privacy

Appendix A CompTIA Security+ Exam Objectives: SY0-401

Appendix B About the Download

Glossary

Index

CONTENTS

Foreword Preface Introduction Instructor Web Site

Chapter 1 Introduction and Security Trends The Computer Security Problem

Definition of Computer Security Historical Security Incidents The Current Threat Environment Threats to Security Security Trends

Targets and Attacks Specific Target Opportunistic Target Minimizing Possible Avenues of Attack

Approaches to Computer Security Ethics Additional References Chapter 1 Review

Chapter 2 General Security Concepts Basic Security Terminology

Security Basics

Security Tenets Security Approaches Security Principles Access Control Authentication Mechanisms Authentication and Access Control Policies

Security Models Confidentiality Models Integrity Models

Chapter 2 Review

Chapter 3 Operational and Organizational Security Policies, Procedures, Standards, and Guidelines

Security Policies Change Management Policy Data Policies Human Resources Policies Due Care and Due Diligence Due Process Incident Response Policies and Procedures

Security Awareness and Training Security Policy Training and Procedures Role-Based Training Compliance with Laws, Best Practices, and Standards User Habits New Threats and Security Trends/Alerts Training Metrics and Compliance

Interoperability Agreements Service Level Agreements Business Partnership Agreement

Memorandum of Understanding Interconnection Security Agreement

The Security Perimeter Physical Security

Physical Access Controls Physical Barriers

Environmental Issues Fire Suppression

Wireless Electromagnetic Eavesdropping

Modern Eavesdropping Chapter 3 Review

Chapter 4 The Role of People in Security People—A Security Problem

Social Engineering Poor Security Practices

People as a Security Tool Security Awareness Security Policy Training and Procedures

Chapter 4 Review

Chapter 5 Cryptography Cryptography in Practice

Fundamental Methods Comparative Strengths and Performance of Algorithms

Historical Perspectives Substitution Ciphers One-Time Pads

Algorithms Key Management Random Numbers

Hashing Functions SHA RIPEMD Message Digest Hashing Summary

Symmetric Encryption DES 3DES AES CAST RC Blowfish Twofish IDEA Block vs. Stream Symmetric Encryption Summary

Asymmetric Encryption Diffie-Hellman RSA ElGamal ECC Asymmetric Encryption Summary Symmetric vs. Asymmetric

Quantum Cryptography Steganography Cryptography Algorithm Use

Confidentiality Integrity

Authentication Nonrepudiation Cipher Suites Key Exchange Key Escrow Session Keys Ephemeral Keys Key Stretching Secrecy Principles Transport Encryption Digital Signatures Digital Rights Management Cryptographic Applications Use of Proven Technologies

Chapter 5 Review

Chapter 6 Public Key Infrastructure The Basics of Public Key Infrastructures Certificate Authorities Registration Authorities

Local Registration Authorities Digital Certificates

Certificate Extensions Certificate Attributes

Certificate Lifecycles Registration and Generation CSR Renewal Suspension Revocation

Key Destruction Certificate Repositories Trust and Certificate Verification Centralized and Decentralized Infrastructures

Hardware Security Modules Private Key Protection Key Recovery Key Escrow

Public Certificate Authorities In-House Certificate Authorities

Choosing Between a Public CA and an In-House CA Outsourced Certificate Authorities Tying Different PKIs Together Trust Models

Certificate-Based Threats Stolen Certificates

Chapter 6 Review

Chapter 7 PKI Standards and Protocols PKIX and PKCS

PKIX Standards PKCS Why You Need to Know the PKIX and PKCS Standards

X.509 SSL/TLS Cipher Suites ISAKMP CMP XKMS S/MIME

IETF S/MIME History IETF S/MIME v3 Specifications

PGP How PGP Works

HTTPS IPsec CEP Other Standards

FIPS Common Criteria WTLS ISO/IEC 27002 (Formerly ISO 17799) SAML

Chapter 7 Review

Chapter 8 Physical Security The Security Problem Physical Security Safeguards

Walls and Guards Physical Access Controls and Monitoring Convergence Policies and Procedures Environmental Controls

Fire Suppression Water-Based Fire Suppression Systems Halon-Based Fire Suppression Systems Clean-Agent Fire Suppression Systems Handheld Fire Extinguishers Fire Detection Devices

Power Protection

UPS Backup Power and Cable Shielding Electromagnetic Interference

Electronic Access Control Systems Access Tokens

Chapter 8 Review

Chapter 9 Network Fundamentals Network Architectures Network Topology Network Protocols

Protocols Packets

Internet Protocol IP Packets TCP vs. UDP ICMP

IPv4 vs. IPv6 Packet Delivery

Ethernet Local Packet Delivery Remote Packet Delivery IP Addresses and Subnetting Network Address Translation

Security Zones DMZ Internet Intranet Extranet Flat Networks

Enclaves VLANs Zones and Conduits

Tunneling Storage Area Networks

iSCSI Fibre Channel FCoE

Chapter 9 Review

Chapter 10 Infrastructure Security Devices

Workstations Servers Virtualization Mobile Devices Device Security, Common Concerns Network Attached Storage Removable Storage

Networking Network Interface Cards Hubs Bridges Switches Routers Firewalls How Do Firewalls Work? Next-Generation Firewalls Web Application Firewalls vs. Network Firewalls Concentrators

Wireless Devices Modems Telephony VPN Concentrator

Security Devices Intrusion Detection Systems Network Access Control Network Monitoring/Diagnostic Load Balancers Proxies Web Security Gateways Internet Content Filters Data Loss Prevention Unified Threat Management

Media Coaxial Cable UTP/STP Fiber Unguided Media

Removable Media Magnetic Media Optical Media Electronic Media

Security Concerns for Transmission Media Physical Security Concerns Cloud Computing

Private Public Hybrid Community Software as a Service

Platform as a Service Infrastructure as a Service

Chapter 10 Review

Chapter 11 Authentication and Remote Access User, Group, and Role Management

User Group Role

Password Policies Domain Password Policy

Single Sign-On Time of Day Restrictions Tokens Account and Password Expiration

Security Controls and Permissions Access Control Lists Mandatory Access Control (MAC) Discretionary Access Control (DAC) Role-Based Access Control (RBAC) Rule-Based Access Control Attribute Based Access Control (ABAC) Account Expiration

Preventing Data Loss or Theft The Remote Access Process

Identification Authentication Authorization Access Control

Remote Access Methods

IEEE 802.1X RADIUS TACACS+ Authentication Protocols FTP/FTPS/SFTP VPNs IPsec Vulnerabilities of Remote Access Methods

Connection Summary Chapter 11 Review

Chapter 12 Wireless Security and Mobile Devices Introduction to Wireless Networking Mobile Phones

Wireless Application Protocol 3G Mobile Networks 4G Mobile Networks

Bluetooth Bluetooth Attacks

Near Field Communication IEEE 802.11 Series

802.11: Individual Standards Attacking 802.11 Current Security Methods

Wireless Systems Configuration Antenna Types Antenna Placement Power Level Controls Site Surveys Captive Portals

Securing Public Wi-Fi Mobile Devices

Mobile Device Security BYOD Concerns Location Services Mobile Application Security

Chapter 12 Review

Chapter 13 Intrusion Detection Systems and Network Security History of Intrusion Detection Systems IDS Overview

IDS Models Signatures False Positives and False Negatives

Network-Based IDSs Advantages of a NIDS Disadvantages of a NIDS Active vs. Passive NIDSs NIDS Tools

Host-Based IDSs Advantages of HIDSs Disadvantages of HIDSs Active vs. Passive HIDSs Resurgence and Advancement of HIDSs

Intrusion Prevention Systems Honeypots and Honeynets Tools

Protocol Analyzer Switched Port Analyzer Port Scanner

Passive vs. Active Tools Banner Grabbing

Chapter 13 Review

Chapter 14 System Hardening and Baselines Overview of Baselines Operating System and Network Operating System Hardening

OS Security Host Security

Machine Hardening Operating System Security and Settings OS Hardening Hardening Microsoft Operating Systems Hardening UNIX- or Linux-Based Operating Systems Updates (a.k.a. Hotfixes, Service Packs, and Patches) Antimalware White Listing vs. Black Listing Applications Trusted OS Host-based Firewalls Hardware Security Host Software Baselining

Host-Based Security Controls Hardware-Based Encryption Devices Data Encryption Data Security Handling Big Data Cloud Storage Storage Area Network Permissions/ACL

Network Hardening

Software Updates Device Configuration Securing Management Interfaces VLAN Management IPv4 vs. IPv6

Application Hardening Application Configuration Baseline Application Patches Patch Management Host Software Baselining

Group Policies Security Templates Alternative Environments

SCADA Embedded Systems Phones and Mobile Devices Mainframe Game Consoles In-Vehicle Computing Systems Alternative Environment Methods Network Segmentation Security Layers Application Firewalls Manual Updates Firmware Version Control Wrappers Control Redundancy and Diversity

Chapter 14 Review

Chapter 15 Types of Attacks and Malicious Software

Avenues of Attack Minimizing Possible Avenues of Attack

Malicious Code Viruses Worms Polymorphic Malware Trojan Horses Rootkits Logic Bombs Spyware Adware Botnets Backdoors and Trapdoors Ransomware Malware Defenses

Attacking Computer Systems and Networks Denial-of-Service Attacks Social Engineering Null Sessions Sniffing Spoofing TCP/IP Hijacking Man-in-the-Middle Attacks Replay Attacks Transitive Access Spam Spim Phishing Spear Phishing Vishing Pharming

Scanning Attacks Attacks on Encryption Address System Attacks Cache Poisoning Password Guessing Pass-the-Hash Attacks Software Exploitation Client-Side Attacks

Advanced Persistent Threat Remote Access Trojans

Tools Metasploit BackTrack/Kali Social-Engineering Toolkit Cobalt Strike Core Impact Burp Suite

Auditing Perform Routine Audits

Chapter 15 Review

Chapter 16 E-Mail and Instant Messaging How E-Mail Works

E-Mail Structure MIME

Security of E-Mail Malicious Code Hoax E-Mails Unsolicited Commercial E-Mail (Spam) Sender ID Framework

DomainKeys Identified Mail Mail Encryption

S/MIME PGP

Instant Messaging Modern Instant Messaging Systems

Chapter 16 Review

Chapter 17 Web Components Current Web Components and Concerns Web Protocols

Encryption (SSL and TLS) The Web (HTTP and HTTPS) HTTPS Everywhere HTTP Strict Transport Security Directory Services (DAP and LDAP) File Transfer (FTP and SFTP) Vulnerabilities

Code-Based Vulnerabilities Buffer Overflows Java JavaScript ActiveX Securing the Browser CGI Server-Side Scripts Cookies Browser Plug-ins Malicious Add-ons Signed Applets

Application-Based Weaknesses Session Hijacking Client-Side Attacks Web 2.0 and Security

Chapter 17 Review

Chapter 18 Secure Software Development The Software Engineering Process

Process Models Secure Development Lifecycle

Secure Coding Concepts Error and Exception Handling Input and Output Validation Fuzzing Bug Tracking

Application Attacks Cross-Site Scripting Injections Directory Traversal/Command Injection Buffer Overflow Integer Overflow Cross-Site Request Forgery Zero-Day Attachments Locally Shared Objects Client-Side Attacks Arbitrary/Remote Code Execution Open Vulnerability and Assessment Language

Application Hardening Application Configuration Baseline

Application Patch Management NoSQL Databases vs. SQL Databases Server-Side vs. Client-Side Validation

Chapter 18 Review

Chapter 19 Business Continuity and Disaster Recovery, and Organizational Policies

Business Continuity Business Continuity Plans Business Impact Analysis Identification of Critical Systems and Components Removing Single Points of Failure Risk Assessment Succession Planning Continuity of Operations

Disaster Recovery Disaster Recovery Plans/Process Categories of Business Functions IT Contingency Planning Test, Exercise, and Rehearse Recovery Time Objective and Recovery Point Objective Backups Alternative Sites Utilities Secure Recovery Cloud Computing High Availability and Fault Tolerance Failure and Recovery Timing

Chapter 19 Review

Chapter 20 Risk Management An Overview of Risk Management

Example of Risk Management at the International Banking Level Risk Management Vocabulary

What Is Risk Management? Risk Management Culture

Business Risks Examples of Business Risks Examples of Technology Risks

Risk Mitigation Strategies Change Management Incident Management User Rights and Permissions Reviews Data Loss or Theft

Risk Management Models General Risk Management Model Software Engineering Institute Model NIST Risk Models Model Application

Qualitatively Assessing Risk Quantitatively Assessing Risk

Adding Objectivity to a Qualitative Assessment Risk Calculation

Qualitative vs. Quantitative Risk Assessment Tools

Cost-Effectiveness Modeling Risk Management Best Practices

System Vulnerabilities Threat Vectors Probability/Threat Likelihood

Risk-Avoidance, Transference, Acceptance, Mitigation, Deterrence Risks Associated with Cloud Computing and Virtualization

Chapter 20 Review

Chapter 21 Change Management Why Change Management? The Key Concept: Separation of Duties Elements of Change Management Implementing Change Management

Back-out Plan The Purpose of a Change Control Board

Code Integrity The Capability Maturity Model Integration Chapter 21 Review

Chapter 22 Incident Response Foundations of Incident Response

Incident Management Anatomy of an Attack Goals of Incident Response

Incident Response Process Preparation Security Measure Implementation Incident Identification/Detection Initial Response Incident Isolation Strategy Formulation Investigation Recovery/Reconstitution Procedures

Reporting Follow-up/Lessons Learned

Standards and Best Practices State of Compromise NIST Department of Justice Indicators of Compromise Cyber Kill Chain Making Security Measurable

Chapter 22 Review

Chapter 23 Computer Forensics Evidence

Types of Evidence Standards for Evidence Three Rules Regarding Evidence

Forensic Process Acquiring Evidence Identifying Evidence Protecting Evidence Transporting Evidence Storing Evidence Conducting the Investigation

Analysis Chain of Custody Message Digest and Hash Host Forensics

File Systems  Windows Metadata Linux Metadata

Device Forensics Network Forensics E-Discovery

Reference Model Big Data Cloud

Chapter 23 Review

Chapter 24 Legal Issues and Ethics Cybercrime

Common Internet Crime Schemes Sources of Laws Computer Trespass Significant U.S. Laws Payment Card Industry Data Security Standard (PCI DSS) Import/Export Encryption Restrictions Non-U.S. Laws Digital Signature Laws Digital Rights Management

Ethics Chapter 24 Review

Chapter 25 Privacy Personally Identifiable Information (PII)

Sensitive PII Notice, Choice, and Consent

U.S. Privacy Laws Privacy Act of 1974 Freedom of Information Act (FOIA)

Family Education Records and Privacy Act (FERPA) U.S. Computer Fraud and Abuse Act (CFAA) U.S. Children’s Online Privacy Protection Act (COPPA) Video Privacy Protection Act (VPPA) Health Insurance Portability & Accountability Act (HIPAA) Gramm-Leach-Bliley Act (GLBA) California Senate Bill 1386 (SB 1386) U.S. Banking Rules and Regulations Payment Card Industry Data Security Standard (PCI DSS) Fair Credit Reporting Act (FCRA) Fair and Accurate Credit Transactions Act (FACTA)

Non-Federal Privacy Concerns in the United States International Privacy Laws

OECD Fair Information Practices European Laws Canadian Laws Asian Laws

Privacy-Enhancing Technologies Privacy Policies

Privacy Impact Assessment Web Privacy Issues

Cookies Privacy in Practice

User Actions Data Breaches

Chapter 25 Review

Appendix A CompTIA Security+ Exam Objectives: SY0-401

Appendix B

About the Download System Requirements Downloading Total Tester Premium Practice Exam Software Total Tester Premium Practice Exam Software

Installing and Running Total Tester Technical Support

Total Seminars Technical Support McGraw-Hill Education Content Support

Glossary

Index

FOREWORD

Selecting a book is tricky for me. If it is for personal reading, will I like reading it? If it is for my professional development, will it meet the need? If it is for my students, will it be clear and concise? This new edition of Principles of Computer Security passes all three tests with flying colors. I enjoyed reading it. If I needed to pass the CompTIA Security+ or other practitioner examination, it would prepare me. And finally, based on personal experience, students will like this book and find it to be valuable reading and study material. It even has practice exams for certification for my convenience. For more than 40 years I have worked in some variety of computer

security. When people ask me what defines my job, I respond with “I don’t know until I read the morning newspaper because the security environment changes rapidly.” If you want to get into the computer security industry, reading and understanding this book is a great introduction. Now in its fourth edition, the 25 chapters of Principles of Computer Security focus on a broad spectrum of important topics to prepare the reader to be a certified computer security practitioner. The real deal maker for me is the further endorsement of the contents: the book is based on CompTIA Approved Quality Content (CAQC) and serves as both an exam preparation guide and a useful reference. Dr. Conklin and his team of coauthors ease the reader into the meat of

the topic by reviewing both security trends and concepts. They then address security from two different perspectives. First they focus on the organization’s need for security, and then focus on the important role of people. These two perspectives are intertwined; it is essential for a security practitioner to understand the security environment and how the people make it work. Every practitioner needs to understand the underlying technology and

tools of computer security. Some individuals have an idea about security topics but do not have the essential knowledge needed to address them in depth. The authors have provided nine masterful chapters introducing these key concepts. For example, in a single chapter they provide the basis for the reader to deal with security of networks. This chapter supports everything the reader needs to know to address standards and protocols, infrastructure security, remote access and authentication, as well as wireless. The authors integrate these concepts to support public key infrastructure (PKI) and intrusion detection systems for network security without forgetting the importance of physical security in protecting the information system as well as infrastructure. One of the most debated topics in security is the importance of

cryptography. Some would assert that almost all digital security can be accomplished with cryptography, that security and cryptography are inseparable, with cryptography being the cornerstone of securing data in both transmission and storage. However, if computer security were as easy as “encrypt everything,” this would be a very short book. While cryptography is very important and a very complex security measure, it is not a panacea—but it does provide for lively discussions. The authors bring all these components together with a comprehensive chapter on intrusion detection and prevention. Once the reader has mastered the basics, the authors address e-mail,

malicious software, instant messaging, and web components in such a way that the reader can apply his or her knowledge of networks and security fundamentals. The reader will then be provided with an overview of secure software development. In 2015, both the U.S. Department of Homeland Security and CSO magazine concluded that poorly developed software is one of the biggest cyber threats—perhaps 90 percent of the threats come through poor software design. In the final analysis, security is really all about risk management. What

is your organization’s appetite for risk and how is that risk managed? The chapters covering risk management lead the reader through these less technical issues to gain an understanding how these impact the

organization. Baselines and change management are essential to understanding what assets are being secured and how they are being changed. A reader who learns these skills well will be able to work in incident response, disaster recovery, and business continuity. Understanding these processes and how they work with technical issues expands career opportunities. The authors conclude their review of the principles of computer security

with an examination of privacy, legal issues, and ethics. Although these topics appear at the end of the book, they are crucial issues in the modern world. Remember, as a computer security practitioner, you will have legal access to more data and information than any else in the organization. Although not the last chapter in the book, I have decided to comment on

forensics last. The authors have done a wonderful job of addressing this complex topic. But why mention it last? Because many times forensics is what one does after computer security fails. It makes a good epitaph for a wonderful book. Tonight it is 15 degrees and snowing outside while I sit in my study—

warm, dry, and comfortable; my home is my castle. Not bad for mid- winter in Idaho; however, I should not forget that one reason I am comfortable is because certified computer security practitioners are protecting my information and privacy as well as the critical infrastructure that supports it.

For Instructors I have taught from prior editions of this book and have used its companion laboratory manual for several years. Both Principles of Computer Security, Fourth Edition and Principles of Computer Security Lab Manual, Fourth Edition have instructor materials on a companion Web site available to adopting instructors. Instructor manuals, including the answers to the end- of-chapter questions, PowerPoint slides, and the test bank of questions for use as quizzes or exams, make preparation a snap.

Corey D. Schou, PhD Series Editor

University Professor of Informatics Professor of Computer Science

Director of the National Information Assurance Training and Education Center

Idaho State University

PREFACE

Information and computer security has moved from the confines of academia to mainstream America in the 21st century. Data breaches, information disclosures, and high-profile hacks involving the theft of information and intellectual property seem to be a regular staple of the news. It has become increasingly obvious to everybody that something needs to be done to secure not only our nation’s critical infrastructure but also the businesses we deal with on a daily basis. The question is, “Where do we begin?” What can the average information technology professional do to secure the systems that he or she is hired to maintain? One immediate answer is education and training. If we want to secure our computer systems and networks, we need to know how to do this and what security entails. Our way of life, from commerce to messaging to business

communications and even social media, depends on the proper functioning of our worldwide infrastructure. A common thread throughout all of these, however, is technology—especially technology related to computers and communication. Thus, an individual, organization, or nation who wanted to cause damage to this nation could attack it not just with traditional weapons but with computers through the Internet. Complacency is not an option in today’s hostile network environment. The protection of our networks and systems is not the sole domain of the information security professional, but rather the responsibility of all who are involved in the design, development, deployment, and operation of the systems that are nearly ubiquitous in our daily lives. With virtually every system we depend upon daily at risk, the attack surface and corresponding risk profile is extremely large. Information security has matured from a series of technical issues to a comprehensive risk management problem, and this book provides the foundational material to engage in the field in a

professional manner. So, where do you, the IT professional seeking more knowledge on

security, start your studies? This book offers a comprehensive review of the underlying foundations and technologies associated with securing our systems and networks. The IT world is overflowing with certifications that can be obtained by those attempting to learn more about their chosen profession. The information security sector is no different, and the CompTIA Security+ exam offers a basic level of certification for security. In the pages of this book you will find not only material that can help you prepare for taking the CompTIA Security+ exam but also the basic information that you will need in order to understand the issues involved in securing your computer systems and networks today. In no way is this book the final source for learning all about protecting your organization’s systems, but it serves as a point from which to launch your security studies and career. One thing is certainly true about this field of study—it never gets

boring. It constantly changes as technology itself advances. Something else you will find as you progress in your security studies is that no matter how much technology advances and no matter how many new security devices are developed, at its most basic level, the human is still the weak link in the security chain. If you are looking for an exciting area to delve into, then you have certainly chosen wisely. Security offers a challenging blend of technology and people issues. And securing the systems of tomorrow will require everyone to work together, not just security, but developers, operators, and users alike. We, the authors of this book, wish you luck as you embark on an exciting and challenging career path.

Wm. Arthur Conklin, Ph.D. Gregory B. White, Ph.D.

INTRODUCTION

Computer security is becoming increasingly important today as the number of security incidents steadily climbs. Many corporations are now spending significant portions of their budgets on security hardware, software, services, and personnel. They are spending this money not because it increases sales or enhances the product they provide, but because of the possible consequences should they not take protective actions. Security has become a comprehensive risk management exercise in firms that take the risks seriously.

Why Focus on Security? Security is not something that we want to have to pay for; it would be nice if we didn’t have to worry about protecting our data from disclosure, modification, or destruction from unauthorized individuals, but that is not the environment we find ourselves in today. Instead, we have seen the cost of recovering from security incidents steadily rise along with the rise in the number of incidents themselves. Since hackers have learned how to monetize hacks, the playing field has become significantly more dangerous. There are now incentives for a professional class of hacker with the intent of reaping benefits both long and short term. With the advent of advanced persistent threats, the rise of nation-state hacking, and the increase in criminal activity from botnets to ransomware, the IT playing field is now viewed as a contested environment, one where hacking can result in gains. Law enforcement is too overwhelmed and under-resourced to make a dent in the problem, and the result is a need for trained security practitioners in all business segments—and a further need for security-aware IT personnel in regular IT positions. Security has become a mainstream topic.

A Growing Need for Security Specialists To protect our computer systems and networks, we will need a significant number of new security professionals trained in the many aspects of computer and network security. This is not an easy task, as the systems connected to the Internet become increasingly complex, with software whose lines of code number in the millions. Understanding why this is such a difficult problem to solve is not hard if you consider how many errors might be present in a piece of software that is several million lines long. When you add the additional factor of how fast software is being developed—from necessity as the market is constantly moving— understanding how errors occur is easy. Not every “bug” in the software will result in a security hole, but it

doesn’t take many to affect the Internet community drastically. We can’t just blame the vendors for this situation, because they are reacting to the demands of government and industry. Most vendors are fairly adept at developing patches for flaws found in their software, and patches are constantly issued to protect systems from bugs that may introduce security problems. This introduces a whole new problem for managers and administrators—patch management. How important this has become is easily illustrated by how many of the most recent security events have occurred as a result of a security bug for which a patch was available months prior to the security incident; members of the community had not correctly installed the patch, however, thus making the incident possible. One of the reasons this happens is that many of the individuals responsible for installing the patches are not trained to understand the security implications surrounding the hole or the ramifications of not installing the patch. Many of these individuals simply lack the necessary training. Because of the need for an increasing number of security professionals

who are trained to some minimum level of understanding, certifications such as the CompTIA Security+ have been developed. Prospective employers want to know that the individual they are considering hiring knows what to do in terms of security. The prospective employee, in turn, wants to have a way to demonstrate his or her level of understanding,

which can enhance the candidate’s chances of being hired. The community as a whole simply wants more trained security professionals.

Preparing Yourself for the CompTIA Security+ Exam Principles of Computer Security, Fourth Edition is designed to help prepare you to take the CompTIA Security+ certification exam. When you pass it, you will demonstrate you have that basic understanding of security that employers are looking for. Passing this certification exam will not be an easy task, for you will need to learn many things to acquire that basic understanding of computer and network security.

How This Book Is Organized The book is divided into chapters to correspond with the objectives of the exam itself. Some of the chapters are more technical than others— reflecting the nature of the security environment where you will be forced to deal with not only technical details but also other issues such as security policies and procedures as well as training and education. Although many individuals involved in computer and network security have advanced degrees in math, computer science, information systems, or computer or electrical engineering, you do not need this technical background to address security effectively in your organization. You do not need to develop your own cryptographic algorithm, for example; you simply need to be able to understand how cryptography is used, along with its strengths and weaknesses. As you progress in your studies, you will learn that many security problems are caused by the human element. The best technology in the world still ends up being placed in an environment where humans have the opportunity to foul things up—and all too often do.

Onward and Upward

At this point, we hope that you are now excited about the topic of security, even if you weren’t in the first place. We wish you luck in your endeavors and welcome you to the exciting field of computer and network security.

INSTRUCTOR WEB SITE

For instructor resources, visit www.mhprofessional.com/PrinciplesSecurity4e. Adopting teachers can access the support materials identified below. Contact your McGraw-Hill Education sales representative for details on how to access the materials.

Instructor Materials The Principles of Computer Security companion Web site (www.mhprofessional.com/PrinciplesSecurity4e) provides many resources for instructors:

Answer keys to the end-of-chapter activities in the textbook

Answer keys to the lab manual activities (lab manual available separately)

Engaging PowerPoint slides on the lecture topics (including full-color artwork from the book)

An Instructor Manual

Access to test bank files and software that allows you to generate a wide array of paper- or network-based tests, and that features automatic grading

Hundreds of practice questions and a wide variety of question types and difficulty levels, enabling you to customize each test to maximize student progress

Blackboard cartridges and other formats may also be available upon request; contact your sales representative

chapter 1 Introduction and Security Trends

Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is

W

either a daring adventure or nothing.

—HELEN KELLER

In this chapter, you will learn how to

Define computer security

Discuss common threats and recent computer crimes that have been committed

List and discuss recent trends in computer security

Describe common avenues of attacks

Describe approaches to computer security

Discuss the relevant ethical issues associated with computer security

hy should we be concerned about computer and network security? All you have to do is turn on the television or read the newspaper to find out about a variety of security problems that affect our nation

and the world today. The danger to computers and networks may seem to pale in comparison to the threat of terrorist strikes, but in fact the average citizen is much more likely to be the target of an attack on their own personal computer, or a computer they use at their place of work, than they are to be the direct victim of a terrorist attack. This chapter will introduce you to a number of issues involved in securing your computers and networks from a variety of threats that may utilize any of a number of different attacks.

The Computer Security Problem Fifty years ago companies did not conduct business across the Internet. Online banking and shopping were only dreams in science fiction stories. Today, however, millions of people perform online transactions every day. Companies rely on the Internet to operate and conduct business. Vast amounts of money are transferred via networks, in the form of either bank transactions or simple credit card purchases. Wherever there are vast

amounts of money, there are those who will try to take advantage of the environment to conduct fraud or theft. There are many different ways to attack computers and networks to take advantage of what has made shopping, banking, investment, and leisure pursuits a simple matter of “dragging and clicking” (or tapping) for many people. Identity theft is so common today that most everyone knows somebody who’s been a victim of such a crime, if they haven’t been a victim themselves. This is just one type of criminal activity that can be conducted using the Internet. There are many others and all are on the rise.

Definition of Computer Security Computer security is not a simple concept to define, and has numerous complexities associated with it. If one is referring to a computer, then it can be considered secure when the computer does what it is supposed to do and only what it is supposed to do. But as was noted earlier, the security emphasis has shifted from the computer to the information being processed. Information security is defined by the information being protected from unauthorized access or alteration and yet is available to authorized individuals when required. When one begins considering the aspects of information, it is important to realize that information is stored, processed, and transferred between machines, and all of these different states require appropriate protection schemes. Information assurance is a term used to describe not just the protection of information, but a means of knowing the level of protection that has been accomplished.

Tech Tip

Historical Computer Security Computer security is an ever-changing issue. Fifty years ago, computer security was mainly concerned with the physical devices that made up the computer. At the time, computers were the high-value items that organizations could not afford to lose. Today, computer equipment is inexpensive compared to the value of the data processed by the computer. Now the high-value

item is not the machine, but the information that it stores and processes. This has fundamentally changed the focus of computer security from what it was in the early years. Today the data stored and processed by computers is almost always more valuable than the hardware.

Computer security and information security both refer to a state where the hardware and software perform only desired actions and the information is protected from unauthorized access or alteration and is available to authorized users when required.

Historical Security Incidents By examining some of the computer-related crimes that have been committed over the last 30 or so years, we can better understand the threats and security issues that surround our computer systems and networks. Electronic crime can take a number of different forms, but the ones we will examine here fall into two basic categories: crimes in which the computer was the target, and incidents in which a computer was used to perpetrate the act (for example, there are many different ways to conduct bank fraud, one of which uses computers to access the records that banks process and maintain). We will start our tour of computer crimes with the 1988 Internet worm

(Morris worm), one of the first real Internet crime cases. Prior to 1988, criminal activity was chiefly centered on unauthorized access to computer systems and networks owned by the telephone company and companies that provided dial-up access for authorized users. Virus activity also existed prior to 1988, having started in the early 1980s.

The Morris Worm (November 1988) Robert Morris, then a graduate student at Cornell University, released what has become known as the Internet worm (or the Morris worm). The worm infected roughly 10 percent of the machines then connected to the Internet

(which amounted to approximately 6000 infected machines). The worm carried no malicious payload, the program being obviously a “work in progress,” but it did wreak havoc because it continually re-infected computer systems until they could no longer run any programs.

Citibank and Vladimir Levin (June–October 1994) Starting about June of 1994 and continuing until at least October of the same year, a number of bank transfers were made by Vladimir Levin of St. Petersburg, Russia. By the time he and his accomplices were caught, they had transferred an estimated $10 million. Eventually all but about $400,000 was recovered. Levin reportedly accomplished the break-ins by dialing into Citibank’s cash management system. This system allowed clients to initiate their own fund transfers to other banks.

Kevin Mitnick (February 1995) Kevin Mitnick’s computer activities occurred over a number of years during the 1980s and 1990s. Arrested in 1995, he eventually pled guilty to four counts of wire fraud, two counts of computer fraud, and one count of illegally intercepting a wire communication and was sentenced to 46 months in jail. In the plea agreement, Mitnick admitted to having gained unauthorized access to a number of different computer systems belonging to companies such as Motorola, Novell, Fujitsu, and Sun Microsystems. He described using a number of different “tools” and techniques, including social engineering, sniffers, and cloned cellular telephones.

Tech Tip

Intellectual Curiosity In the early days of computer crime, much of the criminal activity centered on gaining unauthorized access to computer systems. In many early cases, the perpetrator of the crime did not intend to cause any damage to the computer but was instead on a quest of “intellectual curiosity”—trying to learn more about computers and networks. Today the ubiquitous nature of computers and networks has eliminated the perceived need for

individuals to break into computers to learn more about them. While there are still those who dabble in hacking for the intellectual challenge, it is more common today for the intellectual curiosity to be replaced by malicious intent. Whatever the reason, today it is considered unacceptable (and illegal) to gain unauthorized access to computer systems and networks.

Omega Engineering and Timothy Lloyd (July 1996) On July 30, 1996, a software “time bomb” went off at Omega Engineering, a New Jersey–based manufacturer of high-tech measurement and control instruments. Twenty days earlier, Timothy Lloyd, a computer network program designer, had been dismissed from the company after a period of growing tension between Lloyd and management at Omega. The program that ran on July 30 deleted all of the design and production programs for the company, severely damaging the small firm and forcing the layoff of 80 employees. The program was eventually traced back to Lloyd, who had left it in retaliation for his dismissal.

Worcester Airport and “Jester” (March 1997) In March of 1997, telephone services to the FAA control tower as well as the emergency services at the Worcester Airport and the community of Rutland, Massachusetts, were cut off for a period of six hours. This disruption occurred as a result of an attack on the phone network by a teenage computer “hacker” who went by the name “Jester.”

The Melissa Virus (March 1999) Melissa is the best known of the early macro-type viruses that attach themselves to documents for programs that have limited macro programming capability. The virus, written and released by David Smith, infected about a million computers and caused an estimated $80 million in damages.

Tech Tip

Speed of Virus Proliferation The speed at which the Slammer worm spread served as a wakeup call to security professionals. It drove home the point that the Internet could be adversely impacted in a matter of minutes. This in turn caused a number of professionals to rethink how prepared they needed to be in order to respond to virus outbreaks in the future. A good first step is to apply patches to systems and software as soon as possible. This will often eliminate the vulnerabilities that the worms and viruses are designed to target.

The Love Letter Virus (May 2000) Also known as the “ILOVEYOU” worm and the “Love Bug,” the Love Letter virus was written and released by a Philippine student named Onel de Guzman. The virus was spread via e-mail with the subject line of “ILOVEYOU.” Estimates of the number of infected machines worldwide have been as high as 45 million, accompanied by a possible $10 billion in damages (it should be noted that figures like these are extremely hard to verify or calculate).

The Code Red Worm (2001) On July 19, 2001, in a period of 14 hours, over 350,000 computers connected to the Internet were infected by the Code Red worm. The cost estimate for how much damage the worm caused (including variations of the worm released on later dates) exceeded $2.5 billion. The vulnerability was a buffer-overflow condition in Microsoft’s IIS web servers, had been known for a month.

The Slammer Worm (2003) On Saturday, January 25, 2003, the Slammer worm was released. It exploited a buffer-overflow vulnerability in computers running Microsoft SQL Server or SQL Server Desktop Engine. Like the vulnerability in Code Red, this weakness was not new and, in fact, had been discovered and a patch released in July of 2002. Within the first 24 hours of Slammer’s release, the worm had infected at least 120,000 hosts and caused network

outages and the disruption of airline flights, elections, and ATMs. At its peak, Slammer-infected hosts were generating a reported 1TB of worm- related traffic every second. The worm doubled its number of infected hosts every 8 seconds. It is estimated that it took less than 10 minutes to reach global proportions and infect 90 percent of the possible hosts it could infect.

Website Defacements (2006) In May of 2006, a Turkish hacker using the handle iSKORPiTX successfully hacked over 21,000 websites in a single effort. The rationale for his actions was never determined, and over the next few years he hacked hundreds of thousands of websites, defacing their cover page with a statement of his hack. A nuisance to some, those affected had to clean up their systems, including repairing vulnerabilities, or he would strike again.

Cyberwar? (2007) In May of 2007, the country of Estonia was crippled by a massive denial- of-service (DoS) cyberattack against all of its infrastructure, firms (banks), and government offices. This attack was traced to IP addresses in Russia, but was never clearly attributed to a government-sanctioned effort.

Operation Bot Roast (2007) In 2007, the FBI announced that it had conducted Operation Bot Roast, identifying over 1 million botnet crime victims. In the process of dismantling the botnets, the FBI arrested several botnet operators across the United States. Although seemingly a big success, this effort made only a small dent in the vast volume of botnets in operation.

Conficker (2008–2009) In late 2008 and early 2009, security experts became alarmed when it was discovered that millions of systems attached to the Internet were infected with the Downadup worm. Also known as Conficker, the worm was

believed to have originated in Ukraine. Infected systems were not initially damaged beyond having their antivirus solution updates blocked. What alarmed experts was the fact that infected systems could be used in a secondary attack on other systems or networks. Each of these infected systems was part of what is known as a bot network (or botnet) and could be used to cause a DoS attack on a target or be used for the forwarding of spam e-mail to millions of users.

U.S. Electric Power Grid (2009) In April 2009, Homeland Security Secretary Janet Napolitano told reporters that the United States was aware of attempts by both Russia and China to break into the U.S. electric power grid, map it out, and plant destructive programs that could be activated at a later date. She indicated that these attacks were not new and had in fact been going on for years. One article in the Kansas City Star, for example, reported that in 1997 the local power company, Kansas City Power and Light, encountered perhaps 10,000 attacks for the entire year. By 2009 the company experienced 30– 60 million attacks.

Try This! Software Patches One of the most effective measures security professionals can take to address attacks on their computer systems and networks is to ensure that all software is up to date in terms of vendor- released patches. Many of the outbreaks of viruses and worms would have been much less severe if everybody had applied security updates and patches when they were released. For the operating system that you use, go to your favorite web browser to find what patches exist for the operating system and what vulnerabilities or issues the patches were created to address.

Fiber Cable Cut (2009) On April 9, 2009, a widespread phone and Internet outage hit the San Jose area in California. This outage was not the result of a group of determined hackers gaining unauthorized access to the computers that operate these

networks, but instead occurred as a result of several intentional cuts in the physical cables that carry the signals. The cuts resulted in a loss of all telephone, cell phone, and Internet service for thousands of users in the San Jose area. Emergency services such as 911 were also affected, which could have had severe consequences.

The Current Threat Environment The threats of the past were smaller, targeted, and in many cases only a nuisance. As time has gone on, more organized elements of cybercrime have entered the picture along with nation-states. From 2009 and beyond, the cyberthreat landscape became considerably more dangerous, with new adversaries out to perform one of two functions: deny you the use of your computer systems, or use your systems for financial gain including theft of intellectual property or financial information including personally identifiable information.

Advanced Persistent Threats Although there are numerous claims as to when advanced persistent threats (APTs) began and who first coined the term, the important issue is to note that APTs represent a new breed of attack pattern. Although specific definitions vary, the three words that comprise the term provide the key elements: advanced, persistent, and threat. Advanced refers to the use of advanced techniques, such as spear phishing, as a vector into a target. Persistent refers to the attacker’s goal of establishing a long-term, hidden position on a system. Many APTs can go on for years without being noticed. Threat refers to the other objective: exploitation. If an adversary invests the resources to achieve an APT attack, they are doing it for some form of long-term advantage. APTs are not a specific type of attack, but rather the new means by which highly resourced adversaries target systems.

GhostNet (2009)

In 2009, the Dalai Lama’s office contacted security experts to determine if it was being bugged. The investigation revealed it was, and the spy ring that was discovered was eventually shown to be spying on over 100 countries’ sensitive missions worldwide. Researchers gave this APT-style spy network the name GhostNet, and although the effort was traced back to China, full attribution was never determined.

Operation Aurora (2009) Operation Aurora was an APT attack first reported by Google, but also targeting Adobe, Yahoo, Juniper Networks, Rackspace, Symantec, and several major U.S. financial and industrial firms. Research analysis pointed to the People’s Liberation Army (PLA) of China as the sponsor. The attack ran for most of 2009 and operated on a large scale, with the groups behind the attack consisting of hundreds of hackers working together against the victim firms.

Stuxnet, Duqu, and Flame (2009–2012) Stuxnet, Duqu, and Flame represent examples of state-sponsored malware. Stuxnet was a malicious worm designed to infiltrate the Iranian uranium enrichment program, to modify the equipment and cause the systems to fail in order to achieve desired results and in some cases even destroy the equipment. Stuxnet was designed to attack a specific model of Siemens programmable logic controller (PLC), which was one of the clues pointing to its objective, the modification of the uranium centrifuges. Although neither the United States nor Israel has admitted to participating in the attack, both have been suggested to have had a role in it. Duqu (2011) is a piece of malware that appears to be a follow-on of

Stuxnet, and has many of the same targets, but rather than being destructive in nature, Duqu is designed to steal information. The malware uses command and control servers across the globe to collect elements such as keystrokes and system information from machines and deliver them to unknown parties.

Flame (2012) is another piece of modular malware that may be a derivative of Stuxnet. Flame is an information collection threat, collecting keystrokes, screenshots, and network traffic. It can record Skype calls and audio signals on a machine. Flame is a large piece of malware with many specific modules, including a kill switch and a means of evading antivirus detection. Because of the open nature of Stuxnet—its source code is widely

available on the Internet—it is impossible to know who is behind Duqu and Flame. In fact, although Duqu and Flame were discovered after Stuxnet, there is growing evidence that they were present before Stuxnet and collected critical intelligence needed to conduct the later attack. The real story behind these malware items is that they demonstrate the power and capability of nation-state malware.

Sony (2011) The hacker group LulzSec reportedly hacked Sony, stealing over 70 million user accounts. The resulting outage lasted 23 days, and cost Sony in excess of $170 million. One of the biggest issues related to the attack was Sony’s poor response, taking more than a week to notify people of the initial attack, and then communicating poorly with its user base during the recovery period. Also notable was that although the credit card data was encrypted on Sony’s servers, the rest of the data stolen was not, making it easy pickings for the disclosure of information.

Saudi Aramco (Shamoon) (2012) In August of 2012, 30,000 computers were shut down in response to a malware attack (named Shamoon) at Saudi Aramco, an oil firm in Saudi Arabia. The attack hit three out of four machines in the firm, and the damage included data wiping of machines and the uploading of sensitive information to Pastebin. It took 10 days for the firm to clean up the infection and restart its business network.

Data Breaches (2013–present) From the end of 2013 through to the time of this writing, data breaches have dominated the security landscape. Target Corporation announced its breach in mid-December, 2013, stating that the hack began as early as “Black Friday” (November 29) and continued through December 15. Data thieves captured names, addresses, and debit and credit card details, including numbers, expiration dates, and CVV codes. In the end a total of 70 million accounts were exposed. Following the Target breach, Home Depot suffered a breach of over 50 million debit and credit card numbers in 2014. JP Morgan Chase also had a major data breach in 2014, announcing the

loss of 77 million account holders’ information. Unlike Target and Home Depot, JP Morgan Chase did not lose account numbers or other crucial data elements. JP Morgan Chase also mounted a major PR campaign touting its security program and spending in order to satisfy customers and regulators of its diligence. At the end of 2014, Sony Pictures Entertainment announced that it had

been hacked, with a massive release of internal data. At the time of this writing, hackers have claimed to have stolen as much as 100 terabytes of data, including e-mails, financial documents, intellectual property, personal data, HR information … in essence, almost everything. Additional reports indicate the destruction of data within Sony; although the extent of the damage is not known, at least one of the elements of malware associated with the attack is known for destroying the Master Boot Record (MBR) of drives. Attribution in the Sony attack is also tricky, as the U.S. government has accused North Korea, while other groups have claimed responsibility, and some investigators claim it was an inside job. It may take years to determine correct attribution, if it is even possible.

Nation-State Hacking (2013–present) Nation-states have become a recognized issue in security, from the Great Firewall of China to modern malware attacks from a wide range of

governments. Threat intelligence became more than a buzzword in 2014 as firms such as CrowdStrike exposed sophisticated hacking actors in China, Russia, and other countries. In 2014 CrowdStrike reported on 39 different threat actors, including criminals, hactivists, state-sponsored groups, and nation-states. Learning how these adversaries act provides valuable clues to their detection in the enterprise. Groups such as China’s Hurricane Panda represent a real security threat. Hurricane Panda focuses on aerospace firms and Internet service companies. Not all threats are from China. Russia is credited with its own share of

malware. Attribution is difficult, and sometimes the only hints are clues, such as the timelines of command and control servers for Energetic Bear, an attack on the energy industry in Europe from the Dragonfly group. The Regin platform, a complete malware platform, possibly in operation for over a decade, has been shown to attack telecom operators, financial institutions, government agencies, and political bodies. Regin is interesting because of its stealth, its complexity, and its ability to hide its command and control network from investigators. Although highly suspected to be deployed by a nation-state, its attribution remains unsolved. In 2015, data breaches and nation-state hacking hit new highs with the

loss of over 20 million sensitive personnel files from the computers at the U.S. Office of Personnel Management (OPM). This OPM loss, reportedly to China, was extremely damaging in that the data loss consisted of the complete background investigations on peoples who had submitted security clearances. These records detailed extensive personal information on the applicants and their family members, providing an adversary with detailed intelligence knowledge. In the same year it was reported that email systems in the Department of State, the Department of Defense, and the White House had been compromised, possibly by both Russia and China. The sensitive nuclear negotiations in Switzerland between the U.S., its allies, and Iran were also reported to have been subject to electronic eavesdropping by parties yet unknown.

Operation Night Dragon was a name given to an intellectual property attack executed against oil, gas, and petrochemical companies in the United States. Using a set of global servers, attackers from China raided global energy companies for proprietary and highly confidential information such as bidding data for leases. The attack shed new light on what constitutes critical data and associated risks.

Threats to Security The incidents described in the previous sections provide a glimpse into the many different threats that face administrators as they attempt to protect their computer systems and networks. There are, of course, the normal natural disasters that organizations have faced for years. In today’s highly networked world, however, new threats have developed that we did not have to worry about 50 years ago. There are a number of ways that we can break down the various threats.

One way to categorize them is to separate threats that come from outside of the organization from those that are internal. Another is to look at the various levels of sophistication of the attacks, from those by “script kiddies” to those by “elite hackers.” A third is to examine the level of organization of the various threats, from unstructured threats to highly structured threats. All of these are valid approaches, and they in fact overlap each other. The following sections examine threats from the perspective of where the attack comes from.

Viruses and Worms While your organization may be exposed to viruses and worms as a result of employees not following certain practices or procedures, generally you will not have to worry about your employees writing or releasing viruses and worms. It is important to draw a distinction between the writers of malware and those who release malware. Debates over the ethics of writing viruses permeate the industry, but currently, simply writing them is

not considered a criminal activity. A virus is like a baseball bat; the bat itself is not evil, but the inappropriate use of the bat (such as to smash a car’s window) falls into the category of criminal activity. (Some may argue that this is not a very good analogy since a baseball bat has a useful purpose—to play ball—but viruses have no useful purpose. In general, this is true, but in some limited environments, such as in specialized computer science courses, the study and creation of viruses can be considered a useful learning experience.)

Cross Check Malware Viruses and worms are just two types of threats that fall under the general heading of malware. The term malware comes from “malicious software,” which describes the overall purpose of code that falls into this category of threat. Malware is software that has a nefarious purpose, designed to cause problems to you as an individual (for example, identity theft) or your system. More information on the different types of malware is provided in Chapter 15.

By number, viruses and worms are the most common problem that an organization faces because literally thousands of them have been created and released. Fortunately, antivirus software and system patching can eliminate the largest portion of this threat. Viruses and worms generally are also nondiscriminating threats; they are released on the Internet in a general fashion and aren’t targeted at a specific organization. They typically are also highly visible once released, so they aren’t the best tool to use in highly structured attacks where secrecy is vital.

Intruders The act of deliberately accessing computer systems and networks without authorization is generally referred to as hacking, with individuals who conduct this activity being referred to as hackers. The term hacking also applies to the act of exceeding one’s authority in a system. This would include authorized users who attempt to gain access to files they aren’t

permitted to access or who attempt to obtain permissions that they have not been granted. While the act of breaking into computer systems and networks has been glorified in the media and movies, the physical act does not live up to the Hollywood hype. Intruders are, if nothing else, extremely patient, since the process to gain access to a system takes persistence and dogged determination. The attacker will conduct many pre-attack activities in order to obtain the information needed to determine which attack will most likely be successful. Typically, by the time an attack is launched, the attacker will have gathered enough information to be very confident that the attack will succeed. Generally, attacks by an individual or even a small group of attackers

fall into the unstructured threat category. Attacks at this level generally are conducted over short periods of time (lasting at most a few months), do not involve a large number of individuals, have little financial backing, and are accomplished by insiders or outsiders who do not seek collusion with insiders. Intruders, or those who are attempting to conduct an intrusion, definitely come in many different varieties and have varying degrees of sophistication (see Figure 1.1). At the low end technically are what are generally referred to as script kiddies, individuals who do not have the technical expertise to develop scripts or discover new vulnerabilities in software but who have just enough understanding of computer systems to be able to download and run scripts that others have developed. These individuals generally are not interested in attacking specific targets, but instead simply want to find any organization that may not have patched a newly discovered vulnerability for which the script kiddie has located a script to exploit the vulnerability. It is hard to estimate how many of the individuals performing activities such as probing networks or scanning individual systems are part of this group, but it is undoubtedly the fastest growing group and the vast majority of the “unfriendly” activity occurring on the Internet is probably carried out by these individuals.

• Figure 1.1 Distribution of attacker skill levels

At the next level are those people who are capable of writing scripts to exploit known vulnerabilities. These individuals are much more technically competent than script kiddies and account for an estimated 8 to 12 percent of malicious Internet activity. At the top end of this spectrum are those highly technical individuals, often referred to as elite hackers, who not only have the ability to write scripts that exploit vulnerabilities but also are capable of discovering new vulnerabilities. This group is the smallest of the lot, however, and is responsible for, at most, only 1 to 2 percent of intrusive activity.

Insiders

It is generally acknowledged by security professionals that insiders are more dangerous in many respects than outside intruders. The reason for this is simple—insiders have the access and knowledge necessary to cause immediate damage to an organization. Most security is designed to protect against outside intruders and thus lies at the boundary between the organization and the rest of the world. Insiders may actually already have all the access they need to perpetrate criminal activity such as fraud. In addition to unprecedented access, insiders also frequently have knowledge of the security systems in place and are better able to avoid detection. Attacks by insiders are often the result of employees who have become disgruntled with their organization and are looking for ways to disrupt operations. It is also possible that an “attack” by an insider may be an accident and not intended as an attack at all. An example of this might be an employee who deletes a critical file without understanding its critical nature.

Tech Tip

The Inside Threat One of the hardest threats that security professionals will have to address is that of the insider. Since employees already have access to the organization and its assets, additional mechanisms need to be in place to detect attacks by insiders and to lessen the ability of these attacks to succeed.

Employees are not the only insiders that organizations need to be concerned about. Often, numerous other individuals have physical access to company facilities. Custodial crews frequently have unescorted access throughout the facility, often when nobody else is around. Other individuals, such as contractors or partners, may have not only physical access to the organization’s facilities but also access to computer systems and networks. A contractor involved in U.S. Intelligence computing, Edward Snowden, was charged with espionage in 2013 after he released a wide range of data illustrating the technical capabilities of U.S.

intelligence surveillance systems. He is the ultimate insider with his name becoming synonymous with the insider threat issue.

Criminal Organizations As businesses became increasingly reliant upon computer systems and networks, and as the amount of financial transactions conducted via the Internet increased, it was inevitable that criminal organizations would eventually turn to the electronic world as a new target to exploit. Criminal activity on the Internet at its most basic is no different from criminal activity in the physical world. Fraud, extortion, theft, embezzlement, and forgery all take place in the electronic environment. One difference between criminal groups and the “average” hacker is the

level of organization that criminal elements employ in their attack. Criminal groups typically have more money to spend on accomplishing the criminal activity and are willing to spend extra time accomplishing the task provided the level of reward at the conclusion is great enough. With the tremendous amount of money that is exchanged via the Internet on a daily basis, the level of reward for a successful attack is high enough to interest criminal elements. Attacks by criminal organizations usually fall into the structured threat category, which is characterized by a greater amount of planning, a longer period of time to conduct the activity, more financial backing to accomplish it, and possibly corruption of, or collusion with, insiders.

Nation-States, Terrorists, and Information Warfare As nations have increasingly become dependent on computer systems and networks, the possibility that these essential elements of society might be targeted by organizations or nations determined to adversely affect another nation has become a reality. Many nations today have developed to some extent the capability to conduct information warfare. There are several definitions for information warfare, but a simple one is that it is warfare conducted against the information and information processing equipment used by an adversary. In practice, this is a much more complicated subject,

because information not only may be the target of an adversary, but also may be used as a weapon. Whatever definition you use, information warfare falls into the highly structured threat category. This type of threat is characterized by a much longer period of preparation (years is not uncommon), tremendous financial backing, and a large and organized group of attackers. The threat may include attempts not only to subvert insiders but also to plant individuals inside of a potential target in advance of a planned attack.

Tech Tip

Information Warfare Once only the concern of governments and the military, information warfare today can involve many other individuals. With the potential to attack the various civilian-controlled critical infrastructures, security professionals in nongovernmental sectors today must also be concerned about defending their systems against attack by agents of foreign governments.

An interesting aspect of information warfare is the list of possible targets available. We have grown accustomed to the idea that, during war, military forces will target opposing military forces but will generally attempt to destroy as little civilian infrastructure as possible. In information warfare, military forces are certainly still a key target, but much has been written about other targets, such as the various infrastructures that a nation relies on for its daily existence. Water, electricity, oil and gas refineries and distribution, banking and finance, telecommunications—all fall into the category of critical infrastructures for a nation. Critical infrastructures are those whose loss would have severe repercussions on the nation. With countries relying so heavily on these infrastructures, it is inevitable that they will be viewed as valid targets during conflict. Given how dependent these infrastructures are on computer systems and networks, it is also inevitable that these same computer systems and networks will be targeted for a cyberattack in an information war.

As demonstrated by the Stuxnet attacks, and the cyberattacks in Estonia, the risk of nation-state attacks is real. There have been numerous accusations of intellectual property theft being sponsored by, and in some cases even performed by, nation-state actors. In a world where information dominates government, business, and economies, the collection of information is the key to success, and with large rewards, the list of characters willing to spend significant resources is high.

Security Trends The biggest change affecting computer security that has occurred over the last 30 years has been the transformation of the computing environment from large mainframes to a highly interconnected network of smaller systems. This interconnection of systems is the Internet and it now touches virtually all systems. What this has meant for security is a switch from a closed operating environment in which everything was fairly contained to one in which access to a computer can occur from almost anywhere on the planet. This has, for obvious reasons, greatly complicated the job of the security professional. The type of individual who attacks a computer system or network has

also evolved over the last 30 years. As illustrated by the sample of attacks listed previously, the attackers have become more focused on gain over notoriety. Today computer attacks are used to steal and commit fraud and other crimes in the pursuit of monetary enrichment. Computer crimes are big business today, not just because it is hard to catch the perpetrators, but also because the number of targets is large and the rewards greater than robbing local stores. Over the past several years a wide range of computer industry firms

have begun issuing annual security reports. Among these firms is Verizon, which has issued its annual Data Breach Investigations Report (DBIR) since 2008 and is lauded because of its breadth and depth. The 2015 DBIR was based on over 2,100 data breaches and 79,790 security incidents in 61 countries. Perhaps the most valuable aspect of the DBIR is its

identification of common details that result in a data breach. The Verizon DBIRs are available at www.verizonenterprise.com/DBIR/

In the early days of computers, security was considered to be a binary condition in which your system was either secure or not secure. Security efforts were made to achieve a state of security, meaning that the system was secure. Today, the focus has changed. In light of the revelation that a pure state of security is not achievable in the binary sense, the focus has shifted to one of risk management. Today, the question is how much risk your system is exposed to, and from what sources.

Targets and Attacks There are two general reasons a particular computer system is attacked: either it is specifically targeted by the attacker, or it is an opportunistic target.

Specific Target In this case, the attacker has chosen the target not because of the hardware or software the organization is running but for another reason, perhaps a political reason. An example of this type of attack would be an individual in one country attacking a government system in another. Alternatively, the attacker may be targeting the organization as part of a hacktivist attack. For example, an attacker may deface the web site of a company that sells fur coats because the attacker feels that using animals in this way is unethical. Perpetrating some sort of electronic fraud is another reason a specific system might be targeted. Whatever the reason, an attack of this nature is decided upon before the attacker knows what hardware and software the organization has.

The motive behind most computer attacks falls into one of two categories: 1. To deprive someone the use of their system. 2. To use someone else’s system to enrich oneself. In some cases, the use of a denial-of-service attack (item 1) precedes the actual heist (item 2).

Opportunistic Target The second type of attack, an attack against a target of opportunity, is conducted against a site that has software that is vulnerable to a specific exploit. The attackers, in this case, are not targeting the organization; instead, they have learned of a vulnerability and are simply looking for an organization with this vulnerability that they can exploit. This is not to say that an attacker might not be targeting a given sector and looking for a target of opportunity in that sector, however. For example, an attacker may desire to obtain credit card or other personal information and may search for any exploitable company with credit card information in order to carry out the attack. Targeted attacks are more difficult and take more time than attacks on a

target of opportunity. The latter simply relies on the fact that with any piece of widely distributed software, there will almost always be somebody who has not patched the system (or has not patched it properly) as they should have.

Minimizing Possible Avenues of Attack Understanding the steps an attacker will take enables you to limit the exposure of your system and minimize those avenues an attacker might possibly exploit. There are multiple elements to a solid computer defense, but two of the key elements involve limiting an attacker’s avenues of attack. The first step an administrator can take to reduce possible attacks is to ensure that all patches for the operating system and applications are

installed. Many security problems that we read about, such as viruses and worms, exploit known vulnerabilities for which patches exist. The reason such malware caused so much damage in the past was that administrators did not take the appropriate actions to protect their systems. The second step an administrator can take is system hardening, which

involves limiting the services that are running on the system. Only using those services that are absolutely needed does two things: it limits the possible avenues of attack (those services with vulnerabilities that can be exploited), and it reduces the number of services the administrator has to worry about patching in the first place. This is one of the important first steps any administrator should take to secure a computer system. System hardening is covered in detail in Chapter 14. While there are no iron-clad defenses against attack, or guarantees that

an attack won’t be successful, you can take steps to reduce the risk of loss. This is the basis for the change in strategy from a defense-based one to one based on risk management. Risk management is covered in detail in Chapter 20.

Approaches to Computer Security While much of the discussion of computer security focuses on how systems are attacked, it is equally important to consider the structure of defenses. There are three major considerations when securing a system:

Correctness Ensuring that a system is fully up to date, with all patches installed and proper security controls in place; this goes a long way toward minimizing risk. Correctness begins with a secure development lifecycle (covered in Chapter 18), continues through patching and hardening (Chapters 14 and 21), and culminates in operations (Chapters 3, 4, 19, and 20).

Isolation Protecting a system from unauthorized use, by means of access control and physical security. Isolation begins with

infrastructure (covered in Chapters 9 and 10), continues with access control (Chapters 8, 11, and 12), and includes the use of cryptography (Chapters 5, 6, and 7).

Obfuscation Making it difficult for an adversary to know when they have succeeded. Whether accomplished by obscurity, randomization, or obfuscation, increasing the workload of an attacker makes it more difficult for them to succeed in their attack. Obfuscation occurs throughout all topics, as it is a built-in element, whether in the form of random numbers in crypto or address space randomizations, stack guards, or pointer encryption at the operating system level.

Each of these approaches has its inherent flaws, but taken together, they can provide a strong means of system defense.

Ethics Any meaningful discussion about operational aspects of information security must include the topic of ethics. Ethics is commonly defined as a set of moral principles that guides an individual’s or group’s behavior. Because information security efforts frequently involve trusting people to keep secrets that could cause harm to the organization if revealed, trust is a foundational element in the people side of security. And trust is built upon a code of ethics, a norm that allows everyone to understand expectations and responsibilities. There are several different ethical frameworks that can be applied to making a decision, and these are covered in detail in Chapter 25. Ethics is a difficult topic; separating right from wrong is easy in many

cases, but in other cases it is more difficult. For example, writing a virus that damages a system is clearly bad behavior, but is writing a worm that goes out and patches systems, without the users’ permission, right or wrong? Does the ends justify the means? Such questions are the basis of ethical discussions that define the challenges faced by security personnel

on a regular basis.

Additional References 1. http://en.wikipedia.org/wiki/Timeline_of_computer_security_hacker_history 2. http://www.informationisbeautiful.net/visualizations/worlds-biggest-

data-breaches-hacks/www.verizonenterprise.com/DBIR/

Chapter 1 Review

Chapter Summary After reading this chapter and completing the quizzes, you should understand the following regarding security threats and trends.

Define computer security

Computer security is defined by operating in a manner where the system does what it is supposed to do and only what it is supposed to do.

Information security is defined by the information being protected from unauthorized access or alteration and yet is available to authorized individuals when required.

Discuss common threats and recent computer crimes that have been committed

There are a number of different threats to security, including viruses and worms, intruders, insiders, criminal organizations, terrorists, and information warfare conducted by foreign countries.

There are two general reasons a particular computer system is attacked: it is specifically targeted by the attacker, or it is a target of opportunity.

Targeted attacks are more difficult and take more time than attacks on a target of opportunity.

The different types of electronic crime fall into two main categories: crimes in which the computer was the target of the attack, and incidents in which the computer was a means of perpetrating a criminal act.

One significant trend observed over the last several years has been the increase in the number of computer attacks and their effectiveness.

List and discuss recent trends in computer security

There are many different ways to attack computers and networks to take advantage of what has made shopping, banking, investment, and leisure pursuits a simple matter of “dragging and clicking” for many people.

The biggest change that has occurred in security over the last 30 years has been the transformation of the computing environment from large mainframes to a highly interconnected network of much smaller systems.

Describe common avenues of attacks

An attacker can use a common technique against a wide range of targets in an opportunistic attack, only succeeding where the attack is viable.

An attacker can employ a variety of techniques against a specific target when it is desired to obtain access to a specific system.

Describe approaches to computer security

There are three main approaches an enterprise can employ, one based on correctness, one involving isolation, and one involving obfuscation.

The ideal method is to employ all three together.

Discuss the relevant ethical issues associated with computer security

Ethics is commonly defined as a set of moral principles that guides an individual’s or group’s behaviors.

Because information security efforts frequently involve trusting people to keep secrets that could cause harm to the organization if revealed, trust is a foundational element in the people side of security.

Key Terms computer security (1) critical infrastructure (11) elite hacker (9) hacker (9) hacking (9) hacktivist (12) highly structured threat (11) information warfare (10) script kiddie (9) structured threat (10) unstructured threat (9)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. A(n) _______________ is characterized by a greater amount of planning, a longer period of time to conduct the activity, more financial backing to accomplish it, and the possible corruption of, or

collusion with, insiders.

2. A hacker whose activities are motivated by a personal cause or position is known as a(n) _______________.

3. A(n) _______________ is one whose loss would have a severe detrimental impact on the nation.

4. _______________ is conducted against the information and information processing equipment used by an adversary.

5. Actors who deliberately access computer systems and networks without authorization are called _______________ .

6. A(n) _______________ generally is short-term in nature, does not involve a large group of individuals, does not have large financial backing, and does not include collusion with insiders.

7. A(n) _______________ is a highly technically competent individual who conducts intrusive activity on the Internet and is capable of not only exploiting known vulnerabilities but also finding new vulnerabilities.

8. The act of deliberately accessing computer systems and networks without authorization is generally referred to as _______________.

9. A(n) _______________ is an individual who does not have the technical expertise to develop scripts or discover new vulnerabilities in software but who has just enough understanding of computer systems to be able to download and run scripts that others have developed.

10. A(n) _______________ is characterized by a much longer period of preparation (years is not uncommon), tremendous financial backing, and a large and organized group of attackers.

Multiple-Choice Quiz

1. Which threats are characterized by possibly long periods of preparation (years is not uncommon), tremendous financial backing, a large and organized group of attackers, and attempts to subvert insiders or to plant individuals inside a potential target in advance of a planned attack?

A. Unstructured threats

B. Structured threats

C. Highly structured threats

D. Nation-state information warfare threats

2. In which of the following is an attacker looking for any organization vulnerable to a specific exploit rather than attempting to gain access to a specific organization?

A. Target of opportunity attack

B. Targeted attack

C. Vulnerability scan attack

D. Information warfare attack

3. The rise of which of the following has greatly increased the number of individuals who probe organizations looking for vulnerabilities to exploit?

A. Virus writers

B. Script kiddies

C. Hackers

D. Elite hackers

4. For what reason(s) do some security professionals consider insiders more dangerous than outside intruders?

A. Employees (insiders) are easily corrupted by criminal and other

organizations.

B. Insiders have the access and knowledge necessary to cause immediate damage to the organization.

C. Insiders have knowledge of the security systems in place and are better able to avoid detection.

D. Both B and C

5. The act of deliberately accessing computer systems and networks without authorization is generally known as:

A. Computer intrusion

B. Hacking

C. Cracking

D. Probing

6. What is the most common problem/threat an organization faces? A. Viruses/worms

B. Script kiddies

C. Hackers

D. Hacktivists

7. Warfare conducted against the information and information processing equipment used by an adversary is known as:

A. Hacking

B. Cyberterrorism

C. Information warfare

D. Network warfare

8. An attacker who feels that using animals to make fur coats is

unethical and thus defaces the web site of a company that sells fur coats is an example of:

A. Information warfare

B. Hacktivisim

C. Cyber crusading

D. Elite hacking

9. Criminal organizations would normally be classified as what type of threat?

A. Unstructured

B. Unstructured but hostile

C. Structured

D. Highly structured

10. Which of the following individuals have the ability to not only write scripts that exploit vulnerabilities but also discover new vulnerabilities?

A. Elite hackers

B. Script kiddies

C. Hacktivists

D. Insiders

Essay Quiz 1. Reread the various examples of computer crimes at the beginning of

this chapter. Categorize each as either a crime where the computer was the target of the criminal activity or a crime in which the computer was a tool in accomplishing the criminal activity.

2. A friend of yours has just been hired by an organization as its computer security officer. Your friend is a bit nervous about this new job and has come to you, knowing that you are taking a computer security class, to ask your advice on measures that can be taken that might help prevent an intrusion. What three things can you suggest that are simple but can tremendously help limit the possibility of an attack?

3. Discuss the major difference between a target of opportunity attack and a targeted attack. Which do you believe is the more common one?

Lab Project

• Lab Project 1.1 A number of different examples of computer crimes were discussed in this chapter. Similar activities seem to happen daily. Do a search on the Internet to see what other examples you can find. Try and obtain the most recent examples possible.

chapter 2 General Security Concepts

I

“A people that values its privileges above its principles soon loses both.”

—DWIGHT D. EISENHOWER

In this chapter, you will learn how to

Define basic terms associated with computer and information security

Identify the basic approaches to computer and information security

Identify the basic principles of computer and information security

Distinguish among various methods to implement access controls

Describe methods used to verify the identity and authenticity of an individual

Recognize some of the basic models used to implement security in operating systems

n Chapter 1, you learned about some of the various threats that we, as security professionals, face on a daily basis. In this chapter, you start exploring the field of computer security. Computer security has a series

of fundamental concepts that support the discipline. In this chapter we will begin with an examination of security models and concepts and proceed to see how they are operationally employed.

Basic Security Terminology The term hacking has been used frequently in the media. A hacker was once considered an individual who understood the technical aspects of computer operating systems and networks. Hackers were individuals you turned to when you had a problem and needed extreme technical expertise. Today, primarily as a result of the media, the term is used more often to refer to individuals who attempt to gain unauthorized access to computer systems or networks. While some would prefer to use the terms cracker and cracking when referring to this nefarious type of activity, the terminology generally accepted by the public is that of hacker and hacking. A related term that may sometimes be seen is phreaking, which refers to

the “hacking” of the systems and computers used by a telephone company to operate its telephone network.

The field of computer security constantly evolves, introducing new terms frequently, which are often coined by the media. Make sure to learn the meaning of terms such as hacking, phreaking, vishing, phishing, pharming, and spear phishing. Some of these have been around for many years, such as hacking, whereas others have appeared only in the last few years, such as spear phishing.

Security Basics Computer security itself is a term that has many meanings and related terms. Computer security entails the methods used to ensure that a system is secure. Subjects such as authentication and access controls must be addressed in broad terms of computer security. Seldom in today’s world are computers not connected to other computers in networks. This then introduces the term network security to refer to the protection of the multiple computers and other devices that are connected together. Related to these two terms are two others: information security and information assurance, which place the focus of the security process not on the hardware and software being used but on the data that is processed by them. Assurance also introduces another concept, that of the availability of the systems and information when we want them. The common press and many professionals have settled on cybersecurity as the term to describe the field. Still another term that may be heard in the security world is COMSEC, which stands for communications security and deals with the security of telecommunication systems. Cybersecurity has become regular headline news these days, with

reports of break-ins, data breaches, fraud, and a host of other calamities. The general public has become increasingly aware of its dependence on computers and networks and consequently has also become interested in

the security of these same computers and networks. As a result of this increased attention by the public, several new terms have become commonplace in conversations and print. Terms such as hacking, virus, TCP/IP, encryption, and firewalls are now frequently encountered in mainstream news media and have found their way into casual conversations. What was once the purview of scientists and engineers is now part of our everyday life. With our increased daily dependence on computers and networks to

conduct everything from making purchases at our local grocery store, banking, trading stocks, and receiving medical treatment to driving our children to school, ensuring that computers and networks are secure has become of paramount importance. Computers and the information they manipulate has become a part of virtually every aspect of our lives.

The “CIA” of Security Almost from its inception, the goal of computer security has been threefold: confidentiality, integrity, and availability—the “CIA” of security. The purpose of confidentiality is to ensure that only those individuals who have the authority to view a piece of information may do so. No unauthorized individual should ever be able to view data they are not entitled to access. Integrity is a related concept but deals with the generation and modification of data. Only authorized individuals should ever be able to create or change (or delete) information. The goal of availability is to ensure that the data, or the system itself, is available for use when the authorized user wants it.

Tech Tip

CIA of Security While there is no universal agreement on authentication, auditability, and nonrepudiation as additions to the original CIA of security, there is little debate over whether confidentiality, integrity, and availability are basic security principles. Understand these principles, because one or more of them are the reason most security hardware, software, policies, and

procedures exist.

As a result of the increased use of networks for commerce, two additional security goals have been added to the original three in the CIA of security. Authentication attempts to ensure that an individual is who they claim to be. The need for this in an online transaction is obvious. Related to this is nonrepudiation, which deals with the ability to verify that a message has been sent and received and that the sender can be identified and verified. The requirement for this capability in online transactions should also be readily apparent. Recent emphasis on systems assurance has raised the potential inclusion of the term auditability, which refers to whether a control can be verified to be functioning properly. In security, it is imperative that we can track actions to ensure what has or has not been done.

The Operational Model of Computer Security For many years, the focus of security was on prevention. If we could prevent everyone who did not have authorization from gaining access to our computer systems and networks, then we assumed that we had achieved security. Protection was thus equated with prevention. While the basic premise of this is true, it fails to acknowledge the realities of the networked environment our systems are part of. No matter how well we seem to do in prevention technology, somebody always seems to find a way around our safeguards. When this happens, our system is left unprotected. Thus, we need multiple prevention techniques and also technology to alert us when prevention has failed and to provide ways to address the problem. This results in a modification to our original security equation with the addition of two new elements—detection and response. Our security equation thus becomes:

Protection = Prevention + (Detection + Response) This is known as the operational model of computer security. Every security technique and technology falls into at least one of the three

elements of the equation. Examples of the types of technology and techniques that represent each are depicted in Figure 2.1.

• Figure 2.1 Sample technologies in the operational model of computer security

Cybersecurity Framework Model In 2013, President Obama signed an executive order directing the U.S. National Institute of Science and Technology (NIST) to work with industry and develop a cybersecurity framework. This was in response to several significant cybersecurity events where the victim companies appeared to be unprepared. The resulting framework, titled Framework for Improving Critical Infrastructure Cybersecurity, was created as a voluntary system, based on existing standards, guidelines, and practices, to facilitate adoption and acceptance across a wide array of industries.

Tech Tip

Cybersecurity Framework The NIST Cybersecurity Framework is a risk-based approach to implementation of cybersecurity activities in an enterprise. The framework provides a common taxonomy of standards, guidelines, and practices that can be employed to strengthen cybersecurity efforts. The framework can be obtained from NIST:

www.nist.gov/cyberframework/upload/cybersecurity-framework-021214-final.pdf

The Cybersecurity Framework provides a common taxonomy and mechanism to assist in aligning management practices with existing standards, guidelines, and practices. Its purpose is to complement and enhance risk management efforts through

1. Determining their current cybersecurity posture 2. Documenting their desired target state with respect to cybersecurity 3. Determining and prioritizing improvement and corrective actions 4. Measuring and monitoring progress toward goals 5. Creating a communication mechanism for coordination among stakeholders

The framework is composed of five core functions, as illustrated in Figure 2.2. Two of these core functions, Identify and Protect, describe actions taken before an incident. Detect is the core function associated with intrusion detection or the beginning of an incident response. The last two, Respond and Recover, detail actions that take place during the post- incident response. Examples of the items under each function are illustrated in the figure. In addition to the five functions, the framework has levels of implementations referred to as tiers. These tiers represent the organization’s ability from Partial (Tier 1) to Adaptive (Tier 4).

• Figure 2.2 Cybersecurity Framework core functions

Security Tenets In addition to the CIA elements, there are additional tenets that form a basis for system security. The three operational tenets found in secure deployments are session management, exception management, and configuration management.

Session Management Session management is the set of activities employed to establish a communication channel between two parties, identifying each in a manner that allows future activity without renewed authentication. Session management allows an application to authenticate once and have subsequent activities ascribed to the authenticated user. Sessions are frequently used in web applications to preserve state and user information between normally stateless clicks. Sessions are typically identified by an ID that is known to both sides of

the conversation. This ID can be used as a token for future identification. If confidentiality is required, then the channel should be secured by an appropriate level of cryptographic protection.

Tech Tip

Session Management Cheat Sheet Session management is a common task for web applications, and the Open Web Application Security Project (OWASP) has a cheat sheet to assist in the correct implementation of session management. See https://www.owasp.org/index.php/Session_Management_Cheat_Sheet.

Session management includes all the activities necessary to manage the session, from establishment, during use, and at completion of the conversation. Because the session represents the continuity of a security

condition established during authentication, the level of protection that should be afforded to the session ID should be commensurate with the level of security initially established.

Exception Management Exceptions are the invocation of conditions that fall outside the normal sequence of operation. Whether by error or malicious action, exceptions are changes to normal processing and need to be managed. The special processing required by conditions that fall outside normal parameters can result in errors either locally or in follow-on processes in a system. The handling of exceptions, referred to as exception handling, is an important consideration during software development. Exception management is more than just exception handling in software

development. When the operation of a system encounters an exception, whether it is invoked by a person, process, technology, or combination, the system must effectively handle the condition. This can mean many different things, sometimes even operating outside normal policy limits. Exception management can also be nontechnical in nature: systems or environments that cannot follow organizational security policy, for example, must be documented, exceptions must be approved, and mitigations must be put in place to lower the risk associated with exceptions to policy. The bottom line is simple: either the system must handle the condition and recover, or it must fail and be recovered by separate action. Designing in exception handling makes a system more resilient, because exceptions will happen, and how they are handled is the only unknown outcome.

Configuration Management Configuration management is key to the proper operation of IT systems. IT systems are first and foremost systems, groups of elements that work together to achieve a desired resultant process. The proper configuration and provisioning of all of the components in a system is essential to the proper operation of the system. The design and operation of the elements

to ensure the proper functional environment of a system is referred to as configuration management. Configuration management is a key operation principle and is thoroughly covered in Chapter 21.

Security Approaches There are multiple approaches an organization can take to address the protection of its networks: ignore security issues, provide host security, provide network-level security, or provide a combination of the latter two. The middle two, host security and network-level security, have prevention as well as detection and response components. Rather than view these two approaches as independent solutions, a mature organization uses both in a complementary fashion. If an organization decides to ignore security, it has chosen to utilize the

minimal amount of security that is provided with its workstations, servers, and devices. No additional security measures will be implemented. Each “out of the box” system has certain security settings that can be configured, and they should be. To actually protect an entire network, however, requires work in addition to the few protection mechanisms that come with systems by default.

Tech Tip

Got Network? A classic black T-shirt in the security industry says “got root?” It’s a takeoff on the successful ad campaign “got milk?” and indicates the power of root privilege. Similar to “got root?” is “got network?”, for if you truly “own” the network, then you have significant control over what passes across it and can result in information disclosure. To ensure a secure posture, both network and host access levels must be controlled.

Host Security Host security takes a granular view of security by focusing on protecting

each computer and device individually instead of addressing protection of the network as a whole. When host security is used, each computer is relied upon to protect itself. If an organization decides to implement only host security and does not include network security, there is a high probability of introducing or overlooking vulnerabilities. Most environments are filled with different operating systems (Windows, UNIX, Linux, OS X), different versions of those operating systems, and different types of installed applications. Each operating system has security configurations that differ from those of other systems, and different versions of the same operating system may in fact have configuration variations between them. Host security is important and should always be addressed. Security,

however, should not stop there, as host security is a complementary process to be combined with network security. If individual host computers have vulnerabilities embodied within them, then network security can provide another layer of protection that will, hopefully, stop any intruders who have gotten that far into the environment.

A longtime discussion has centered on whether host- or network-based security is more important. Most security experts now generally agree that a combination of both is needed to adequately address the wide range of possible security threats. Certain attacks are more easily spotted and some attacks are more easily prevented using tools designed for one or the other of these approaches.

Network Security In some smaller environments, host security by itself may be an option, but as systems become connected into networks, security should include the actual network itself. In network security, an emphasis is placed on controlling access to internal computers from external entities. This control can be through devices such as routers, firewalls, authentication hardware and software, encryption, and intrusion detection systems (IDSs).

Network environments tend to be unique entities because usually no two networks have exactly the same number of computers, the same applications installed, the same number of users, the exact same configurations, or the same available servers. They will not perform the same functions or have the same overall architecture. Since networks have so many variations, there are many different ways in which they can be protected and configured. This chapter covers some foundational approaches to network and host security. Each approach may be implemented in a myriad of ways, but both network and host security need to be addressed for an effective total security program.

Tech Tip

Security Design Principles The eight design principles from Saltzer and Schroeder are listed and paraphrased here:

Least privilege Use minimum privileges necessary to perform a task.

Separation of privilege Access should be based on more than one item. Fail-safe defaults Deny by default (implicit deny) and only grant access with explicit permission.

Economy of mechanism Mechanisms should be small and simple. Complete mediation Protection mechanisms should cover every access to every object.

Open design Protection mechanisms should not depend upon secrecy of the mechanism itself.

Least common mechanism Protection mechanisms should be shared to the least degree possible among users.

Psychological acceptability Protection mechanisms should not impact users, or if they do, the impact should be minimal.

Ref: J.H. Saltzer and M.D. Schroeder, “The Protection of Information in Computer Systems,” Proc. IEEE, vol. 63, no. 9, 1975, pp. 1278–1308.

Security Principles

In the mid-1970s, two computer scientists from MIT, Jerome Saltzer and Michael Schroeder, published a paper on design principles for a secure computer system. The Saltzer and Schroeder paper, titled “The Protection of Information in Computer Systems,” has been hailed as a seminal work in computer security, and the eight design principles are as relevant today as they were in 1970s. These principles are useful in secure system design and operation.

Least Privilege One of the most fundamental principles in security is least privilege. This concept is applicable to many physical environments as well as network and host security. Least privilege means that a subject (which may be a user, application, or process) should have only the necessary rights and privileges to perform its task with no additional permissions. Limiting an object’s privileges limits the amount of harm that can be caused, thus limiting an organization’s exposure to damage. Users may have access to the files on their workstations and a select set of files on a file server, but no access to critical data that is held within the database. This rule helps an organization protect its most sensitive resources and helps ensure that whoever is interacting with these resources has a valid reason to do so.

Try This! Examples of the Least Privilege Principle The security concept of least privilege is not unique to computer security. It has been practiced by organizations such as financial institutions and governments for centuries. Basically it simply means that individuals are given only the absolute minimum of privileges that are required to accomplish their assigned job. Examine the security policies that your organization has in place and see if you can identify examples of where the principle of least privilege has been used.

The concept of least privilege applies to more network security issues than just providing users with specific rights and permissions. When trust relationships are created, they should not be implemented in such a way

that everyone trusts each other simply because it is easier. One domain should trust another for very specific reasons, and the implementers should have a full understanding of what the trust relationship allows between two domains. If one domain trusts another, do all of the users automatically become trusted, and can they thus easily access any and all resources on the other domain? Is this a good idea? Is there a more secure way of providing the same functionality? If a trusted relationship is implemented such that users in one group can access a plotter or printer that is available on only one domain, it might make sense to simply purchase another plotter so that other, more valuable or sensitive resources are not accessible by the entire group. Another issue that falls under the least privilege concept is the security

context in which an application runs. All applications, scripts, and batch files run in the security context of a specific user on an operating system. They execute with specific permissions as if they were a user. The application may be Microsoft Word and run in the space of a regular user, or it may be a diagnostic program that needs access to more sensitive system files and so must run under an administrative user account, or it may be a program that performs backups and so should operate within the security context of a backup operator. The crux of this issue is that a program should execute only in the security context that is needed for that program to perform its duties successfully. In many environments, people do not really understand how to make programs run under different security contexts, or it may just seem easier to have all programs run under the administrator account. If attackers can compromise a program or service running under the administrator account, they have effectively elevated their access level and have much more control over the system and many more ways to cause damage.

Try This! Control of Resources Being able to apply the appropriate security control to file and print resources is an important

aspect of the least privilege security principle. How this is implemented varies depending on the operating system that the computer runs. Check how the operating system that you use provides for the ability to control file and print resources.

Separation of Privilege Protection mechanisms can be employed to grant access based on a variety of factors. One of the key principles is to base decisions on more than a single piece of information. The principle of separation of privilege states that the protection mechanism should be constructed so that it uses more than one piece of information to make access decisions. Applying this principle to the people side of the security function results in the concept of separation of duties. The principle of separation of privilege is applicable to physical

environments as well as network and host security. When applied to people’s actions, separation of duties specifies that for any given task, more than one individual needs to be involved. The task is broken into different duties, each of which is accomplished by a separate individual. By implementing a task in this manner, no single individual can abuse the system for his or her own gain. This principle has been implemented in the business world, especially financial institutions, for many years. A simple example is a system in which one individual is required to place an order and a separate person is needed to authorize the purchase. While separation of duties provides a certain level of checks and

balances, it is not without its own drawbacks. Chief among these is the cost required to accomplish the task. This cost is manifested in both time and money. More than one individual is required when a single person could accomplish the task, thus potentially increasing the cost of the task. In addition, with more than one individual involved, a certain delay can be expected because the task must proceed through its various steps.

Fail-Safe Defaults Today, the Internet is no longer the friendly playground of researchers that it once was. This has resulted in different approaches that might at first

seem less than friendly but that are required for security purposes. Fail- safe defaults is a concept that when something fails, it should do so to a safe state. One approach is that a protection mechanism should deny access by default, and grant access only when explicit permission exists. This is sometimes called default deny, and the common operational term for this approach is implicit deny. Frequently in the network world, administrators make many decisions

concerning network access. Often a series of rules will be used to determine whether or not to allow access (which is the purpose of a network firewall). If a particular situation is not covered by any of the other rules, the implicit deny approach states that access should not be granted. In other words, if no rule would allow access, then access should not be granted. Implicit deny applies to situations involving both authorization and access. The alternative to implicit deny is to allow access unless a specific rule

forbids it. Another example of these two approaches is in programs that monitor and block access to certain web sites. One approach is to provide a list of specific sites that a user is not allowed to access. Access to any site not on the list would be implicitly allowed. The opposite approach (the implicit deny approach) would block all access to sites that are not specifically identified as authorized. As you can imagine, depending on the specific application, one or the other approach will be more appropriate. Which approach you choose depends on the security objectives and policies of your organization.

Implicit deny is another fundamental principle of security and students need to be sure that they understand this principle. Similar to least privilege, this principle states that if you haven’t specifically been allowed access, then it should be denied.

Economy of Mechanism

The terms security and complexity are often at odds with each other, because the more complex something is, the harder it is to understand, and you cannot truly secure something if you do not understand it. Another reason complexity is a problem within security is that it usually allows too many opportunities for something to go wrong. If an application has 4000 lines of code, there are a lot fewer places for buffer overflows, for example, than in an application of two million lines of code. The principle of economy of mechanism is described as always using simple solutions when available.

Keep it simple: Another method of looking at the principle of economy of mechanism is that the protection mechanism should be small and simple.

An example of the principle concerns the number of services that you allow your system to run. Default installations of computer operating systems often leave many services running. The keep-it-simple principle tells us to eliminate or disable those services that we don’t need. This is also a good idea from a security standpoint because it results in fewer applications that can be exploited and fewer services that the administrator is responsible for securing. The general rule of thumb is to eliminate or disable all nonessential services and protocols. This of course leads to the question, how do you determine whether a service or protocol is essential or not? Ideally, you should know what your computer system or network is being used for, and thus you should be able to identify and activate only those elements that are essential. For a variety of reasons, this is not as easy as it sounds. Alternatively, a stringent security approach that one can take is to assume that no service is necessary (which is obviously absurd) and activate services and ports only as they are requested. Whatever approach is taken, there is a never-ending struggle to try to strike a balance between providing functionality and maintaining security.

Complete Mediation One of the fundamental tenets of a protection system is to check all access requests for permission. Each and every time a subject requests access to an object, the permission must be checked; otherwise an attacker might gain unauthorized access to an object. Complete mediation refers to the concept that each and every request should be verified. When permissions are verified the first time, and the result is cached for subsequent use, performance may be increased, but this also opens the door to permission errors. Should a permission change subsequent to the first use, this change would not be applied to the operations after the initial check. Complete mediation also refers to ensuring that all operations go

through the protection mechanism. When security controls are added after the fact, it is important to make certain that all process flows are covered by the controls, including exceptions and out-of-band requests. If an automated process is checked in one manner, but a manual paper backup process has a separate path, it is important to ensure all checks are still in place. When a system undergoes disaster recovery or business continuity processes, or backup and/or restore processes, these too require complete mediation.

Open Design The principle of open design holds that the protection of an object should not rely upon secrecy of the protection mechanism itself. This principle has been long proven in cryptographic circles, where hiding the algorithm ultimately fails and the true protection relies upon the secrecy and complexity of the keys. The principle does not exclude the idea of using secrecy, but merely states that, on the face of it, secrecy of mechanism is not sufficient for protection. Another concept in security that should be discussed in this context is

the idea of security through obscurity. In this case, security is considered effective if the environment and protection mechanisms are confusing or thought to be not generally known. Security through obscurity uses the

approach of protecting something by hiding it. Noncomputer examples of this concept include hiding your briefcase or purse if you leave it in the car so that it is not in plain view, hiding a house key under a doormat or in a planter, or pushing your favorite ice cream to the back of the freezer so that everyone else thinks it is all gone. The idea is that if something is out of sight, it is out of mind. This approach, however, does not provide actual protection of the object. Someone can still steal the purse by breaking into the car, lift the doormat and find the key, or dig through the items in the freezer to find your favorite ice cream. Security through obscurity may make someone work a little harder to accomplish a task, but it does not prevent anyone from eventually succeeding.

Tech Tip

Security Through Obscurity The principle of open design and the practice of security by obscurity may seem at odds with each other, but in reality they are not. The principle of open design states that secrecy itself cannot be relied upon as a means of protection. The practice of security through obscurity is a proven method of increasing the work factor that an adversary must expend to successfully attack a system. By itself, obscurity is not good protection, but it can complement other controls when both are properly employed.

Similar approaches are seen in computer and network security when attempting to hide certain objects. A network administrator may, for instance, move a service from its default port to a different port so that others will not know how to access it as easily, or a firewall may be configured to hide specific information about the internal network in the hope that potential attackers will not obtain the information for use in an attack on the network. In most security circles, security through obscurity is considered a poor

approach, especially if it is the only approach to security. Security through obscurity simply attempts to hide an object; it doesn’t implement a security control to protect it. An organization can use security through

obscurity measures to try to hide critical assets, but other security measures should also be employed to provide a higher level of protection. For example, if an administrator moves a service from its default port to a more obscure port, an attacker can still actually find this service; thus a firewall should be used to restrict access to the service. Most people know that even if you do shove your ice cream to the back of the freezer, someone may eventually find it.

Least Common Mechanism The principle of least common mechanism states that mechanisms used to access resources should be dedicated and not shared. Sharing of mechanisms allows a potential cross-over between channels resulting in a protection failure mode. For example, if there is a module that enables employees to check their payroll information, a separate module should be employed to change the information, lest a user gain access to change versus read access. Although sharing and reuse are good in one sense, they can represent a security risk in another. Common examples of the least common mechanism and its isolation

principle abound in ordinary systems. Sandboxing is a means of separating the operation of an application from the rest of the operating system. Virtual machines perform the same task between operating systems on a single piece of hardware. Instantiating shared libraries, in which separate instantiation of local classes enables separate but equal coding, is yet another. The key is to provide a means of isolation between processes so information cannot flow between separate users unless specifically designed to do so.

It often amazes security professionals how frequently individuals rely on security through obscurity as their main line of defense. Relying on some piece of information remaining secret is generally not a good idea. This is especially true in this age of reverse-engineering, where individuals analyze the binaries for programs to discover embedded passwords or cryptographic keys. The biggest problem with relying on security through obscurity is that if it fails and the

secret becomes known, there often is no easy way to modify the secret to re-secure it.

Psychological Acceptability Psychological acceptability refers to the users’ acceptance of security measures. Users play a key role in the operation of a system, and if security measures are perceived to be an impediment to the work a user is responsible for, then a natural consequence may be that the user bypasses the control. Although a user may understand that this could result in a security problem, the perception that it does result in their performance failure will present pressure to bypass it. Psychological acceptability is often overlooked by security

professionals focused on technical issues and how they see the threat. They are focused on the threat, which is their professional responsibility, so the focus on security is natural and it aligns with their professional responsibilities. This alignment between security and professional work responsibilities does not always translate to other positions in an organization. Security professionals, particularly those designing the security systems, should not only be aware of this concept, but pay particular attention to how security controls will be viewed by workers in the context of their work responsibility, not with respect to security for its own sake.

Defense in Depth Defense in depth is a principle that is characterized by the use of multiple, different defense mechanisms with a goal of improving the defensive response to an attack. Another term for defense in depth is layered security. Single points of failure represent just that, an opportunity to fail. By using multiple defenses that are different, with differing points of failure, a system becomes stronger. While one defense mechanism may not be 100 percent effective, the application of a second defense mechanism to the items that succeed in bypassing the first mechanism provides a stronger response. There are a couple of different mechanisms that can be

employed in a defense-in-depth strategy: layered security and diversity of defense. Together these provide a defense-in-depth strategy that is stronger than any single layer of defense. A bank does not protect the money that it stores only by using a vault. It

has one or more security guards as a first defense to watch for suspicious activities and to secure the facility when the bank is closed. It may have monitoring systems that watch various activities that take place in the bank, whether involving customers or employees. The vault is usually located in the center of the facility, and thus there are layers of rooms or walls before arriving at the vault. There is access control, which ensures that the people entering the vault have to be given authorization beforehand. And the systems, including manual switches, are connected directly to the police station in case a determined bank robber successfully penetrates any one of these layers of protection. Networks should utilize the same type of layered security architecture.

There is no 100 percent secure system, and there is nothing that is foolproof, so a single specific protection mechanism should never be solely relied upon. It is important that every environment have multiple layers of security. These layers may employ a variety of methods, such as routers, firewalls, network segments, IDSs, encryption, authentication software, physical security, and traffic control. The layers need to work together in a coordinated manner so that one does not impede another’s functionality and introduce a security hole. As an example, consider the steps an intruder might have to take to

access critical data held within a company’s back-end database. The intruder first has to penetrate the firewall and use packets and methods that will not be identified and detected by the IDS (more information on these devices can be found in Chapter 13). The attacker next has to circumvent an internal router performing packet filtering, and then possibly penetrate another firewall used to separate one internal network from another (see Figure 2.3). From there, the intruder must break the access controls that are on the database, which means having to do a dictionary or brute-force attack to be able to authenticate to the database software. Once the intruder

has gotten this far, the data still needs to be located within the database. This may in turn be complicated by the use of access control lists outlining who can actually view or modify the data. That is a lot of work.

• Figure 2.3 Layered security

This example illustrates the different layers of security many environments employ. It is important to implement several different layers because if intruders succeed at one layer, you want to be able to stop them at the next. The redundancy of different protection layers assures that there is no one single point of failure pertaining to security. If a network used only a firewall to protect its assets, an attacker able to penetrate this device successfully would find the rest of the network open and vulnerable. An example of how different security methods can work against each

other is exemplified when firewalls encounter encrypted network traffic. An organization may utilize encryption so that an outside customer communicating with a specific web server is assured that sensitive data being exchanged is protected. If this encrypted data is encapsulated within Secure Sockets Layer (SSL) or Transport Layer Security (TLS) packets and then sent through a firewall, the firewall may not be able to read the payload information in the individual packets. The layers usually are depicted starting at the top, with more general

types of protection, and progressing downward through each layer, with increasing granularity at each layer as you get closer to the actual resource, as you can see in Figure 2.4. This is because the top-layer protection mechanism is responsible for looking at an enormous amount of traffic, and it would be overwhelming and cause too much of a performance degradation if each aspect of the packet were inspected. Instead, each layer usually digs deeper into the packet and looks for specific items. Layers that are closer to the resource have to deal with only a fraction of the traffic that the top-layer security mechanism does, and thus looking deeper and at more granular aspects of the traffic will not cause as much of a performance hit.

• Figure 2.4 Various layers of security

Diversity of Defense Diversity of defense is a concept that complements the idea of various layers of security. It involves making different layers of security dissimilar so that even if attackers know how to get through a system that comprises one layer, they may not know how to get through a different type of layer that employs a different system for security. If an environment has two firewalls that form a demilitarized zone

(DMZ), for example, one firewall may be placed at the perimeter of the Internet and the DMZ. This firewall analyzes the traffic that is entering through that specific access point and enforces certain types of restrictions. The other firewall may then be placed between the DMZ and the internal network. When applying the diversity-of-defense concept, you should set up these two firewalls to filter for different types of traffic and provide

different types of restrictions. The first firewall, for example, may make sure that no FTP, SNMP, or Telnet traffic enters the network but allow SMTP, SSH, HTTP, and SSL traffic through. The second firewall may not allow SSL or SSH through and may interrogate SMTP and HTTP traffic to make sure that certain types of attacks are not part of that traffic.

Access Control The term access control has been used to describe a variety of protection schemes. It sometimes refers to all security features used to prevent unauthorized access to a computer system or network. In this sense, it may be confused with authentication. More properly, access control is the ability to control whether a subject (such as an individual or a process running on a computer system) can interact with an object (such as a file or hardware device). Authentication, on the other hand, deals with verifying the identity of a subject. To help understand the difference, consider the example of an individual attempting to log into a computer system or network. Authentication is the process used to verify to the computer system or network that the individual is who they claim to be. The most common method to do this is through the use of a user ID and password. Once the individual has verified their identity, access controls regulate what the individual can actually do on the system. Just because a person is granted entry to the system does not mean that they should have access to all data the system contains.

Authentication Mechanisms Access controls define what actions a user can perform or what objects a user can have access to. These controls assume that the identity of the user has been verified. It is the job of authentication mechanisms to ensure that only valid users are admitted. Described another way, authentication is using some mechanism to prove that you are who you claim to be. There are three general factors commonly used in authentication. In order to

verify your identity, you can provide

Something you know (knowledge factor)

Something you have (possession factor)

Something about you (something that you are; inherent factor)

The most common authentication mechanism is to provide something that only you, the valid user, should know. The most frequently used example of this is the common user ID (or username) and password. In theory, since you are not supposed to share your password with anybody else, only you should know your password, and thus by providing it, you are proving to the system that you are who you claim to be. Another mechanism for authentication is to provide something that you have in your possession, such as a magnetic stripe card that contains identifying information. The third mechanism is to use something about you for identification purposes, such as your fingerprint or the geometry of your hand. Obviously, for the second and third mechanisms to work, additional hardware devices need to be used (to read the card, fingerprint, or hand geometry).

Access Control vs. Authentication It may seem that access control and authentication are two ways to describe the same protection mechanism. This, however, is not the case. Authentication provides a way to verify to the computer who the user is. Once the user has been authenticated, the access controls decide what operations the user can perform. The two go hand-in-hand but they are not the same thing.

Authentication and Access Control Policies Policies are statements of what the organization wants to accomplish. The organization needs to identify goals and intentions for many different aspects of security. Each aspect will have associated policies and

procedures.

Group Policy Operating systems such as Windows and Linux allow administrators to organize users into groups, to create categories of users for which similar access policies can be established. Using groups saves the administrator time, as adding a new user will not require the administrator to create a completely new user profile; instead, the administrator can determine to which group the new user belongs and then add the user to that group. A group policy defines for the group things such as the applicable

operating system and application settings and permissions. Examples of groups commonly found include administrator, user, and guest. Take care when creating groups and assigning users to them so that you do not provide more access than is absolutely required for members of that group. It would be simple to make everybody an administrator—it would cut down on the number of requests users make of beleaguered administrators —but this is not a wise choice, as it also enables users to modify the system in ways that could impact security. Establishing the rights levels of access for the various groups up front will save you time and eliminate potential problems that might be encountered later on. More on this subject will be covered in Chapter 14.

Tech Tip

Group Policy The term group policy has different meanings in Linux and Windows systems. In Linux, group policies typically refer to group-level permissions associated with file systems. In Windows, group policies refer to Active Directory objects used to enforce configuration and permissions across a domain.

Password Policy

Since passwords are the most common authentication mechanism, it is imperative that organizations have a policy that addresses them. The password policy should address the procedures used for selecting user passwords (specifying what is considered an acceptably complex password in the organization in terms of the character set and length), the frequency with which passwords must be changed, and how passwords will be distributed. Procedures for creating new passwords should an employee forget her old password also need to be addressed, as well as the acceptable handling of passwords (for example, they should not be shared with anybody else, they should not be written down, and so on). It might also be useful to have the policy address the issue of password cracking by administrators, to enable them to discover weak passwords selected by employees.

A password policy is one of the most basic policies that an organization can have. Make sure you understand the basics of what constitutes a good password along with the other issues that surround password creation, expiration, sharing, and use.

Note that the developer of the password policy and associated procedures can go overboard and create an environment that negatively impacts employee productivity and leads to poorer security, not better. If, for example, the frequency with which passwords are changed is too great, users might write them down or forget them. Neither of these is a desirable outcome, as the former makes it possible for an intruder to find a password and gain access to the system, and the latter leads to too many people losing productivity as they wait for a new password to be created to allow them access again. More information on password policies can be found in Chapter 22.

Security Models

An important issue when designing the software that will operate and control secure computer systems and networks is the security model that the system or network will be based upon. The security model will implement the security policy that has been chosen and enforce those characteristics deemed most important by the system designers. For example, if confidentiality is considered paramount, the model should make certain no data is disclosed to unauthorized individuals. A model enforcing confidentiality may allow unauthorized individuals to modify or delete data, as this would not violate the tenets of the model because the true values for the data would still remain confidential. Of course, this model may not be appropriate for all environments. In some instances, the unauthorized modification of data may be considered a more serious issue than its unauthorized disclosure. In such cases, the model would be responsible for enforcing the integrity of the data instead of its confidentiality. Choosing the model to base the design on is critical if you want to ensure that the resulting system accurately enforces the security policy desired. This, however, is only the starting point, and it does not imply that you have to make a choice between confidentiality and data integrity, as both are important.

Confidentiality Models Data confidentiality has generally been the chief concern of the military. For instance, the U.S. military encouraged the development of the Bell- LaPadula security model to address data confidentiality in computer operating systems. This model is especially useful in designing multilevel security systems that implement the military’s hierarchical security scheme, which includes levels of classification such as Unclassified, Confidential, Secret, and Top Secret. Similar classification schemes can be used in industry, where classifications might include Publicly Releasable, Proprietary, and Company Confidential. A second confidentiality model, the Brewer-Nash security model, is

one defined by controlling read and write access based on conflict of

interest rules. This model is also known as the Chinese Wall model, after the concept of separating groups through the use of an impenetrable wall.

Bell-LaPadula Model The Bell-LaPadula security model employs both mandatory and discretionary access control mechanisms when implementing its two basic security principles. The first of these principles is called the Simple Security Rule, which states that no subject (such as a user or a program) can read information from an object (such as a file) with a security classification higher than that possessed by the subject itself. This means that the system must prevent a user with only a Secret clearance, for example, from reading a document labeled Top Secret. This rule is often referred to as the “no-read-up” rule.

The Simple Security Rule is just that: the most basic of security rules. It essentially states that in order for you to see something, you have to be authorized to see it.

The second security principle enforced by the Bell-LaPadula security model is known as the *-property (pronounced “star property”). This principle states that a subject can write to an object only if the target’s security classification is greater than or equal to the object’s security classification. This means that a user with a Secret clearance can write to a file with a Secret or Top Secret classification but cannot write to a file with only an Unclassified classification. This at first may appear to be a bit confusing, since this principle allows users to write to files that they are not allowed to view, thus enabling them to actually destroy files that they don’t have the classification to see. This is true, but keep in mind that the Bell-LaPadula model is designed to enforce confidentiality, not integrity. Writing to a file that you don’t have the clearance to view is not considered a confidentiality issue; it is an integrity issue. Whereas the *-property allows a user to write to a file of equal or

greater security classification, it doesn’t allow a user to write to a file with a lower security classification. This, too, may be confusing at first—after all, shouldn’t a user with a Secret clearance, who can view a file marked Unclassified, be allowed to write to that file? The answer to this, from a security perspective, is “no.” The reason again relates to wanting to avoid either accidental or deliberate security disclosures. The system is designed to make it impossible (hopefully) for data to be disclosed to those without the appropriate level to view it. As shown in Figure 2.5, if it were possible for a user with a Top Secret clearance to either deliberately or accidentally write Top Secret information and place it in a file marked Confidential, a user with only a Confidential security clearance could then access this file and view the Top Secret information. Thus, data would have been disclosed to an individual not authorized to view it. This is what the system should protect against and is the reason for what is known as the “no-write-down” rule.

• Figure 2.5 Bell-LaPadula security model

Not all environments are more concerned with confidentiality than integrity. In a financial institution, for example, viewing somebody’s bank balance is an issue, but a greater issue would be the ability to actually modify that balance. In environments where integrity is more important, a different model than the Bell-LaPadula security model is needed.

Brewer-Nash Security Model One of the tenets associated with access is need to know. Separate groups within an organization may have differing needs with respect to access to information. A security model that takes into account user conflict-of- interest aspects is the Brewer-Nash security model. In this model, information flows are modeled to prevent information from flowing between subjects and objects when a conflict of interest would occur. As previously noted, this model is also known as a Chinese Wall model, after the Great Wall of China, a structure designed to separate groups of people. As shown in Figure 2.6, separate groups are defined and access controls are designed to enforce the separation of the groups.

• Figure 2.6 Brewer-Nash security model

Integrity Models

The Bell-LaPadula model was developed in the early 1970s but was found to be insufficient for all environments. As an alternative, Kenneth Biba studied the integrity issue and developed what is called the Biba security model in the late 1970s. Additional work was performed in the 1980s that led to the Clark-Wilson security model, which also places its emphasis on integrity rather than confidentiality.

The Biba Security Model In the Biba model (see Figure 2.7), instead of security classifications, integrity levels are used. A principle of integrity levels is that data with a higher integrity level is believed to be more accurate or reliable than data with a lower integrity level. Integrity levels indicate the level of “trust” that can be placed in information at the different levels. Integrity levels differ from security levels in another way—they limit the modification of information as opposed to the flow of information.

• Figure 2.7 Bibb Security Model

An initial attempt at implementing an integrity-based model was captured in what is referred to as the Low-Water-Mark policy. This policy in many ways is the opposite of the *-property in that it prevents subjects from writing to objects of a higher integrity level. The policy also contains a second rule that states the integrity level of a subject will be lowered if it reads an object of a lower integrity level. The reason for this is that if the subject then uses data from that object, the highest the integrity level can be for a new object created from it is the same level of integrity of the original object. In other words, the level of trust you can

place in data formed from data at a specific integrity level cannot be higher than the level of trust you have in the subject creating the new data object, and the level of trust you have in the subject can only be as high as the level of trust you had in the original data. The final rule contained in the Low-Water-Mark policy states that a subject can execute a program only if the program’s integrity level is equal to or less than the integrity level of the subject. This ensures that data modified by a program only has the level of trust (integrity level) that can be placed in the individual who executed the program. While the Low-Water-Mark policy certainly prevents unauthorized

modification of data, it has the unfortunate side effect of eventually lowering the integrity levels of all subjects to the lowest level on the system (unless the subject always views files with the same level of integrity). This is because of the second rule, which lowers the integrity level of the subject after accessing an object of a lower integrity level. There is no way specified in the policy to ever raise the subject’s integrity level back to its original value. A second policy, known as the Ring policy, addresses this issue by allowing any subject to read any object without regard to the object’s level of integrity and without lowering the subject’s integrity level. This, unfortunately, can lead to a situation where data created by a subject after reading data of a lower integrity level could end up having a higher level of trust placed upon it than it should. The Biba security model implements a hybrid of the Ring and Low-

Water-Mark policies. Biba’s model in many respects is the opposite of the Bell-LaPadula model in that what it enforces are “no-read-down” and “no- write-up” policies. It also implements a third rule that prevents subjects from executing programs of a higher level. The Biba security model thus addresses the problems mentioned with both the Ring and Low-Water- Mark policies.

The Clark-Wilson Security Model The Clark-Wilson security model takes an entirely different approach than the Biba and Bell-LaPadula models, using transactions as the basis for

its rules. It defines two levels of integrity only: constrained data items (CDIs) and unconstrained data items (UDIs). CDI data is subject to integrity controls while UDI data is not. The model then defines two types of processes: integrity verification processes (IVPs), which ensure that CDI data meets integrity constraints (to ensure the system is in a valid state), and transformation processes (TPs), which change the state of data from one valid state to another. Data in this model cannot be modified directly by a user; it must be changed by trusted TPs, access to which can be restricted (thus restricting the ability of a user to perform certain activities). It is useful to return to the prior example of the banking account balance

to describe the need for integrity-based models. In the Clark-Wilson model, the account balance would be a CDI because its integrity is a critical function for the bank. A client’s color preference for their checkbook is not a critical function and would be considered a UDI. Since the integrity of account balances is of extreme importance, changes to a person’s balance must be accomplished through the use of a TP. Ensuring that the balance is correct would be the duty of an IVP. Only certain employees of the bank should have the ability to modify an individual’s account, which can be controlled by limiting the number of individuals who have the authority to execute TPs that result in account modification. Certain very critical functions may actually be split into multiple TPs to enforce another important principle, separation of duties (introduced earlier in the chapter). This limits the authority any one individual has so that multiple individuals will be required to execute certain critical functions.

Chapter 2 Review

Chapter Summary

After reading this chapter and completing the exercises, you should understand the following regarding the basics of security, security terminology, and security models.

Define basic terms associated with computer and information security

Information assurance and information security place the security focus on the information and not on the hardware or software used to process it.

The original goal of computer and network security was to provide confidentiality, integrity, and availability—the “CIA” of security.

Additional elements of security can include authentication, authorization, auditability, and nonrepudiation.

The operational model of computer security tells us that protection is provided by prevention, detection, and response.

Identify the basic approaches to computer and information security

Host security focuses on protecting each computer and device individually, whereas network security focuses on addressing protection of the network as a whole.

For many organizations, a combination of host security and network security is needed to adequately address the wide range of possible security threats.

Identify the basic principles of computer and information security

Principle of least privilege is to use the minimum privileges necessary to perform a task.

Principle of separation of privilege states that critical items should require multiple parties.

Principle of fail-safe default states that deny by default (implicit deny) and only grant access with explicit permission should be employed in

access decisions.

Principle of economy of mechanism states that protection mechanisms should be small and simple.

Principle of complete mediation states that protection mechanisms should cover every access to every object and should never be bypassed.

Principle of open design states that protection mechanisms should not depend upon secrecy of the mechanism itself.

Principle of least common mechanism states that the protection mechanisms should be shared to the least degree possible among users.

Principle of psychological acceptability states that protection mechanisms should not impact users, or if they do, the impact should be minimal.

Principle of defense in depth, or layered security, is that multiple layers of differing, overlapping controls should be employed.

Diversity of defense is a concept that complements the idea of various layers of security. It means to make the layers dissimilar so that if one layer is penetrated, the next layer can’t also be penetrated using the same method.

Distinguish among various methods to implement access controls

Access is the ability of a subject to interact with an object. Access controls are those devices and methods used to limit which subjects may interact with specific objects.

An access control list (ACL) is a mechanism that is used to define whether a user has certain access privileges for a system. Other methods include discretionary access control (DAC), mandatory access control (MAC), role-based access control (RBAC), and rule-based access control.

Describe methods used to verify the identity and authenticity of an individual

Authentication mechanisms ensure that only valid users are provided access to the computer system or network.

The three general methods commonly used in authentication involve users providing either something they know, something they have, or something unique about them (something they are).

Recognize some of the basic models used to implement security in operating systems

Security models enforce the chosen security policy.

There are two basic categories of models: those that ensure confidentiality and those that ensure integrity.

Bell-LaPadula is a confidentiality security model whose development was prompted by the demands of the U.S. military and its security clearance scheme.

The Bell-LaPadula security model enforces “no-read-up” and “no- write-down” rules to avoid the deliberate or accidental disclosure of information to individuals not authorized to receive it.

The Brewer-Nash security model (Chinese Wall model) is a confidentiality model that separates users based on conflicts of interest.

The Biba security model is an integrity-based model that, in many respects, implements the opposite of what the Bell-LaPadula model does—that is, “no-read-down” and “no-write-up” rules.

The Clark-Wilson security model is an integrity-based model designed to limit the processes an individual may perform as well as require that critical data be modified only through specific transformation processes.

Key Terms *-property (34) access control (31) auditability (20) authentication (20) availability (20) Bell-LaPadula security model (34) Biba security model (35) Brewer-Nash security model (34) Clark-Wilson security model (37) complete mediation (27) confidentiality (20) default deny (26) defense in depth (29) diversity of defense (31) economy of mechanism (27) fail-safe defaults (26) hacking (19) host security (23) implicit deny (26) integrity (20) layered security (29) least common mechanism (28) least privilege (24) Low-Water-Mark policy (36) network security (24) nonrepudiation (20) open design (27) operational model of computer security (20) phreaking (19)

psychological acceptability (29) Ring policy (36) security through obscurity (28) separation of duties (25) separation of privilege (25) Simple Security Rule (34)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. _______________ is a term used to describe the condition where a user cannot deny that an event has occurred.

2. The _______________ is an integrity-based security model that bases its security on control of the processes that are allowed to modify critical data, referred to as constrained data items.

3. The security principle used in the Bell-LaPadula security model that states that no subject can read from an object with a higher security classification is called the _______________.

4. The principle that states a subject has only the necessary rights and privileges to perform its task, with no additional permissions, is called _______________.

5. _______________ is the principle in security where protection mechanisms should be kept as simple and as small as possible.

6. _______________ is the principle that protection mechanisms should minimize user-level impact.

7. _______________ is the process used to ensure that an individual is who they claim to be.

8. The architecture in which multiple methods of security defense are

applied to prevent realization of threat-based risks is called _______________.

9. _______________ is the process of combining seemingly unimportant information with other pieces of information to divulge potentially sensitive information.

10. Implicit deny is an operationalization of the principle of _______________.

Multiple-Choice Quiz 1. Which of the following is not a principle of security?

A. Principle of least privilege

B. Principle of economy of mechanism

C. Principle of efficient access

D. Principle of open access

2. The CIA of security includes: A. Confidentiality, integrity, authentication

B. Confidentiality, integrity, availability

C. Certificates, integrity, availability

D. Confidentiality, inspection, authentication

3. The security principle used in the Bell-LaPadula security model that states that no subject can read from an object with a higher security classification is the:

A. Simple Security Rule

B. Ring policy

C. Mandatory access control

D. *-property

4. Which of the following concepts requires users and system processes to use the minimal amount of permission necessary to function?

A. Layer defense

B. Diversified defense

C. Simple Security Rule

D. Least privilege

5. Which security model separates users based on conflict-of-interest issues?

A. Bell-LaPadula

B. Brewer-Nash

C. Biba

D. Clark-Wilson

6. The Bell-LaPadula security model is an example of a security model that is based on:

A. The integrity of the data

B. The availability of the data

C. The confidentiality of the data

D. The authenticity of the data

7. The term used to describe the requirement that different portions of a critical process must be performed by different people is:

A. Least privilege

B. Defense in depth

C. Separation of duties

D. Job rotation

8. Hiding information to prevent disclosure is an example of: A. Security through obscurity

B. Certificate-based security

C. Discretionary data security

D. Defense in depth

9. The problem with the Low-Water-Mark policy is that it: A. Is aimed at ensuring confidentiality and not integrity

B. Could ultimately result in all subjects having the integrity level of the least-trusted object on the system

C. Could result in the unauthorized modification of data

D. Does not adequately prevent users from viewing files they are not entitled to view

10. The concept of blocking an action unless it is specifically authorized is:

A. Implicit deny

B. Least privilege

C. Simple Security Rule

D. Hierarchical defense model

Essay Quiz 1. Your company has decided to increase the authentication security

by requiring remote employees to use a security token as well as a

password to log onto the network. The employees are grumbling about the new requirements because they don’t want to have to carry around the token with them and don’t understand why it’s necessary. Write a brief memo to the staff to educate them on the general ways that authentication can be performed. Then explain why your company has decided to use security tokens in addition to passwords.

2. The new CEO for your company just retired from the military and wants to use some of the same computer systems and security software she used while with the military. Explain to her the reasons that confidentiality-based security models are not adequate for all environments. Provide at least two examples of environments where a confidentiality-based security model is not sufficient.

3. Describe why the concept of “security through obscurity” is generally considered a bad principle to rely on. Provide some real- world examples of where you have seen this principle used.

4. Write a brief essay describing the principle of least privilege and how it can be employed to enhance security. Provide at least two examples of environments in which it can be used for security purposes.

Lab Projects

• Lab Project 2.1 In an environment familiar to you (your school or where you work, for example), determine whether the principle of diversity of defense has been employed and list the different layers of security that are employed. Discuss whether you think they are sufficient and whether the principle of diversity of defense has also been used.

• Lab Project 2.2

Pick an operating system that enforces some form of access control and determine how it is implemented in that system.

chapter 3 Operational and Organizational Security

We will bankrupt ourselves in the vain search for absolute security.

—DWIGHT DAVID EISENHOWER

O

In this chapter, you will learn how to

Identify various operational aspects to security in your organization

Identify various policies and procedures in your organization

Identify the security awareness and training needs of an organization

Understand the different types of agreements employed in negotiating security requirements

Describe the physical security components that can protect your computers and network

Identify environmental factors that can affect security

Identify factors that affect the security of the growing number of wireless technologies used for data transmission

Prevent disclosure through electronic emanations

rganizations achieve operational security through policies and procedures that guide user’s interactions with data and data processing systems. Developing and aligning these efforts with the goals of the

business is a crucial part of developing a successful security program. One method of ensuring coverage is to align efforts with the operational security model described in the last chapter. This breaks efforts into groups; prevention, detection, and response elements. Prevention technologies are designed to keep individuals from being

able to gain access to systems or data they are not authorized to use. Originally, this was the sole approach to security. Eventually we learned that in an operational environment, prevention is extremely difficult and relying on prevention technologies alone is not sufficient. This led to the rise of technologies to detect and respond to events that occur when prevention fails. Together, the prevention technologies and the detection and response technologies form the operational model for computer security.

Policies, Procedures, Standards, and Guidelines An important part of any organization’s approach to implementing security are the policies, procedures, standards, and guidelines that are established to detail what users and administrators should be doing to maintain the security of the systems and network. Collectively, these documents provide the guidance needed to determine how security will be implemented in the organization. Given this guidance, the specific technology and security mechanisms required can be planned for. Policies are high-level, broad statements of what the organization wants

to accomplish. They are made by management when laying out the organization’s position on some issue. Procedures are the step-by-step instructions on how to implement policies in the organization. They describe exactly how employees are expected to act in a given situation or to accomplish a specific task. Standards are mandatory elements regarding the implementation of a policy. They are accepted specifications that provide specific details on how a policy is to be enforced. Some standards are externally driven. Regulations for banking and financial institutions, for example, require certain security measures be taken by law. Other standards may be set by the organization to meet its own security goals. Guidelines are recommendations relating to a policy. The key term in this case is recommendations—guidelines are not mandatory steps.

These documents guide how security will be implemented in the organization: Policies High-level, broad statements of what the organization wants to accomplish Procedures Step-by-step instructions on how to implement the policies Standards Mandatory elements regarding the implementation of a policy Guidelines Recommendations relating to a policy

Just as the network itself constantly changes, the policies, procedures, standards, and guidelines should be included in living documents that are

periodically evaluated and changed as necessary. The constant monitoring of the network and the periodic review of the relevant documents are part of the process that is the operational model. When applied to policies, this process results in what is known as the policy lifecycle. This operational process and policy lifecycle roughly consist of four steps in relation to your security policies and solutions:

1. Plan (adjust) for security in your organization. 2. Implement the plans. 3. Monitor the implementation. 4. Evaluate the effectiveness.

In the first step, you develop the policies, procedures, and guidelines that will be implemented and design the security components that will protect your network. There are a variety of governing instruments, from standards to compliance rules that will provide boundaries for these documents. Once these documents are designed and developed, you can implement the plans. Part of the implementation of any policy, procedure, or guideline is an instruction period during which those who will be affected by the change or introduction of this new document learn about its contents. Next, you monitor to ensure that both the hardware and the software as well as the policies, procedures, and guidelines are effective in securing your systems. Finally, you evaluate the effectiveness of the security measures you have in place. This step may include a vulnerability assessment (an attempt to identify and prioritize the list of vulnerabilities within a system or network) and a penetration test (a method to check the security of a system by simulating an attack by a malicious individual) of your system to ensure the security is adequate. After evaluating your security posture, you begin again with step one, this time adjusting the security mechanisms you have in place, and then continue with this cyclical process. Regarding security, every organization should have several common

policies in place (in addition to those already discussed relative to access control methods). These include, but are not limited to, security policies regarding change management, classification of information, acceptable use, due care and due diligence, due process, need to know, disposal and destruction of data, service level agreements, human resources issues, codes of ethics, and policies governing incident response.

Security Policies In keeping with the high-level nature of policies, the security policy is a high-level statement produced by senior management that outlines both what security means to the organization and the organization’s goals for security. The main security policy can then be broken down into additional policies that cover specific topics. Statements such as “this organization will exercise the principle of least access in its handling of client information” would be an example of a security policy. The security policy can also describe how security is to be handled from an organizational point of view (such as describing which office and corporate officer or manager oversees the organization’s security program). In addition to policies related to access control, the organization’s

security policy should include the specific policies described in the next sections. All policies should be reviewed on a regular basis and updated as needed. Generally, policies should be updated less frequently than the procedures that implement them, since the high-level goals will not change as often as the environment in which they must be implemented. All policies should be reviewed by the organization’s legal counsel, and a plan should be outlined that describes how the organization will ensure that employees will be made aware of the policies. Policies can also be made stronger by including references to the authority who made the policy (whether this policy comes from the CEO or is a department-level policy, for example) and references to any laws or regulations that are applicable to the specific policy and environment.

Change Management Policy The purpose of change management is to ensure proper procedures are followed when modifications to the IT infrastructure are made. These modifications can be prompted by a number of different events, including new legislation, updated versions of software or hardware, implementation of new software or hardware, or improvements to the infrastructure. The term “management” implies that this process should be controlled in some systematic way, and that is indeed the purpose. Changes to the infrastructure might have a detrimental impact on operations. New versions of operating systems or application software might be incompatible with other software or hardware the organization is using. Without a process to manage the change, an organization might suddenly find itself unable to conduct business. A change management process should include various stages, including a method to request a change to the infrastructure, a review and approval process for the request, an examination of the consequences of the change, resolution (or mitigation) of any detrimental effects the change might incur, implementation of the change, and documentation of the process as it related to the change.

Data Policies System integration with third parties frequently involves the sharing of data. Data can be shared for the purpose of processing or storage. Control over data is a significant issue in third-party relationships. There are numerous questions that need to be addressed. The question of who owns the data, both the data shared with third parties and subsequent data developed as part of the relationship, is an issue that needs to be established.

Data Ownership Data requires a data owner. Data ownership roles for all data elements need to be defined in the business. Data ownership is a business function,

where the requirements for security, privacy, retention, and other business functions must be established. Not all data requires the same handling restrictions, but all data requires these characteristics to be defined. This is the responsibility of the data owner.

Unauthorized Data Sharing Unauthorized data sharing can be a significant issue, and in today’s world, data has value and is frequently used for secondary purposes. Ensuring that all parties in the relationship understand the data-sharing requirements is an important prerequisite. Equally important is ensuring that all parties understand the security requirements of shared data.

Data Backups Data ownership requirements include backup responsibilities. Data backup requirements include determining the level of backup, restore objectives, and level of protection requirements. These can be defined by the data owner and then executed by operational IT personnel. Determining the backup responsibilities and developing the necessary operational procedures to ensure that adequate backups occur are important security elements.

Classification of Information A key component of IT security is the protection of the information processed and stored on the computer systems and network. Organizations deal with many different types of information, and they need to recognize that not all information is of equal importance or sensitivity. This requires classification of information into various categories, each with its own requirements for its handling. Factors that affect the classification of specific information include its value to the organization (what will be the impact to the organization if it loses this information?), its age, and laws or regulations that govern its protection. The most widely known system of classification of information is that implemented by the U.S. government

(including the military), which classifies information into categories such as Confidential, Secret, and Top Secret. Businesses have similar desires to protect information and often use categories such as Publicly Releasable, Proprietary, Company Confidential, and For Internal Use Only. Each policy for the classification of information should describe how it should be protected, who may have access to it, who has the authority to release it and how, and how it should be destroyed. All employees of the organization should be trained in the procedures for handling the information that they are authorized to access. Discretionary and mandatory access control techniques use classifications as a method to identify who may have access to what resources.

Tech Tip

Data Classification Information classification categories you should be aware of for the CompTIA Security+ exam include: High, Medium, Low, Confidential, Private, and Public.

Data Labeling, Handling, and Disposal Effective data classification programs include data labeling, which enables personnel working with the data to know whether it is sensitive and to understand the levels of protection required. When the data is inside an information-processing system, the protections should be designed into the system. But when the data leaves this cocoon of protection, whether by printing, downloading, or copying, it becomes necessary to ensure continued protection by other means. This is where data labeling assists users in fulfilling their responsibilities. Training to ensure that labeling occurs and that it is used and followed is important for users whose roles can be impacted by this material. Training plays an important role in ensuring proper data handling and

disposal. Personnel are intimately involved in several specific tasks

associated with data handling and data destruction/disposal and, if properly trained, can act as a security control. Untrained or inadequately trained personnel will not be a productive security control and, in fact, can be a source of potential compromise.

Need to Know Another common security principle is that of need to know, which goes hand-in-hand with least privilege. The guiding factor here is that each individual in the organization is supplied with only the absolute minimum amount of information and privileges he or she needs to perform their work tasks. To obtain access to any piece of information, the individual must have a justified need to know. A policy spelling out these two principles as guiding philosophies for the organization should be created. The policy should also address who in the organization can grant access to information and who can assign privileges to employees.

Disposal and Destruction Policy Many potential intruders have learned the value of dumpster diving. An organization must be concerned about not only paper trash and discarded objects, but also the information stored on discarded objects such as computers. Several government organizations have been embarrassed when old computers sold to salvagers proved to contain sensitive documents on their hard drives. It is critical for every organization to have a strong disposal and destruction policy and related procedures. Important papers should be shredded, and important in this case means

anything that might be useful to a potential intruder. It is amazing what intruders can do with what appear to be innocent pieces of information. Before magnetic storage media (such as disks or tapes) is discarded in

the trash or sold for salvage, it should have all files deleted, and should be overwritten at least three times with all 1’s, all 0’s, and then random characters. Commercial products are available to destroy files using this process. It is not sufficient simply to delete all files and leave it at that,

since the deletion process affects only the pointers to where the files are stored and doesn’t actually get rid of all the bits in the file. This is why it is possible to “undelete” files and recover them after they have been deleted. A safer method for destroying files from a storage device is to destroy

the data magnetically, using a strong magnetic field to degauss the media. This effectively destroys all data on the media. Several commercial degaussers are available for this purpose. Another method that can be used on hard drives is to use a file on them (the sort of file you’d find in a hardware store) and actually file off the magnetic material from the surface of the platter. Shredding floppy media is normally sufficient, but simply cutting a floppy disk into a few pieces is not enough—data has been successfully recovered from floppies that were cut into only a couple of pieces. CDs and DVDs also need to be disposed of appropriately. Many paper shredders now have the ability to shred these forms of storage media. In some highly secure environments, the only acceptable method of disposing of hard drives and other storage devices is the actual physical destruction of the devices. Matching the security action to the level of risk is important to recognize in this instance. Destroying hard drives that do not have sensitive information is wasteful; proper file scrubbing is probably appropriate. For drives with ultra-sensitive information, physical destruction makes sense. There is no single answer, but as in most things associated with information security, the best practice is to match the action to the level of risk.

Human Resources Policies It has been said that the weakest links in the security chain are the humans. Consequently, it is important for organizations to have policies in place relative to their employees. Policies that relate to the hiring of individuals are primarily important. The organization needs to make sure that it hires individuals who can be trusted with the organization’s data and that of its clients. Once employees are hired, they should be kept from slipping into the category of “disgruntled employee.” Finally, policies must be

developed to address the inevitable point in the future when an employee leaves the organization—either on his or her own or with the “encouragement” of the organization itself. Security issues must be considered at each of these points.

Many organizations overlook the security implications that decisions by Human Resources may have. Human Resources personnel and security personnel should have a close working relationship. Decisions on the hiring and firing of personnel have direct security implications for the organization. As a result, procedures should be in place that specify which actions must be taken when an employee is hired, is terminated, or retires.

Code of Ethics Numerous professional organizations have established codes of ethics for their members. Each of these describes the expected behavior of their members from a high-level standpoint. Organizations can adopt this idea as well. For organizations, a code of ethics can set the tone for how employees will be expected to act and to conduct business. The code should demand honesty from employees and require that they perform all activities in a professional manner. The code could also address principles of privacy and confidentiality and state how employees should treat client and organizational data. Conflicts of interest can often cause problems, so this could also be covered in the code of ethics. By outlining a code of ethics, the organization can encourage an

environment that is conducive to integrity and high ethical standards. For additional ideas on possible codes of ethics, check professional organizations such as the Institute for Electrical and Electronics Engineers (IEEE), the Association for Computing Machinery (ACM), or the Information Systems Security Association (ISSA).

Tech Tip

Hiring Hackers Hiring a skilled hacker may make sense from a technical skills point of view, but an organization also has to consider the broader ethical and business consequences and associated risks. Is the hacker completely reformed or not? How much time is needed to determine this? The real question is not “Would you hire a hacker?” but rather “Can you fire a hacker once he has had access to your systems?” Trust is an important issue with employees who have system administrator access, and the long-term ramifications need to be considered.

Job Rotation An interesting approach to enhance security that is gaining increasing attention is job rotation. Organizations often discuss the benefits of rotating individuals through various jobs in an organization’s IT department. By rotating through jobs, individuals gain a better perspective on how the various parts of IT can enhance (or hinder) the business. Since security is often a misunderstood aspect of IT, rotating individuals through security positions can result in a much wider understanding throughout the organization about potential security problems. It also can have the side benefit of a company not having to rely on any one individual too heavily for security expertise. If all security tasks are the domain of one employee, and that individual leaves suddenly, security at the organization could suffer. On the other hand, if security tasks are understood by many different individuals, the loss of any one individual has less of an impact on the organization.

Employee Hiring and Promotions It is becoming common for organizations to run background checks on prospective employees and to check the references prospective employees supply. Frequently, organizations require drug testing, check for any past criminal activity, verify claimed educational credentials, and confirm reported work history. For highly sensitive environments, special security background investigations can also be required. Make sure that your organization hires the most capable and trustworthy employees, and that your policies are designed to ensure this.

After an individual has been hired, your organization needs to minimize the risk that the employee will ignore company rules and affect security. Periodic reviews by supervisory personnel, additional drug checks, and monitoring of activity during work may all be considered by the organization. If the organization chooses to implement any of these reviews, this must be specified in the organization’s policies, and prospective employees should be made aware of these policies before being hired. What an organization can do in terms of monitoring and requiring drug tests, for example, can be severely restricted if not spelled out in advance as terms of employment. New hires should be made aware of all pertinent policies, especially those applying to security, and should be asked to sign documents indicating that they have read and understood them.

Tech Tip

Accounts of Former Employees When conducting security assessments of organizations, security professionals frequently find active accounts for individuals who no longer work for the company. This is especially true for larger organizations, which may lack a clear process for the personnel office to communicate with the network administrators when an employee leaves the organization. These old accounts, however, are a weak point in the security perimeter for the organization and should be eliminated.

Occasionally an employee’s status will change within the company. If the change can be construed as a negative personnel action (such as a demotion), supervisors should be alerted to watch for changes in behavior that might indicate the employee is contemplating or conducting unauthorized activity. It is likely that the employee will be upset, and whether he acts on this to the detriment of the company is something that needs to be guarded against. In the case of a demotion, the individual may also lose certain privileges or access rights, and these changes should be made quickly so as to lessen the likelihood that the employee will destroy

previously accessible data if he becomes disgruntled and decides to take revenge on the organization. On the other hand, if the employee is promoted, privileges may still change, but the need to make the change to access privileges may not be as urgent, though it should still be accomplished as quickly as possible. If the move is a lateral one, changes may also need to take place, and again they should be accomplished as quickly as possible.

Retirement, Separation, or Termination of an Employee An employee leaving an organization can be either a positive or a negative action. Employees who are retiring by their own choice may announce their planned retirement weeks or even months in advance. Limiting their access to sensitive documents the moment they announce their intention may be the safest thing to do, but it might not be necessary. Each situation should be evaluated individually. If the situation is a forced retirement, the organization must determine the risk to its data if the employee becomes disgruntled as a result of the action. In this situation, the wisest choice might be to cut off the employee’s access quickly and provide her with some additional vacation time. This might seem like an expensive proposition, but the danger to the company of having a disgruntled employee may justify it. Again, each case should be evaluated individually.

It is better to give a potentially disgruntled employee several weeks of paid vacation than to have him trash sensitive files to which he has access. Because employees typically know the pattern of management behavior with respect to termination, doing the right thing will pay dividends in the future for a firm.

When an employee decides to leave a company, generally as a result of a new job offer, continued access to sensitive information should be carefully considered. If the employee is leaving as a result of hard feelings toward the company, it might be wise to quickly revoke her access

privileges. If the employee is leaving the organization because he is being

terminated, you should assume that he is or will become disgruntled. While it may not seem the friendliest thing to do, an employee in this situation should immediately have his access privileges to sensitive information and facilities revoked. Combinations should also be quickly changed once an employee has

been informed of their termination. Access cards, keys, and badges should be collected; the employee should be escorted to her desk and watched as she packs personal belongings; and then she should be escorted from the building.

Organizations commonly neglect to have a policy that mandates the removal of an individual’s computer access upon termination. Not only should such a policy exist, but it should also include the procedures to reclaim and “clean” a terminated employee’s computer system and accounts.

Mandatory Vacations Organizations have provided vacation time to their employees for many years. Few, however, force employees to take this time if they don’t want to. At some companies, employees are given the choice to either “use or lose” their vacation time; if they do not take all of their vacation time, they lose at least a portion of it. From a security standpoint, an employee who never takes time off might be involved in nefarious activity, such as fraud or embezzlement, and might be afraid that if he leaves on vacation, the organization will discover his illicit activities. As a result, requiring employees to use their vacation time through a policy of mandatory vacations can be a security protection mechanism. Using mandatory vacations as a tool to detect fraud will require that somebody else also be trained in the functions of the employee who is on vacation. Having a second person familiar with security procedures is also a good policy in

case something happens to the primary employee.

On-boarding/Off-boarding Business Partners Just as it is important to manage the on- and off-boarding processes of company personnel, it is important to consider the same types of elements when making arrangements with third parties. Agreements with business partners tend to be fairly specific with respect to terms associated with mutual expectations associated with the process of the business. Considerations regarding the on-boarding and off-boarding processes are important, especially the off-boarding. When a contract arrangement with a third party comes to an end, issues as to data retention and destruction by the third party need to be addressed. These considerations need to be made prior to the establishment of the relationship, not added at the time that it is coming to an end.

On-boarding and off-boarding business procedures should be well documented to ensure compliance with legal requirements.

Social Media Networks The rise of social media networks has changed many aspects of business. Whether used for marketing, communications, customer relations, or some other purpose, social media networks can be considered a form of third party. One of the challenges in working with social media networks and/or applications is their terms of use. While a relationship with a typical third party involves a negotiated set of agreements with respect to requirements, there is no negotiation with social media networks. The only option is to adopt their terms of service, so it is important to understand the implications of these terms with respect to the business use of the social network.

Acceptable Use Policy An acceptable use policy (AUP) outlines what the organization considers to be the appropriate use of company resources, such as computer systems, e-mail, Internet access, and networks. Organizations should be concerned about personal use of organizational assets that does not benefit the company. The goal of the AUP is to ensure employee productivity while limiting

organizational liability through inappropriate use of the organization’s assets. The AUP should clearly delineate what activities are not allowed. It should address issues such as the use of resources to conduct personal business, installation of hardware or software, remote access to systems and networks, the copying of company-owned software, and the responsibility of users to protect company assets, including data, software, and hardware. Statements regarding possible penalties for ignoring any of the policies (such as termination) should also be included. Related to appropriate use of the organization’s computer systems and

networks by employees is the appropriate use by the organization. The most important of such issues is whether the organization considers it appropriate to monitor the employees’ use of the systems and network. If monitoring is considered appropriate, the organization should include a statement to this effect in the banner that appears at login. This repeatedly warns employees, and possible intruders, that their actions are subject to monitoring and that any misuse of the system will not be tolerated. Should the organization need to use in a civil or criminal case any information gathered during monitoring, the issue of whether the employee had an expectation of privacy, or whether it was even legal for the organization to be monitoring, is simplified if the organization can point to a statement that is always displayed that instructs users that use of the system constitutes consent to monitoring. Before any monitoring is conducted, or the actual wording on the warning message is created, the organization’s legal counsel should be consulted to determine the appropriate way to address this issue in the particular jurisdiction.

In today’s highly connected environment, every organization should have an AUP that spells out to all employees what the organization considers appropriate and inappropriate use of its computing and networks resources. Having this policy may be critical should the organization need to take disciplinary actions based on an abuse of its resources.

Internet Usage Policy In today’s highly connected environment, employee use of access to the Internet is of particular concern. The goal of the Internet usage policy is to ensure maximum employee productivity and to limit potential liability to the organization from inappropriate use of the Internet in a workplace. The Internet provides a tremendous temptation for employees to waste hours as they surf the Web for the scores of games from the previous night, conduct quick online stock transactions, or read the review of the latest blockbuster movie everyone is talking about. In addition, allowing employees to visit sites that may be considered offensive to others (such as pornographic or hate sites) can open the company to accusations of condoning a hostile work environment and result in legal liability. The Internet usage policy needs to address what sites employees are

allowed to visit and what sites they are not allowed to visit. If the company allows them to surf the Web during nonwork hours, the policy needs to clearly spell out the acceptable parameters, in terms of when they are allowed to do this and what sites they are still prohibited from visiting (such as potentially offensive sites). The policy should also describe under what circumstances an employee would be allowed to post something from the organization’s network on the Web (on a blog, for example). A necessary addition to this policy would be the procedure for an employee to follow to obtain permission to post the object or message.

E-Mail Usage Policy Related to the Internet usage policy is the e-mail usage policy, which deals

with what the company will allow employees to send in, or as attachments to, e-mail messages. This policy should spell out whether nonwork e-mail traffic is allowed at all or is at least severely restricted. It needs to cover the type of message that would be considered inappropriate to send to other employees (for example, no offensive language, no sex-related or ethnic jokes, no harassment, and so on). The policy should also specify any disclaimers that must be attached to an employee’s message sent to an individual outside the company. The policy should remind employees of the risks of clicking on links in e-mails, or opening attachments, as these can be social engineering attacks.

Clean Desk Policy Preventing access to information is also important in the work area. Firms with sensitive information should have a “clean desk policy” specifying that sensitive information must not be left unsecured in the work area when the worker is not present to act as custodian. Even leaving the desk area and going to the bathroom can leave information exposed and subject to compromise. The clean desk policy should identify and prohibit things that are not obvious upon first glance, such as passwords on sticky notes under keyboards and mouse pads or in unsecured desk drawers. All of these elements that demonstrate the need for a clean desk are lost if employees do not make them personal. Training for clean desk activities needs to make the issue a personal one, where consequences are understood and the workplace reinforces the positive activity.

Bring Your Own Device (BYOD) Policy Everyone seems to have a smartphone, a tablet, or other personal Internet device that they use in their personal lives. Bringing these to work is a natural extension of one’s normal activities, but this raises the question of what policies are appropriate before a firm allows these devices to connect to the corporate network and access company data. Like all other policies, planning is needed to define the appropriate pathway to the company objectives. Personal devices offer cost savings and positive user

acceptance, and in many cases these factors make allowing BYOD a sensible decision. The primary purpose of a BYOD policy is to lower the risk associated

with connecting a wide array of personal devices to a company’s network and accessing sensitive data on them. This places security, in the form of risk management, as a center element of a BYOD policy. Devices need to be maintained in a current, up-to-date software posture, and with certain security features, such as screen locks and passwords enabled. Remote wipe and other features should be enabled, and highly sensitive data, especially in aggregate, should not be allowed on the devices. Users should have specific training as to what is allowed and what isn’t and should be made aware of the increased responsibility associated with a mobile means of accessing corporate resources. In some cases it may be necessary to define a policy associated with

personally owned devices. This policy will describe the rules and regulations associated with use of personally owned devices with respect to corporate data, network connectivity, and security risks.

Privacy Policy Customers place an enormous amount of trust in organizations to which they provide personal information. These customers expect their information to be kept secure so that unauthorized individuals will not gain access to it and so that authorized users will not use the information in unintended ways. Organizations should have a privacy policy that explains what their guiding principles will be in guarding personal data to which they are given access. A special category of private information that is becoming increasingly

important today is personally identifiable information (PII). This category of information includes any data that can be used to uniquely identify an individual. This would include an individual’s name, address, driver’s license number, and other details. An organization that collects PII on its employees and customers must make sure that it takes all necessary measures to protect the data from compromise.

Cross Check Privacy Privacy is an important consideration in today’s computing environment. As such, it has been given its own chapter, Chapter 25. Additional details on privacy issues can be found there.

Tech Tip

Prudent Person Principle The concepts of due care and due diligence are connected. Due care addresses whether the organization has a minimal set of policies that provides reasonable assurance of success in maintaining security. Due diligence requires that management actually do something to ensure security, such as implement procedures for testing and review of audit records, internal security controls, and personnel behavior. The standard applied is one of a “prudent person”; would a prudent person find the actions appropriate and sincere? To apply this standard, all one has to do is ask the following question for the issue under consideration: “What would a prudent person do to protect and ensure that the security features and procedures are working or adequate?” Failure of a security feature or procedure doesn’t necessarily mean the person acted imprudently.

Due Care and Due Diligence Due care and due diligence are terms used in the legal and business community to define reasonable behavior. Basically, the law recognizes the responsibility of an individual or organization to act reasonably relative to another party. If party A alleges that the actions of party B have caused it loss or injury, party A must prove that party B failed to exercise due care or due diligence and that this failure resulted in the loss or injury. These terms often are used synonymously, but due care generally refers to the standard of care a reasonable person is expected to exercise in all situations, whereas due diligence generally refers to the standard of care a business is expected to exercise in preparation for a business transaction. An organization must take reasonable precautions before entering a

business transaction or it might be found to have acted irresponsibly. In terms of security, organizations are expected to take reasonable precautions to protect the information that they maintain on individuals. Should a person suffer a loss as a result of negligence on the part of an organization in terms of its security, that person typically can bring a legal suit against the organization. The standard applied—reasonableness—is extremely subjective and

often is determined by a jury. The organization will need to show that it had taken reasonable precautions to protect the information, and that, despite these precautions, an unforeseen security event occurred that caused the injury to the other party. Since this is so subjective, it is hard to describe what would be considered reasonable, but many sectors have a set of “security best practices” for their industry, which provides a basis for organizations in that sector to start from. If the organization decides not to follow any of the best practices accepted by the industry, it needs to be prepared to justify its reasons in court should an incident occur. If the sector the organization is in has regulatory requirements, justifying why the mandated security practices were not followed will be much more difficult (if not impossible).

Due diligence is the application of a specific standard of care. Due care is the degree of care that an ordinary person would exercise.

Due Process Due process is concerned with guaranteeing fundamental fairness, justice, and liberty in relation to an individual’s legal rights. In the United States, due process is concerned with the guarantee of an individual’s rights as outlined by the Constitution and Bill of Rights. Procedural due process is based on the concept of what is “fair.” Also of interest is the recognition by courts of a series of rights that are not explicitly specified by the

Constitution but that the courts have decided are implicit in the concepts embodied by the Constitution. An example of this is an individual’s right to privacy. From an organization’s point of view, due process may come into play during an administrative action that adversely affects an employee. Before an employee is terminated, for example, were all of the employee’s rights protected? An actual example pertains to the rights of privacy regarding employees’ e-mail messages. As the number of cases involving employers examining employee e-mails grows, case law continues to be established and the courts eventually will settle on what rights an employee can expect. The best thing an employer can do if faced with this sort of situation is to work closely with HR staff to ensure that appropriate policies are followed and that those policies are in keeping with current laws and regulations.

Incident Response Policies and Procedures No matter how careful an organization is, eventually a security incident of some sort will occur. When it happens, how effectively the organization responds to it will depend greatly on how prepared it is to handle incidents. An incident response policy and associated procedures should be developed to outline how the organization will prepare for security incidents and respond to them when they occur. Waiting until an incident happens is not the right time to establish your policies—they need to be designed in advance. The incident response policy should cover five phases: preparation, detection, containment and eradication, recovery, and follow-up actions.

Cross Check Incident Response Incident response is covered in detail in Chapter 22. This section serves only as an introduction to policy elements associated with the topic. For complete details on incident response, please examine Chapter 22.

Security Awareness and Training Security awareness and training programs can enhance an organization’s security posture in two direct ways. First, they teach personnel how to follow the correct set of actions to perform their duties in a secure manner. Second, they make personnel aware of the indicators and effects of social engineering attacks. There are many tasks that employees perform that can have information

security ramifications. Properly trained employees are able to perform their duties in a more effective manner, including their duties associated with information security. The extent of information security training will vary depending on the organization’s environment and the level of threat, but initial employee security training at the time of being hired is important, as is periodic refresher training. A strong security education and awareness training program can go a long way toward reducing the chance that a social engineering attack will be successful. Security awareness programs and campaigns, which might include seminars, videos, posters, newsletters, and similar materials, are also fairly easy to implement and are not very costly.

Security Policy Training and Procedures Personnel cannot be expected to perform complex tasks without training with respect to the tasks and expectations. This applies both to the security policy and to operational security details. If employees are going to be expected to comply with the organization’s security policy, they must be properly trained in its purpose, meaning, and objectives. Training with respect to the information security policy, individual responsibilities, and expectations is something that requires periodic reinforcement through refresher training. Because the security policy is a high-level directive that sets the overall

support and executive direction with respect to security, it is important that the meaning of this message be translated and supported. Second-level

policies such as password, access, information handling, and acceptable use policies also need to be covered. The collection of policies should paint a picture describing the desired security culture of the organization. The training should be designed to ensure that people see and understand the whole picture, not just the elements.

Role-based Training For training to be effective, it needs to be targeted to the user with regard to their role in the subject of the training. While all employees may need general security awareness training, they also need specific training in areas where they have individual responsibilities. Role-based training with regard to information security responsibilities is an important part of information security training. If a person has job responsibilities that may impact information security,

then role-specific training is needed to ensure that the individual understands the responsibilities as they relate to information security. Some roles, such as system administrator or developer, have clearly defined information security responsibilities. The roles of others, such as project manager or purchasing manager, have information security impacts that are less obvious, but these roles require training as well. In fact, the less-obvious but wider-impact roles of middle management can have a large effect on the information security culture, and thus if a specific outcome is desired, it requires training. As in all personnel-related training, two elements need attention. First,

retraining over time is necessary to ensure that personnel keep proper levels of knowledge. Second, as people change jobs, a reassessment of the required training basis is needed, and additional training may be required. Maintaining accurate training records of personnel is the only way this can be managed in any significant enterprise.

Compliance with Laws, Best Practices, and

Standards There is a wide array of laws, regulations, contractual requirements, standards, and best practices associated with information security. Each places its own set of requirements upon an organization and its personnel. The only effective way for an organization to address these requirements is to build them into their own policies and procedures. Training to one’s own policies and procedures would then translate into coverage of these external requirements. It is important to note that many of these external requirements impart a

specific training and awareness component upon the organization. Organizations subject to the requirements of the Payment Card Industry Data Security Standard (PCI DSS), Gramm Leach Bliley Act (GLBA), or Health Insurance Portability Accountability Act (HIPAA) are among the many that must maintain a specific information security training program. Other organizations should do so as a matter of best practice.

User Habits Individual user responsibilities vary between organizations and the type of business each organization is involved in, but there are certain very basic responsibilities that all users should be instructed to adopt:

Lock the door to your office or workspace, including drawers and cabinets.

Do not leave sensitive information inside your car unprotected.

Secure storage media containing sensitive information in a secure storage device.

Shred paper containing organizational information before discarding it.

Do not divulge sensitive information to individuals (including other employees) who do not have an authorized need to know it.

Do not discuss sensitive information with family members. (The most common violation of this rule occurs in regard to HR information, as employees, especially supervisors, may complain to their spouse or friends about other employees or about problems that are occurring at work.)

Protect laptops and other mobile devices that contain sensitive or important organization information wherever the device may be stored or left. (It’s a good idea to ensure that sensitive information is encrypted on the laptop or mobile device so that, should the equipment be lost or stolen, the information remains safe.)

Be aware of who is around you when discussing sensitive corporate information. Does everybody within earshot have the need to hear this information?

Enforce corporate access control procedures. Be alert to, and do not allow, piggybacking, shoulder surfing, or access without the proper credentials.

Be aware of the correct procedures to report suspected or actual violations of security policies.

Follow procedures established to enforce good password security practices. Passwords are such a critical element that they are frequently the ultimate target of a social engineering attack. Though such password procedures may seem too oppressive or strict, they are often the best line of defense.

User habits are a front-line security tool in engaging the workforce to improve the overall security posture of an organization.

User responsibilities are easy training topics about which to ask questions on the CompTIA Security+ exam, so commit to memory your knowledge of the points listed here.

New Threats and Security Trends/Alerts At the end of the day, information security practices are about managing risk, and it is well known that the risk environment is one marked by constant change. The ever-evolving threat environment frequently encounters new threats, new security issues, and new forms of defense. Training people to recognize the new threats necessitates continual awareness and training refresher events.

New Viruses New forms of viruses, or malware, are being created every day. Some of these new forms can be highly destructive and costly, and it is incumbent upon all users to be on the lookout for and take actions to avoid exposure. Poor user practices are counted on by malware authors to assist in the spread of their attacks. One way of explaining proper actions to users is to use an analogy to cleanliness. Training users to practice good hygiene in their actions can go a long way toward assisting the enterprise in defending against these attack vectors.

Phishing Attacks The best defense against phishing and other social engineering attacks is an educated and aware body of employees. Continual refresher training about the topic of social engineering and specifics about current attack trends are needed to keep employees aware of and prepared for new trends in social engineering attacks. Attackers rely upon an uneducated, complacent, or distracted workforce to enable their attack vector. Social engineering has become the gateway for many of the most damaging attacks in play today. Social engineering is covered extensively in Chapter 4.

Social Networking and P2P With the rise in popularity of peer-to-peer (P2P) communications and

social networking sites—notably Facebook, Twitter, and LinkedIn—many people have gotten into a habit of sharing too much information. Using a status of “Returning from sales call to XYZ company” reveals information to people who have no need to know this information. Confusing sharing with friends and sharing business information with those who don’t need to know is a line people are crossing on a regular basis. Don’t be the employee who mixes business and personal information and releases information to parties who should not have it, regardless of how innocuous it may seem. Users need to understand the importance of not using common programs

such as torrents and other file sharing in the workplace, as these programs can result in infection mechanisms and data-loss channels. The information security training and awareness program should cover these issues. If the issues are properly explained to employees, their motivation to comply won’t simply be to avoid adverse personnel action for violating a policy; they will want to assist in the security of the organization and its mission.

Training Metrics and Compliance Training and awareness programs can yield much in the way of an educated and knowledgeable workforce. Many laws, regulations, and best practices have requirements for maintaining a trained workforce. Having a record-keeping system to measure compliance with attendance and to measure the effectiveness of the training is a normal requirement. Simply conducting training is not sufficient. Following up and gathering training metrics to validate compliance and security posture is an important aspect of security training management. A number of factors deserve attention when managing security training.

Because of the diverse nature of role-based requirements, maintaining an active, up-to-date listing of individual training and retraining requirements is one challenge. Monitoring the effectiveness of the training is yet another challenge. Creating an effective training and awareness program when

measured by actual impact on employee behavior is a challenging endeavor. Training needs to be current, relevant, and interesting to engage employee attention. Simple repetition of the same training material has not proven to be effective, so regularly updating the program is a requirement if it is to remain effective over time.

Tech Tip

Security Training Records Requirements for both periodic training and retraining drive the need for good training records. Maintaining proper information security training records is a requirement of several laws and regulations and should be considered a best practice.

Interoperability Agreements Many business operations involve actions between many different parties —some within an organization, and some in different organizations. These actions require communication between the parties, defining the responsibilities and expectations of the parties, the business objectives, and the environment within which the objectives will be pursued. To ensure an agreement is understood between the parties, written agreements are used. Numerous forms of legal agreements and contracts are used in business, but with respect to security, some of the most common ones are the service level agreement, business partnership agreement, memorandum of understanding, and interconnection security agreement.

Service Level Agreements Service level agreements (SLAs) are contractual agreements between entities that describe specified levels of service that the servicing entity agrees to guarantee for the customer. SLAs essentially set the requisite

level of performance of a given contractual service. SLAs are typically included as part of a service contract and set the level of technical expectations. An SLA can define specific services, the performance level associated with a service, issue management and resolution, and so on. SLAs are negotiated between customer and supplier and represent the agreed-upon terms. An organization contracting with a service provider should remember to include in the agreement a section describing the service provider’s responsibility in terms of business continuity and disaster recovery. The provider’s backup plans and processes for restoring lost data should also be clearly described. Typically, a good SLA will satisfy two simple rules. First, it will

describe the entire set of product or service functions in sufficient detail that their requirement will be unambiguous. Second, the SLA will provide a clear means of determining whether a specified function or service has been provided at the agreed-upon level of performance.

Business Partnership Agreement A business partnership agreement (BPA) is a legal agreement between partners establishing the terms, conditions, and expectations of the relationship between the partners. These details can cover a wide range of issues, including typical items such as the sharing of profits and losses, the responsibilities of each partner, the addition or removal of partners, and any other issues. The Uniform Partnership Act (UPA), established by state law and convention, lays out a uniform set of rules associated with partnerships to resolve any partnership terms. The terms in a UPA are designed as “one size fits all” and are not typically in the best interest of any specific partnership. To avoid undesired outcomes that may result from UPA terms, it is best for partnerships to spell out specifics in a BPA.

Memorandum of Understanding A memorandum of understanding (MOU) is a legal document used to

describe a bilateral agreement between parties. It is a written agreement expressing a set of intended actions between the parties with respect to some common pursuit or goal. It is more formal and detailed than a simple handshake, but it generally lacks the binding powers of a contract. It is also common to find MOUs between different units within an organization to detail expectations associated with the common business interest.

Interconnection Security Agreement An interconnection security agreement (ISA) is a specialized agreement between organizations that have interconnected IT systems, the purpose of which is to document the security requirements associated with the interconnection. An ISA can be a part of an MOU detailing the specific technical security aspects of a data interconnection.

Be sure you understand the differences between the interoperability agreements SLA, BPA, MOU, and ISA. The differences hinge upon the purpose for each document.

The Security Perimeter The discussion to this point has not included any mention of the specific technology used to enforce operational and organizational security or a description of the various components that constitute the organization’s security perimeter. If the average administrator were asked to draw a diagram depicting the various components of their network, the diagram would probably look something like Figure 3.1.

• Figure 3.1 Basic diagram of an organization’s network

The security perimeter, with its several layers of security, along with additional security mechanisms that may be implemented on each system (such as user IDs/passwords), creates what is sometimes known as defense-in-depth. This implies that security is enhanced when there are multiple layers of security (the depth) through which an attacker would have to penetrate to reach the desired goal.

This diagram includes the major components typically found in a network. The connection to the Internet generally has some sort of protection attached to it such as a firewall. An intrusion detection system (IDS), also often part of the security perimeter for the organization, may be either on the inside or the outside of the firewall, or it may in fact be on both sides. The specific location depends on the company and what it is

more concerned about preventing (that is, insider threats or external threats). The router can also be thought of as a security device, as it can be used to enhance security such as in the case of wireless routers that can be used to enforce encryption settings. Beyond this security perimeter is the corporate network. Figure 3.1 is obviously a very simple depiction—an actual network can have numerous subnets and extranets as well as wireless access points—but the basic components are present. Unfortunately, if this were the diagram provided by the administrator to show the organization’s basic network structure, the administrator would have missed a very important component. A more astute administrator would provide a diagram more like Figure 3.2.

• Figure 3.2 A more complete diagram of an organization’s network

This diagram includes other possible access points into the network, including the public switched telephone network (PSTN) and wireless access points. The organization may or may not have any authorized modems or wireless networks, but the savvy administrator would realize that the potential exists for unauthorized versions of both. When considering the policies, procedures, and guidelines needed to implement

security for the organization, both networks need to be considered. Another development that has brought the telephone and computer networks together is the implementation of voice over IP (VoIP), which eliminates the traditional land lines in an organization and replaces them with special telephones that connect to the IP data network. While Figure 3.2 provides a more comprehensive view of the various

components that need to be protected, it is still incomplete. Most experts will agree that the biggest danger to any organization does not come from external attacks but rather from the insider—a disgruntled employee or somebody else who has physical access to the facility. Given physical access to an office, the knowledgeable attacker will quickly find the information needed to gain access to the organization’s computer systems and network. Consequently, every organization also needs security policies, procedures, and guidelines that cover physical security, and every security administrator should be concerned with these as well. While physical security (which can include such things as locks, cameras, guards and entry points, alarm systems, and physical barriers) will probably not fall under the purview of the security administrator, the operational state of the organization’s physical security measures is just as important as many of the other network-centric measures.

An increasing number of organizations are implementing VoIP solutions to bring the telephone and computer networks together. While there are some tremendous advantages to doing this in terms of both increased capabilities and potential monetary savings, bringing the two networks together may also introduce additional security concerns. Another common method to access organizational networks today is through wireless access points. These may be provided by the organization itself to enhance productivity, or they may be attached to the network by users without organizational approval. The impact of all of these additional methods that can be used to access a network is to increase the complexity of the security problem.

Physical Security

Physical security consists of all mechanisms used to ensure that physical access to the computer systems and networks is restricted to only authorized users. Additional physical security mechanisms may be used to provide increased security for especially sensitive systems such as servers and devices such as routers, firewalls, and intrusion detection systems. When considering physical security, access from all six sides should be considered—not only should the security of obvious points of entry be examined, such as doors and windows, but the walls themselves as well as the floor and ceiling should also be considered. Questions such as the following should be addressed:

Is there a false ceiling with tiles that can be easily removed?

Do the walls extend to the actual ceiling or only to a false ceiling?

Is there a raised floor?

Do the walls extend to the actual floor, or do they stop at a raised floor?

How are important systems situated?

Do the monitors face away from windows, or could the activity of somebody at a system be monitored?

Who has access to the facility?

What type of access control is there, and are there any guards?

Who is allowed unsupervised access to the facility?

Is there an alarm system or security camera that covers the area?

What procedures govern the monitoring of the alarm system or security camera and the response should unauthorized activity be detected?

These are just some of the numerous questions that need to be asked when examining the physical security surrounding a system.

Tech Tip

Physical Security Is Also Important to Computer Security Computer security professionals recognize that they cannot rely only on computer security mechanisms to keep their systems safe. Physical security must be maintained as well, because in many cases, if an attacker gains physical access, he can steal data and destroy the system.

Physical Access Controls The purpose of physical access controls is the same as that of computer and network access controls—you want to restrict access to only those who are authorized to have it. Physical access is restricted by requiring the individual to somehow authenticate that they have the right or authority to have the desired access. As in computer authentication, access in the physical world can be based on something the individual has, something they know, or something they are. Frequently, when dealing with the physical world, the terms “authentication” and “access control” are used interchangeably. The most common physical access control device, which has been

around in some form for centuries, is a lock. Combination locks represent an access control device that depends on something the individual knows (the combination). Locks with keys depend on something the individual has (the key). Each of these has certain advantages and disadvantages. Combinations don’t require any extra hardware, but they must be remembered (which means individuals may write them down—a security vulnerability in itself) and are hard to control. Anybody who knows the combination may provide it to somebody else. Key locks are simple and easy to use, but the key may be lost, which means another key has to be made or the lock has to be rekeyed. Keys may also be copied, and their dissemination can be hard to control. Newer locks replace the traditional key with a card that must be passed through a reader or placed against it. The individual may also have to provide a personal access code, thus

making this form of access both a something-you-know and something- you-have method.

Tech Tip

Physical and Information Security Convergence In high-security sites, physical access controls and electronic access controls to information are interlocked. This means that before data can be accessed from a particular machine, the physical access control system must agree with the finding that the authorized party is present.

In addition to locks on doors, other common physical security devices include video surveillance and even simple access control logs (sign-in logs). While sign-in logs don’t provide an actual barrier, they do provide a record of access and, when used in conjunction with a guard who verifies an individual’s identity, can dissuade potential adversaries from attempting to gain access to a facility. As mentioned, another common access control mechanism is a human security guard. Many organizations employ a guard to provide an extra level of examination of individuals who want to gain access to a facility. Other devices are limited to their designed function. A human guard can apply common sense to situations that might have been unexpected. Having security guards also addresses the common practice of piggybacking (aka tailgating), where an individual follows another person closely to avoid having to go through the access control procedures.

Biometrics Access controls that utilize something you know (for example, combinations) or something you have (such as keys) are not the only methods to limit facility access to authorized individuals. A third approach is to utilize something unique about the individual—their fingerprints, for example—to identify them. Unlike the other two methods, the something- you-are method, known as biometrics, does not rely on the individual to

either remember something or to have something in their possession. Biometrics is a more sophisticated access control approach and can be more expensive. Biometrics also suffer from false positives and false negatives, making them less than 100 percent effective. For this reason they are frequently used in conjunction with another form of authentication. The advantage is the user always has them (cannot leave at home or share) and they tend to have better entropy than passwords. Other methods to accomplish biometrics include handwriting analysis, retinal scans, iris scans, voiceprints, hand geometry, and facial geometry.

There are many similarities between authentication and access controls in computers and in the physical world. Remember the three common techniques for verifying a person’s identity and access privileges: something you know, something you have, and something about you.

Both access to computer systems and networks and physical access to restricted areas can be controlled with biometrics. However, biometric methods for controlling physical access are generally not the same as those employed for restricting access to computer systems and networks. Hand geometry, for example, requires a fairly large device. This can easily be placed outside of a door to control access to the room but would not be as convenient to control access to a computer system, since a reader would need to be placed with each computer or at least with groups of computers. In a mobile environment where laptops are being used, a device such as a hand geometry reader would be unrealistic.

Tech Tip

Biometric Devices Once only seen in spy or science fiction movies, biometrics such as hand and fingerprint readers, eye-scanning technology, and voiceprint devices are now becoming more common in the real world. The accuracy of these devices has improved and the costs have dropped,

making them realistic solutions to many access control situations.

Physical Barriers An even more common security feature than locks is a physical barrier. Physical barriers help implement the physical-world equivalent of layered security. The outermost layer of physical security should contain the more publicly visible activities. A guard at a gate in a fence, for example, would be visible by all who happen to pass by. As you progress through the layers, the barriers and security mechanisms should become less publicly visible to make determining what mechanisms are in place more difficult for observers. Signs are also an important element in security, as they announce to the public which areas are public and which are private. A man trap can also be used in this layered approach. It generally consists of a small space that is large enough for only one person at a time, with two locking doors. An individual has to enter the first door, close the first door, then attempt to open the second door. If unsuccessful, perhaps because they do not have the proper access code, the person can be caught inside this small location until security personnel show up. In addition to walls and fences, open space can also serve as a barrier.

While this may at first seem to be an odd statement, consider the use of large areas of open space around a facility. For an intruder to cross this open space takes time—time in which they are vulnerable and their presence may be discovered. In today’s environment in which terrorist attacks have become more common, additional precautions should be taken for areas that may be considered a possible target for terrorist activity. In addition to open space, which is necessary to lessen the effect of explosions, concrete barriers that stop vehicles from getting too close to facilities should also be used. It is not necessary for these to be unsightly concrete walls; many facilities have placed large, round concrete circles, filled them with dirt, and then planted flowers and other plants to construct a large, immovable planter.

Tech Tip

Signs Signs can be an effective control, warning unauthorized personnel not to enter, locating critical elements for first responders, and providing paths to exits in emergencies. Proper signage is an important aspect of physical security controls.

Environmental Issues Environmental issues may not at first seem to be related to security, but when considering the availability of a computer system or network, they must be taken into consideration. Environmental issues include items such as heating, ventilation, and air conditioning (HVAC) systems, electrical power, and the “environments of nature.” HVAC systems are used to maintain the comfort of an office environment. A few years back, they were also critical for the smooth operation of computer systems that had low tolerances for humidity and heat. Today’s desktop systems are much more tolerant, and the limiting factor is now often the human user. The exception to this HVAC limitation is when large quantities of equipment are co-located, in server rooms and network equipment closets. In these heat-dense areas, HVAC is needed to keep equipment temperatures within reasonable ranges. Often certain security devices such as firewalls and intrusion detection systems are located in these same equipment closets and the loss of HVAC systems can cause these critical systems to fail. One interesting aspect of HVAC systems is that they themselves are often computer controlled and frequently provide remote access via telephone or network connections. These connections should be protected in a similar manner to computer modems, or else attackers may locate them and change the HVAC settings for an office or building.

HVAC systems for server rooms and network equipment closets are important because the dense equipment environment can generate significant amounts of heat. HVAC outages can result in temperatures that are outside equipment operating ranges, forcing shutdowns.

Electrical power is obviously an essential requirement for computer systems and networks. Electrical power is subject to momentary surges and disruption. Surge protectors are needed to protect sensitive electronic equipment from fluctuations in voltage. An uninterruptible power supply (UPS) should be considered for critical systems so that a loss of power will not halt processing. The size of the batteries associated with a UPS will determine the amount of time that it can operate before it too loses power. Many sites ensure sufficient power to provide administrators the opportunity to cleanly bring the system or network down. For installations that require continuous operations, even in the event of a power outage, electric generators that automatically start when a loss of power is detected can be installed. These systems may take a few seconds to start before they reach full operation, so a UPS should also be considered to smooth the transition between normal and backup power.

Fire Suppression Fires are a common disaster that can affect organizations and their computing equipment. Fire detection and fire suppression devices are two approaches to addressing this threat. Detectors can be useful because some may be able to detect a fire in its very early stages before a fire suppression system is activated, and they can potentially sound a warning. This warning could provide employees with the opportunity to deal with the fire before it becomes serious enough for the fire suppression equipment to kick in. Suppression systems come in several varieties, including sprinkler-based systems and gas-based systems. Standard sprinkler-based systems are not optimal for data centers because water will

ruin large electrical infrastructures and most integrated circuit–based devices—such as computers. Gas-based systems are a good alternative, though they also carry special concerns. More extensive coverage of fire detection and suppression is provided in Chapter 8.

Wireless When someone talks about wireless communication, they generally are referring to cellular telephones (“cell phones”). These devices have become ubiquitous in today’s modern office environment. A cell phone network consists of the phones themselves, the cells with their accompanying base stations that they are used in, and the hardware and software that allow them to communicate. The base stations are made up of antennas, receivers, transmitters, and amplifiers. The base stations communicate with those cell phones that are currently in the geographical area that is serviced by that station. As a person travels across town, they may exit and enter multiple cells. The stations must conduct a handoff to ensure continuous operation for the cell phone. As the individual moves toward the edge of a cell, a mobile switching center notices the power of the signal beginning to drop, checks whether another cell has a stronger signal for the phone (cells frequently overlap), and, if so, switches operation to this new cell and base station. All of this is done without the user ever knowing that they have moved from one cell to another. Wireless technology can also be used for networking. There are two

main standards for wireless network technology. Bluetooth is designed as a short-range (approximately ten meters) personal area network (PAN) cable-replacement technology that can be built into a variety of devices, such as mobile phones, tablets, and laptop computers. The idea is to create low-cost wireless technology so that many different devices can communicate with each other. Bluetooth is also interesting because, unlike other wireless technology, it is designed so that devices can talk directly with each other without having to go through a central device (such as the base station described previously). This is known as peer-to-peer

communication.

Tech Tip

Wireless Network Security Issues Due to a number of advantages, such as the ability to take your laptop with you as you move around your building and still stay connected, wireless networks have grown in popularity. They also eliminate the need to string network cables all over the office. At the same time, however, they can be a security nightmare if not adequately protected. The signal for your network doesn’t stop at your office door or wall just because it is there. It will continue propagating to areas that may be open to anybody. This provides the opportunity for others to access your network. To avoid this, you must take steps such as encrypting transmissions so that your wireless network doesn’t become the weak link in your security chain.

The other major wireless standard is the IEEE 802.11 set of standards, which is well suited for the local area network (LAN) environment. 802.11 networks can operate either in an ad hoc peer-to-peer fashion or in infrastructure mode, which is more common. In infrastructure mode, computers with 802.11 network cards communicate with a wireless access point. This access point connects to the network so that the computers communicating with it are essentially also connected to the network. While wireless networks are very useful in today’s modern office (and

home), they are not without their security problems. Access points are generally placed throughout a building so that all employees can access the corporate network. The transmission and reception areas covered by access points are not easily controlled. Consequently, many publicly accessible areas might fall into the range of one of the organization’s access points, or its Bluetooth-enabled systems, and thus the corporate network may become vulnerable to attack. Wireless networks are designed to incorporate some security measures, but all too often the networks are set up without security enabled, and serious security flaws exist in the 802.11 design.

Cross Check Wireless Networks Wireless network security is discussed in this chapter in relationship to physical issues such as the placement of wireless access points. There are, however, numerous other issues with wireless security, which are discussed in Chapter 12. Make sure to understand how the physical location of wireless access points affects the other wireless security issues.

Electromagnetic Eavesdropping In 1985, a paper by Wim van Eck of the Netherlands described what became known as the van Eck phenomenon. In the paper van Eck described how eavesdropping on what was being displayed on monitors could be accomplished by picking up and then decoding the electromagnetic interference produced by the monitors. With the appropriate equipment, the exact image of what is being displayed can be re-created some distance away. While the original paper discussed emanations as they applied to video display units (monitors), the same phenomenon applies to other devices such as printers and computers. This phenomenon had actually been known about for quite some time

before van Eck published his paper. The U.S. Department of Defense used the term TEMPEST (referred to by some as the Transient ElectroMagnetic Pulse Emanation STandard) to describe both a program in the military to control these electronic emanations from electrical equipment and the actual process for controlling the emanations. There are three basic ways to prevent these emanations from being picked up by an attacker:

Put the equipment beyond the point that the emanations can be picked up.

Provide shielding for the equipment itself.

Provide a shielded enclosure (such as a room) to put the equipment in.

One of the simplest ways to protect against equipment being monitored in this fashion is to put enough distance between the target and the attacker. The emanations can be picked up from only a limited distance. If the physical security for the facility is sufficient to put enough space between the equipment and publicly accessible areas that the signals cannot be picked up, then the organization doesn’t have to take any additional measures to ensure security. Distance is not the only way to protect against eavesdropping on

electronic emanations. Devices can be shielded so their emanations are blocked. Acquiring enough property to provide the necessary distance needed to protect against an eavesdropper may be possible if the facility is in the country with lots of available land surrounding it. Indeed, for smaller organizations that occupy only a few offices or floors in a large office building, it would be impossible to acquire enough space. In this case, the organization may resort to purchasing shielded equipment. A “TEMPEST approved” computer will cost significantly more than what a normal computer would cost. Shielding a room (in what is known as a Faraday cage) is also an extremely expensive endeavor.

One of the challenges in security is determining how much to spend on security without spending too much. Security spending should be based on likely threats to your systems and network. While electronic emanations can be monitored, the likelihood of this taking place in most situations is remote, which makes spending on items to protect against it at best a low priority.

A natural question to ask is, how prevalent is this form of attack? The equipment needed to perform electromagnetic eavesdropping is not readily available, but it would not cost an inordinate amount of money to produce it. The cost could certainly be afforded by any large corporation, and industrial espionage using such a device is a possibility. While there are no public records of this sort of activity being conducted, it is reasonable to assume that it does take place in large corporations and the government, especially in foreign countries.

Modern Eavesdropping Not just electromagnetic information can be used to carry information out of a system to an adversary. Recent advances have demonstrated the feasibility of using the webcams and microphones on systems to spy on users, recording keystrokes and other activities. There are even devices built to intercept the wireless signals between wireless keyboards and mice and transmit them over another channel to an adversary. USB-based keyloggers can be placed in the back of machines, as in many cases the back of a machine is unguarded or facing the public (watch for this the next time you see a receptionist’s machine).

Chapter 3 Review

Chapter Summary After reading this chapter and completing the exercises, you should understand the following regarding operational and organizational security.

Identify various operational aspects to security in your organization

Prevention technologies are designed to keep individuals from being able to gain access to systems or data they are not authorized to use.

Previously in operational environments, prevention was extremely difficult and relying on prevention technologies alone was not sufficient. This led to the rise of technologies to detect and respond to events that occur when prevention fails.

An important part of any organization’s approach to implementing security is to establish policies, procedures, standards, and guidelines to detail what users and administrators should be doing to maintain the

security of the systems and network.

Identify various policies and procedures in your organization

Policies, procedures, standards, and guidelines are important in establishing a security program within an organization.

The security policy and supporting policies play an important role in establishing and managing system risk.

Policies and procedures associated with Human Resources functionality include job rotation, mandatory vacations, and hiring and termination policies.

Identify the security awareness and training needs of an organization

Security training and awareness efforts are vital in engaging the workforce to act within the desired range of conduct with respect to security.

Security awareness and training is important in achieving compliance objectives.

Security awareness and training should be measured and managed as part of a comprehensive security program.

Understand the different types of agreements employed in negotiating security requirements

The different interoperability agreements, including SLA, BPA, MOU and ISA, are used to establish security expectations between various parties.

Describe the physical security components that can protect your computers and network

Physical security consists of all mechanisms used to ensure that physical access to the computer systems and networks is restricted to

only authorized users.

The purpose of physical access controls is the same as that of computer and network access controls—to restrict access to only those who are authorized to have it.

The careful placement of equipment can provide security for known security problems exhibited by wireless devices and that arise due to electronic emanations.

Identify environmental factors that can affect security

Environmental issues are important to security because they can affect the availability of a computer system or network.

Loss of HVAC systems can lead to overheating problems that can affect electronic equipment, including security-related devices.

The frequency of natural disasters is a contributing factor that must be considered when making contingency processing plans for an installation.

Fires are a common problem for organizations. Two general approaches to addressing this problem are fire detection and fire suppression.

Identify factors that affect the security of the growing number of wireless technologies used for data transmission

Wireless networks have many security issues, including the transmission and reception areas covered by access points, which are not easily controlled and can thus provide easy network access for intruders.

Prevent disclosure through electronic emanations

With the appropriate equipment, the exact image of what is being displayed on a computer monitor can be re-created some distance

away, allowing eavesdroppers to view what you are doing.

Providing a lot of distance between the system you wish to protect and the closest place an eavesdropper could be is one way to protect against eavesdropping on electronic emanations. Devices can also be shielded so that their emanations are blocked.

Key Terms acceptable use policy (AUP) (50) biometrics (62) Bluetooth (65) business partnership agreement (BPA) (59) due care (53) due diligence (53) guidelines (43) heating, ventilation, and air conditioning (HVAC) (63) IEEE 802.11 (65) incident response policy (54) interconnection security agreement (ISA) (59) memorandum of understanding (MOU) (59) physical security (61) policies (43) procedures (43) security policy (44) service level agreement (SLA) (59) standards (43) TEMPEST (66) uninterruptible power supply (UPS) (64) user habits (57)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. _______________ are high-level statements made by management that lay out the organization’s position on some issue.

2. The collective term used to refer to the systems that are used to maintain the comfort of an office environment and that are often controlled by computer systems is _______________.

3. A(n) _______________ is a device designed to provide power to essential equipment for a period of time when normal power is lost.

4. _______________ are a foundational security tool in engaging the workforce to improve the overall security posture of an organization.

5. _______________ are accepted specifications providing specific details on how a policy is to be enforced.

6. _______________ is a wireless technology designed as a short- range (approximately ten meters) personal area network (PAN) cable-replacement technology that may be built into a variety of devices such as mobile phones, tablets, and laptop computers.

7. A(n) _______________ is a legal document used to describe a bilateral agreement between parties.

8. _______________ are step-by-step instructions that describe exactly how employees are expected to act in a given situation or to accomplish a specific task.

9. The set of standards for wireless networks that is well suited for the LAN environment and whose normal mode is to have computers with network cards communicating with a wireless access point is _______________.

10. A(n) _______________ is a legal agreement between organizations establishing the terms, conditions, and expectations of the relationship between them.

Multiple-Choice Quiz 1. Which of the following is a physical security threat?

A. Cleaning crews are allowed unsupervised access because they have a contract.

B. Employees undergo background criminal checks before being hired.

C. All data is encrypted before being backed up.

D. All the above.

2. The benefit of fire detection equipment over fire suppression devices is:

A. Fire detection equipment is regulated, whereas fire suppression equipment is not.

B. Fire detection equipment will often catch fires at a much earlier stage, meaning that the fire can be addressed before significant damage can occur.

C. Fire detection equipment is much more reliable than fire suppression equipment.

D. There is no advantage of fire detection over fire suppression other than the cost of fire detection equipment is much less than the cost of fire suppression equipment.

3. Which of the following is a contractual agreement between entities that describes specified levels of service that the servicing entity agrees to guarantee for the customer?

A. Service level agreement

B. Support level agreement

C. Memorandum of understanding

D. Business service agreement

4. During which step of the policy lifecycle does training of users take place?

A. Plan for security.

B. Implement the plans.

C. Monitor the implementation.

D. Evaluate for effectiveness.

5. Biometric access controls are typically used in conjunction with another form of access control because:

A. Biometrics are still expensive.

B. Biometrics cannot be copied.

C. Biometrics are not always convenient to use.

D. Biometrics are not 100 percent accurate, having some level of misidentifications.

6. Procedures can be described as: A. High-level, broad statements of what the organization wants to

accomplish

B. Step-by-step instructions on how to implement the policies

C. Mandatory elements regarding the implementation of a policy

D. Recommendations relating to a policy

7. What technique can be used to protect against electromagnetic

eavesdropping (known as the van Eck phenomenon)?

A. Provide sufficient distance between the potential target and the nearest location an attacker could be.

B. Put the equipment that you are trying to protect inside a shielded room.

C. Purchase “TEMPEST approved” equipment.

D. All of the above.

8. Key user habits that can improve security efforts include: A. Do not discuss business issues outside of the office.

B. Never leave laptops or tablets inside your car unattended.

C. Be alert of people violating physical access rules (piggybacking through doors).

D. Items B and C.

9. When should a human security guard be used for physical access control?

A. When other electronic access control mechanisms will not be accepted by employees

B. When necessary to avoid issues such as piggybacking, which can occur with electronic access controls

C. When other access controls are too expensive to implement

D. When the organization wants to enhance its image

10. What device should be used by organizations to protect sensitive equipment from fluctuations in voltage?

A. A surge protector

B. An uninterruptible power supply

C. A backup power generator

D. A redundant array of inline batteries (RAIB)

Essay Quiz 1. Describe the difference between fire suppression and fire detection

systems.

2. Discuss why physical security is also important to computer security professionals.

3. Why should we be concerned about HVAC systems when discussing security?

4. Outline the various components that make up (or should make up) an organization’s security perimeter. Which of these can be found in your organization (or school)?

Lab Projects

• Lab Project 3.1 Take a tour of your building on campus or at work. What is secured at night when workers are absent? Record the location and type of physical access control devices. How do these access controls change at night when workers are absent? How well trained do guards and other employees appear to be? Do they allow “piggybacking” (somebody slipping into a facility behind an authorized individual without being challenged)? What are the policies for visitors and contractors? How does this all impact physical security?

• Lab Project 3.2 Describe the four steps of the policy lifecycle. Obtain a policy from your organization (such as an acceptable use policy or Internet usage policy). How are users informed of this policy? How often is it reviewed? How would changes to it be suggested and who would make decisions on whether the changes were accepted?

chapter 4 The Role of People in Security

You are the way you are because that’s the way you want to be. If you really wanted to be any different, you would be in the process of changing right now.

T

—FRED SMITH

In this chapter, you will learn how to

Define basic terminology associated with social engineering

Describe steps organizations can take to improve their security

Describe common user actions that may put an organization’s information at risk

Recognize methods attackers may use to gain information about an organization

Determine ways in which users can aid instead of detract from security

Recognize the role training and awareness plays in assisting the people side of security

he operational model of computer security discussed in the previous chapter acknowledges that absolute protection of computer systems and networks is not possible and that we need to be prepared to detect

and respond to attacks that are able to circumvent our security mechanisms. Another very basic fact that should be recognized is that technology alone will not solve the security problem. No matter how advanced the technology is, it will ultimately be deployed in an environment where humans exist. It is the human element that poses the biggest security challenge. It is hard to compensate for all of the possible ways that humans can deliberately or accidentally cause security problems or circumvent our security mechanisms. Despite all of the technology, despite all of the security procedures we have in place, and despite all of the security training we may provide, somebody will invariably fail to do what they are supposed to do, or do something they are not supposed to do, and create a vulnerability in the organization’s security posture. This chapter discusses the human element and the role that people play in security—both the user practices that can aid in securing an organization and the vulnerabilities or holes in security that users can introduce.

People—A Security Problem

The operational model of computer security acknowledges that prevention technologies are not sufficient to protect our computer systems and networks. There are a number of explanations for why this is true, some of them technical, but one of the biggest reasons that prevention technologies are not sufficient is that every network and computer system has at least one human user, and humans are prone to make mistakes and are often easily misled or fooled.

Social Engineering Social engineering, if you recall from Chapter 2, is the process of convincing an authorized individual to provide confidential information or access to an unauthorized individual. It is a technique in which the attacker uses various deceptive practices to convince the targeted person to divulge information they normally would not divulge or to convince the target of the attack to do something they normally wouldn’t do. Social engineering is very successful for two general reasons. The first is the basic desire of most people to be helpful. When somebody asks a question for which we know the answer, our normal response is not to be suspicious but rather to answer the question. The problem with this is that seemingly innocuous information can be used either directly in an attack or indirectly to build a bigger picture that an attacker can use to create an aura of authenticity during an attack—the more information an individual has about an organization, the easier it will be to convince others that he is part of the organization and has a right to even sensitive information. An attacker who is attempting to exploit the natural tendency of people to be helpful may take one of several approaches:

Tech Tip

Social Engineering Works! Skilled social engineers set up scenarios where the victim is boxed in by various social/work

issues and then makes an exception that enables the social engineer to gain some form of access. The attacker can pretend to be an important party and intimidate a lower-level employee, or create a sense of emergency, scarcity, or urgency that moves the victim to act in a manner to reduce the conflict. The attacker can become a “victim,” creating a sense of fellowship with the target, creating a false sense of familiarity, and then using that to drive an action. Social engineers can sell ice to Eskimos and make them proud of their purchase, so they are masters at psychological manipulation.

The attacker may simply ask a question, hoping to immediately obtain the desired information. For basic information that is not considered sensitive, this approach generally works. As an example, an attacker might call and ask who the IT manager is.

The attacker may first attempt to engage the target in conversation and try to evoke sympathy so that the target feels sorry for the individual and is more prone to provide the information. For information that is even slightly sensitive in nature, the request of which could possibly arouse suspicion, this technique may be tried. As an example, an attacker might call and claim to be under some deadline from a supervisor who is upset for some reason. The target, feeling sorry for an alleged fellow worker, may give up the information, thinking they are helping them avoid trouble with the supervisor.

The attacker may appeal to an individual’s ego. As an example, an attacker might call the IT department, claiming to have some sort of problem, and praising them for work they supposedly did to help another worker. After being told how great they are and how much they helped somebody else, they will often be tempted to demonstrate that they can supply the same level of help to another individual. This technique may be used to obtain sensitive information, such as having the target’s password reset.

The second reason that social engineering is successful is that individuals normally seek to avoid confrontation and trouble. If the attacker attempts to intimidate the target, threatening to call the target’s

supervisor because of a lack of help, the target may give in and provide the information to avoid confrontation. This variation on the attack is often successful in organizations that have a strict hierarchical structure. In the military, for example, a lower-ranking individual may be coerced into providing information to an individual claiming to be of higher rank or to be working for another individual higher up in the chain of command. Social engineering may also be accomplished using other means besides

direct contact between the target and the attacker. For example, an attacker might send a forged e-mail with a link to a bogus web site that has been set up to obtain information from the target or convince the target to perform some action. Again, the goal in social engineering is to convince the target to provide information that they normally wouldn’t divulge or to perform some act that they normally would not do. An example of a slightly different attack that is generally still considered a social engineering attack is one in which an attacker replaces the blank deposit slips in a bank’s lobby with ones containing his or her own account number but no name. When an unsuspecting customer uses one of the slips, a teller who is not observant may end up crediting the attacker’s account with the deposit.

Cross Check Types of Social Engineering Chapters 1 and 2 both discussed social engineering. Electronic versions of social engineering have become very common. What are the different types of social engineering (especially electronic versions) that we have discussed?

Obtaining Insider Information An excellent example of social engineering occurred in 1978 when Stanley Mark Rifkin, from Carlsbad, California, stole $10.2 million from the Security Pacific Bank in Los Angeles. Details of the story vary, as Rifkin has never publicly detailed his actions, but a number of facts are known. At the time of the attack, Rifkin was working as a computer consultant for

the bank. While working there, he learned details on how money could easily be transferred to accounts anywhere in the United States. The problem would be to actually obtain the money in the first place. In order to do this, he needed to have access to the electronic funds transfer (EFT) code used by the bank to transfer money to other banks. Using the excuse of checking on the computer equipment inside of the room from which the bank made its transfers, Rifkin was able to observe the code for that day. After leaving the room, he used this information to impersonate a bank officer and ordered the transfer of the $10.2 million. Since he had knowledge of the supposedly secret code, the transfer was made with little fanfare (this amount was well below any level that would trigger any suspicion). Earlier Rifkin had set up a bogus account in a New York bank, using a false name, and he deposited the money into that account. He later transferred the money again to another account in Switzerland under a different name. He then used the money to purchase millions of dollars in diamonds, which he then smuggled back into the United States. The crime might have gone undetected if he had not boasted of his exploits to an individual who was more than happy to turn him in. In 1979, Rifkin was sentenced to eight years in prison. At his trial he attempted to convince the judge that he should be released so he could teach others how to protect their systems against the type of activity he perpetrated. The judge denied this request. The diamonds were ultimately turned over to the bank, which tried to recover its loss by selling them.

Up to this point, social engineering has been discussed in the context of an outsider attempting to gain information about the organization. This does not have to be the case. Insiders may also attempt to gain information they are not authorized to have. In many cases, the insider may be much more successful since they will already have a certain level of information regarding the organization and can therefore better spin a story that may be believable to other employees.

Phishing Phishing (pronounced “fishing”) is a type of social engineering in which

an attacker attempts to obtain sensitive information from a user by masquerading as a trusted entity in an e-mail or instant message sent to a large group of often random users. The attacker attempts to obtain information such as usernames, passwords, credit card numbers, and details about the user’s bank accounts. The message sent often encourages the user to go to a web site that appears to be for a reputable entity such as PayPal or eBay, both of which have frequently been used in phishing attempts. The web site the user actually visits is not owned by the reputable organization, however, and asks the user to supply information that can be used in a later attack. Often the message sent to the user will state that the user’s account has been compromised and will request, for security purposes, the user to enter their account information to verify the details. In another very common example of phishing, the attacker sends a bulk

e-mail, supposedly from a bank, telling the recipients that a security breach has occurred and instructing them to click a link to verify that their account has not been tampered with. If the individual actually clicks the link, they are taken to a site that appears to be owned by the bank but is actually controlled by the attacker. When they supply their account and password for “verification” purposes, they are actually giving it to the attacker.

Phishing is now the most common form of social engineering attack related to computer security. The target may be a computer system and access to the information found on it (such as is the case when the phishing attempt asks for a user ID and password) or the target may be personal information, generally financial, about an individual (in the case of phishing attempts that ask for an individual’s banking information).

The e-mails and web sites generated by the attackers often appear to be legitimate. A few clues, however, can tip off the user that the e-mail might not be what it claims to be. The e-mail may contain grammatical and typographical errors, for example. Organizations that are used in these

phishing attempts (such as eBay and PayPal) are careful about their images and will not send a security-related e-mail to users containing obvious errors. In addition, almost unanimously, organizations tell their users that they will never ask for sensitive information (such as a password or account number) via an e-mail. The URL of the web site that the users are taken to may also provide a clue that the site is not what it appears to be. Despite the increasing media coverage concerning phishing attempts, some Internet users still fall for them, which results in attackers continuing to use this relatively cheap method to gain the information they are seeking.

Another specialized version of phishing is closely related to spear phishing. Again, specific individuals are targeted, but in this case the individuals are important individuals high up in an organization such as the corporate officers. The goal is to go after these “bigger targets,” and thus the term that is used to refer to this form of attack is whaling.

A recent development has been the introduction of a modification to the original phishing attack. Spear phishing is the term that has been created to refer to the special targeting of groups with something in common when launching a phishing attack. By targeting specific groups, the ratio of successful attacks (that is, the number of responses received) to the total number of e-mails or messages sent usually increases because a targeted attack will seem more plausible than a message sent to users randomly. Pharming consists of misdirecting users to fake web sites made to look

official. Using phishing, individuals are targeted one by one by sending out e-mails. To become a victim, the recipient must take an action (for example, respond by providing personal information). In pharming, the user will be directed to the fake web site as a result of activity such as DNS poisoning (an attack that changes URLs in a server’s domain name table) or modification of local host files, which are used to convert URLs to the appropriate IP address. Once at the fake site, the user may supply personal information, believing that they are connected to the legitimate site.

Vishing Vishing is a variation of phishing that uses voice communication technology to obtain the information the attacker is seeking. Vishing takes advantage of the trust that some people place in the telephone network. Users are unaware that attackers can spoof (simulate) calls from legitimate entities using Voice over IP (VoIP) technology. Voice messaging can also be compromised and used in these attempts. Generally, the attackers are hoping to obtain credit card numbers or other information that can be used in identity theft. The user may receive an e-mail asking him or her to call a number that is answered by a potentially compromised voice message system. Users may also receive a recorded message that appears to come from a legitimate entity. In both cases, the user will be encouraged to respond quickly and provide the sensitive information so that access to their account is not blocked. If a user ever receives a message that claims to be from a reputable entity and asks for sensitive information, the user should not provide it but instead should use the Internet or examine a legitimate account statement to find a phone number that can be used to contact the entity. The user can then verify that the message received was legitimate or report the vishing attempt.

Tech Tip

Beware of Vishing Vishing (phishing conducted using voice systems) is generally successful because of the trust that individuals place in the telephone system. With caller ID, people believe they can identify who it is that is calling them. They do not understand that, just like many protocols in the TCP/IP protocol suite, caller ID can be spoofed.

SPAM Though not generally considered a social engineering issue, nor a security issue for that matter, SPAM can, however, be a security concern. SPAM,

as just about everybody knows, is bulk unsolicited e-mail. It can be legitimate in the sense that it has been sent by a company advertising a product or service, but it can also be malicious and could include an attachment that contains malicious software designed to harm your system, or a link to a malicious web site that may attempt to obtain personal information from you. Though not as well known, a variation on SPAM is SPIM, which is basically SPAM delivered via an instant messaging application such as Yahoo! Messenger or AIM. The purpose of hostile SPIM is the same as that of SPAM—the delivery of malicious content or links.

Shoulder Surfing Shoulder surfing does not necessarily involve direct contact with the target, but instead involves the attacker directly observing the individual entering sensitive information on a form, keypad, or keyboard. The attacker may simply look over the shoulder of the user at work, for example, or may set up a camera or use binoculars to view the user entering sensitive data. The attacker can attempt to obtain information such as a personal identification number (PIN) at an automated teller machine (ATM), an access control entry code at a secure gate or door, or a calling card or credit card number. Many locations now use a small shield to surround a keypad so that it is difficult to observe somebody entering information. More sophisticated systems can actually scramble the location of the numbers so that the top row at one time includes the numbers 1, 2, and 3 and the next time 4, 8, and 0. While this makes it a bit slower for the user to enter information, it thwarts an attacker’s attempt to observe what numbers are pressed and enter the same buttons/pattern, since the location of the numbers constantly changes.

A related, somewhat obvious security precaution is that a person should not use the same PIN for all of their different accounts, gate codes, and so on, since an attacker who learns the PIN for one

type of access could then use it for all of the other types of access.

Although methods such as adding shields to block the view or having the pad “scramble” the numbers can help make shoulder surfing more difficult, the best defense is for users to be aware of their surroundings and to not allow individuals to get into a position from which they can observe what the user is entering. The attacker may attempt to increase the chance of successfully

observing the target entering the data by starting a conversation with the target. This provides an excuse for the attacker to be physically closer to the target. Otherwise, the target may be suspicious if the attacker is standing too close. In this sense, shoulder surfing can be considered a social engineering attack.

Reverse Social Engineering A slightly different approach to social engineering is called reverse social engineering. In this technique, the attacker hopes to convince the target to initiate the contact. This obviously differs from the traditional approach, where the target is the one that is contacted. The reason this attack may be successful is that, since the target is the one initiating the contact, attackers may not have to convince the target of their authenticity. The tricky part of this attack is, of course, convincing the target to make that initial contact. Possible methods to accomplish this might include sending out a spoofed e-mail (fake e-mail designed to appear authentic) that claims to be from a reputable source and provides another e-mail address or phone number to call for “tech support,” or posting a notice or creating a bogus web site for a legitimate company that also claims to provide “tech support.” This may be especially successful if timed to coincide with a company’s deployment of a new software or hardware platform. Another potential time to target an organization with this sort of attack is when there is a significant change in the organization itself, such as when two companies merge or a smaller company is acquired by a larger one. During these times, employees are not familiar with the new organization or its procedures,

and amidst the confusion, it is easy to conduct either a social engineering or reverse social engineering attack.

Tech Tip

Be Aware of Reverse Social Engineering Reverse social engineering is not nearly as widely understood as social engineering and is a bit trickier to execute. If the attacker is successful in convincing an individual to make the initial contact, however, the process of convincing them of the authenticity of the attacker is generally much easier than in a social engineering attack.

Hoaxes At first glance, it might seem that a hoax related to security would be considered a nuisance and not a real security issue. This might be the case for some hoaxes, especially those of the urban legend type, but the reality of the situation is that a hoax can be very damaging if it causes users to take some sort of action that weakens security. One real hoax, for example, described a new, highly destructive piece of malicious software. It instructed users to check for the existence of a certain file and to delete it if the file was found. In reality, the file mentioned was an important file used by the operating system, and deleting it caused problems the next time the system was booted. The damage caused by users modifying security settings can be serious. As with other forms of social engineering, training and awareness are the best and first line of defense for both users and administrators. Users should be trained to be suspicious of unusual e-mails and stories and should know who to contact in the organization to verify their validity if they are received. Hoaxes often also advise the user to send it to their friends so they know about the issue as well—and by doing so, they help spread the hoax. Users need to be suspicious of any e-mail telling them to “spread the word.”

Poor Security Practices A significant portion of human-created security problems results from poor security practices. These poor practices may be those of an individual user who is not following established security policies or processes, or they may be caused by a lack of security policies, procedures, or training within the user’s organization.

Password Selection For many years, computer intruders have relied on users’ poor selection of passwords to help the intruders in their attempts to gain unauthorized access to a system or network. If attackers could obtain a list of the users’ names, chances were good they could eventually access the system. Users tend to pick passwords that are easy for them to remember, and what easier password could there be than the same sequence of characters that they use for their user ID? If a system has an account with the username jdoe, an attacker’s reasonable first guess of the account’s password would be jdoe. If this doesn’t work, the attacker would try variations on the same, such as doej, johndoe, johnd, and eodj, all of which would be reasonable possibilities.

Poor password selection is one of the most common of poor security practices, and one of the most dangerous. Numerous studies that have been conducted on password selection have found that, while overall more users are learning to select good passwords, a significant percentage of users still make poor choices. The problem with this, of course, is that a poor password choice can enable an attacker to compromise a computer system or network more easily. Even when users have good passwords, they often resort to another poor security practice—writing the password down in an easily located place, which can also lead to system compromise if an attacker gains physical access to the area.

If the attacker’s attempt to use variations on the username does not yield the correct password, they might simply need more information. Users also frequently pick names of family members, pets, or favorite sports team. If

the user lives in San Antonio, Texas, for example, a possible password might be gospursgo in honor of the city’s professional basketball team. If these attempts don’t work for the attacker, then the attacker might next try hobbies of the user, the name of the user’s favorite make or model of car, or similar pieces of information. The key is that the user often picks something easy for them to remember, which means that the more the attacker knows about the user, the better the chance of discovering the user’s password. In an attempt to complicate the attacker’s job, organizations have

encouraged their users to mix upper- and lowercase characters and to include numbers and special characters in their password. While this does make the password harder to guess, the basic problem still remains: users will pick something that is easy for them to remember. Thus, our user in San Antonio may select the password G0*Spurs*G0, capitalizing three of the letters, inserting a special character twice, and substituting the number zero for the letter O. This makes the password harder to crack, but there are a finite number of variations on the basic gospursgo password, so, while the attacker’s job has been made more difficult, it is still possible to guess the password. Organizations have also instituted additional policies and rules relating

to password selection to further complicate an attacker’s efforts. Organizations, for example, may require users to frequently change their password. This means that if an attacker is able to guess a password, it is only valid for a limited period of time before a new password is selected, after which the attacker is locked out. All is not lost for the attacker, however, since, again, users will select passwords they can remember. For example, password changes often result in a new password that simply incorporates a number at the end of the old one. Thus, our San Antonio user might select G0*Spurs*G1 as the new password, in which case the benefit of forcing password changes on a periodic, or even frequent, basis has been totally lost. It is a good bet that the next password chosen will be G0*Spurs*G2, followed by G0Spurs*G3, and so forth.

Tech Tip

Heartbleed Vulnerability In 2014, a vulnerability in the OpenSSL cryptography was discovered and given the name Heartbleed because it originated in the heartbeat signal employed by the system. This vulnerability resulted in the potential loss of passwords and other sensitive data across multiple platforms and up to a million web servers and related systems. Heartbleed resulted in random data loss from servers, as 64K blocks of memory were exfiltrated from the system. Among the items that may be lost in Heartbleed attacks are user credentials, user IDs, and passwords. The discovery of this vulnerability prompted users to change a massive number of passwords across the Web, as users had no knowledge as to the status of their credentials. One of the common pieces of advice to users was to not reuse passwords between systems. This advice is universally good advice, not just for Heartbleed, but for all systems, all the time.

Another policy or rule governing password selection often adopted by organizations is that passwords must not be written down. This, of course, is difficult to enforce, and thus users will frequently write them down, often as a result of what is referred to as the “password dilemma.” The more difficult we make it for attackers to guess our passwords, and the more frequently we force password changes, the more difficult the passwords are for authorized users to remember and the more likely they are to write them down. Writing them down and putting them in a secure place is one thing, but all too often users will write them on a slip of paper and keep them in their calendar, wallet, or purse. Most security consultants generally agree that if they are given physical access to an office, they will be able to find a password somewhere—the top drawer of a desk, inside of a desk calendar, attached to the underside of the keyboard, or even simply on a yellow “sticky note” attached to the monitor. With the proliferation of computers, networks, and users, the password

dilemma has gotten worse. Today, the average Internet user probably has at least a half dozen different accounts and passwords to remember. Selecting a different password for each account, following the guidelines mentioned previously regarding character selection and frequency of

changes, only aggravates the problem of remembering the passwords. This results in users all too frequently using the same password for all accounts. If a user does this, and then one of the accounts is broken, all other accounts are subsequently also vulnerable to attack.

Know the rules for good password selection. Generally, these are to use eight or more characters in your password, include a combination of upper-and lowercase letters, include at least one number and one special character, do not use a common word, phrase, or name, and choose a password that you can remember so that you do not need to write it down.

The need for good password selection and the protection of passwords also applies to another common feature of today’s electronic world, PINs. Most people have at least one PIN associated with things such as their ATM card or a security code to gain physical access to a room. Again, users will invariably select numbers that are easy to remember. Specific numbers, such as the individual’s birth date, their spouse’s birth date, or the date of some other significant event, are all common numbers to select. Other people will pick patterns that are easy to remember—2580, for example, uses all of the center numbers on a standard numeric pad on a telephone. Attackers know this, and guessing PINs follows the same sort of process that guessing a password does. Password selection is an individual activity, and ensuring that

individuals are making good selections is the realm of the entity’s password policy. To ensure users make appropriate choices, they need to be aware of the issue and their personal role in securing accounts. An effective password policy conveys both the user role and responsibility associated with password usage and does so in a simple enough manner that it can be conveyed via screen notes during mandated password change events.

Shoulder Surfing

As discussed earlier, shoulder surfing does not involve direct contact with the user, but instead involves the attacker directly observing the target entering sensitive information on a form, keypad, or keyboard. The attacker may simply look over the shoulder of the user at work, watching as a coworker enters their password. Although defensive methods can help make shoulder surfing more difficult, the best defense is for a user to be aware of their surroundings and to not allow individuals to get into a position from which they can observe what the user is entering. A related security comment can be made at this point: a person should not use the same PIN for all of their different accounts, gate codes, and so on, since an attacker who learns the PIN for one could then use it for all the others.

Piggybacking People are often in a hurry and will frequently not follow good physical security practices and procedures. Attackers know this and may attempt to exploit this characteristic in human behavior. Tailgating or piggybacking is the simple tactic of following closely behind a person who has just used their own access card or PIN to gain physical access to a room or building. An attacker can thus gain access to the facility without having to know the access code or having to acquire an access card. It is similar to shoulder surfing in that it relies on the attacker taking advantage of an authorized user not following security procedures. Frequently the attacker may even start a conversation with the target before reaching the door so that the user may be more comfortable with allowing the individual in without challenging them. In this sense piggybacking is related to social engineering attacks. Both the piggybacking and shoulder surfing attack techniques can be easily countered by using simple procedures to ensure nobody follows you too closely or is in a position to observe your actions. Both techniques rely on the poor security practices of an authorized user to be successful. A more sophisticated countermeasure to piggybacking is a “man trap,” which utilizes two doors to gain access to the facility. The second door does not open until the first one is closed and is spaced close enough to the first that an enclosure is formed that only allows one

individual through at a time.

Dumpster Diving As mentioned earlier, attackers need a certain amount of information before launching their attack. One common place to find this information, if the attacker is in the vicinity of the target, is the target’s trash. The attacker might find little bits of information that could be useful for an attack. This process of going through a target’s trash in hopes of finding valuable information that might be used in a penetration attempt is known in the computer community as dumpster diving. The tactic is not, however, unique to the computer community; it has been used for many years by others, such as identity thieves, private investigators, and law enforcement personnel, to obtain information about an individual or organization. If the attackers are very lucky, and the target’s security procedures are very poor, they may actually find user IDs and passwords. As mentioned in the discussion on passwords, users sometimes write their password down. If, when the password is changed, they discard the paper the old password was written on without shredding it, the lucky dumpster diver can gain a valuable clue. Even if the attacker isn’t lucky enough to obtain a password directly, he undoubtedly will find employee names, from which it’s not hard to determine user IDs, as discussed earlier. Finally, the attacker may gather a variety of information that can be useful in a social engineering attack. In most locations, trash is no longer considered private property after it has been discarded (and even where dumpster diving is illegal, little enforcement occurs). An organization should have policies about discarding materials. Sensitive information should be shredded and the organization should consider securing the trash receptacle so that individuals can’t forage through it. People should also consider shredding personal or sensitive information that they wish to discard in their own trash. A reasonable quality shredder is inexpensive and well worth the price when compared with the potential loss that could occur as a result of identity theft.

Try This! Diving into Your Dumpster The amount of useful information that users throw away in unsecured trash receptacles often amazes security professionals. Hackers know that they can often find manuals, network diagrams, and even user IDs and passwords by rummaging through dumpsters. After coordinating this with your security office, try seeing what you can find that individuals in your organization have discarded (assuming that there is no shredding policy) by either going through your organization’s dumpsters or just through the office trash receptacles. What useful information did you find? Is there an obvious suggestion that you might make to enhance the security of your organization?

Installing Unauthorized Hardware and Software Organizations should have a policy that restricts the ability of normal users to install software and new hardware on their systems. A common example is a user installing unauthorized communication software and a modem to allow them to connect to their machine at work via a modem from their home. Another common example is a user installing a wireless access point so that they can access the organization’s network from many different areas. In these examples, the user has set up a backdoor into the network, circumventing all the other security mechanisms in place. The term “rogue modem” or “rogue access point” may be used to describe these two cases. A backdoor is an avenue that can be used to access a system while circumventing normal security mechanisms and can often be used to install additional executable files that can lead to more ways to access the compromised system. Security professionals can use widely available tools to scan their own systems periodically for either of these rogue devices to ensure that users haven’t created a backdoor.

It has already been mentioned that gaining physical access to a computer system or network often guarantees an attacker success in penetrating the system or the network it is connected to. At the same time, there may be a number of individuals who have access to a facility but are not

authorized to access the information the systems store and process. We become complacent to the access these individuals have because they often quietly go about their job so as to not draw attention to themselves and to minimize the impact on the operation of the organization. They may also be overlooked because their job does not impact the core function of the organization. A prime example of this is the custodial staff. Becoming complacent about these individuals and not paying attention to what they may have access to, however, could be a big mistake, and users should not believe that everybody who has physical access to the organization has the same level of concern for or interest in the welfare of the organization.

Another common example of unauthorized software that users install on their systems is games. Unfortunately, not all games come in shrink- wrapped packages. Numerous small games can be downloaded from the Internet. The problem with this is that users don’t always know where the software originally came from and what may be hidden inside it. Many individuals have unwittingly installed what seemed to be an innocuous game, only to have downloaded a piece of malicious code capable of many things, including opening a backdoor that allows attackers to connect to, and control, the system from across the Internet. Because of these potential hazards, many organizations do not allow

their users to load software or install new hardware without the knowledge and assistance of administrators. Many organizations also screen, and occasionally intercept, e-mail messages with links or attachments that are sent to users. This helps prevent users from, say, unwittingly executing a hostile program that was sent as part of a worm or virus. Consequently, many organizations have their mail servers strip off executable attachments to e-mail so that users can’t accidentally cause a security problem.

Data Handling Understanding the responsibilities of proper data handling associated with one’s job is an important training topic. Information can be deceptive in that it is not directly tangible, and people tend to develop bad habits around other job measures … at the expense of security. Employees require training in how to recognize the data classification and handling requirements of the data they are using, and they need to learn how to

follow the proper handling processes. If certain data elements require special handling because of contracts, laws, or regulations, there is typically a training clause associated with this requirement. Personnel assigned to these tasks should be specifically trained with regard to the security requirements. The spirit of the training clause is you get what you train, and if security over specific data types is a requirement, then it should be trained. This same principle holds for corporate data-handling responsibilities; you get the behaviors you train and reward.

Physical Access by Non-Employees As has been mentioned, if an attacker can gain physical access to a facility, chances are very good that the attacker can obtain enough information to penetrate computer systems and networks. Many organizations require employees to wear identification badges when at work. This is an easy method to quickly spot who has permission to have physical access to the organization and who does not. While this method is easy to implement and can be a significant deterrent to unauthorized individuals, it also requires that employees actively challenge individuals who are not wearing the required identification badge. This is one area where organizations fail. Combine an attacker who slips in by piggybacking off of an authorized individual and an environment where employees have not been encouraged to challenge individuals without appropriate credentials and you have a situation where you might as well not have any badges in the first place. Organizations also frequently become complacent when faced with what appears to be a legitimate reason to access the facility, such as when an individual shows up with a warm pizza claiming it was ordered by an employee. It has often been stated by security consultants that it is amazing what you can obtain access to with a pizza box or a vase of flowers.

Preventing access to information is also important in the work area. Firms with sensitive

information should have a “clean desk policy” specifying that sensitive information is not left unsecured in the work area when the worker is not present to act as custodian.

Another aspect that must be considered is personnel who have legitimate access to a facility but also have intent to steal intellectual property or otherwise exploit the organization. Physical access provides an easy opportunity for individuals to look for the occasional piece of critical information carelessly left out. With the proliferation of devices such as cell phones with built-in cameras, an individual could easily photograph information without it being obvious to employees. Contractors, consultants, and partners frequently not only have physical access to the facility but may also have network access. Other individuals who typically have unrestricted access to the facility when no one is around are nighttime custodial crewmembers and security guards. Such positions are often contracted out. As a result, hackers have been known to take temporary custodial jobs simply to gain access to facilities.

Clean Desk Policies Preventing access to information is also important in the work area. Firms with sensitive information should have a “clean desk policy” specifying that sensitive information must not be left unsecured in the work area when the worker is not present to act as custodian. Even leaving the desk area and going to the bathroom can leave information exposed and subject to compromise. The clean desk policy should identify and prohibit things that are not obvious upon first glance, such as passwords on sticky notes under keyboards and mouse pads or in unsecured desk drawers.

People as a Security Tool An interesting paradox when speaking of social engineering attacks is that people are not only the biggest problem and security risk but also the best tool in defending against a social engineering attack. The first step a company should take to fight potential social engineering attacks is to

create the policies and procedures that establish the roles and responsibilities for not only security administrators but for all users. What is it that management expects, security-wise, from all employees? What is it that the organization is trying to protect, and what mechanisms are important for that protection?

Per the 2014 Verizon Data Breach Investigation Report, introduced in Chapter 1, hacks were discovered more often by internal employees than by outsiders. This means that trained users can be an important part of a security plan.

Security Awareness Probably the single most effective method to counter potential social engineering attacks, after establishment of the organization’s security goals and policies, is an active security awareness program. The extent of the training will vary depending on the organization’s environment and the level of threat, but initial employee training on social engineering at the time a person is hired is important, as well as periodic refresher training. An important element that should be stressed in training about social

engineering is the type of information that the organization considers sensitive and which may be the target of a social engineering attack. There are undoubtedly signs that the organization could point to as indicative of an attacker attempting to gain access to sensitive corporate information. All employees should be aware of these indicators. The scope of information that an attacker may ask for is very large, and many questions attackers pose might also be legitimate in another context (asking for someone’s phone number, for example). Employees should be taught to be cautious about revealing personal information and should especially be alert for questions regarding account information, personally identifiable information, or passwords.

Try This! Security Awareness Programs A strong security education and awareness training program can go a long way toward reducing the chance that a social engineering attack will be successful. Awareness programs and campaigns, which might include seminars, videos, posters, newsletters, and similar materials, are also fairly easy to implement and not very costly. There is no reason for an organization to not have an awareness program in place. A lot of information and ideas are available on the Internet. See what you can find that might be usable for your organization that you can obtain at no charge from various organizations on the Internet. (Tip: Check organizations such as NIST and NSA, which have developed numerous security documents and guidelines.)

As a final note on user responsibilities, corporate security officers must cultivate an environment of trust in their office, as well as an understanding of the importance of security. If users feel that security personnel are only there to make their life difficult or to dredge up information that will result in an employee’s termination, the atmosphere will quickly turn adversarial and be transformed into an “us versus them” situation. Security personnel need the help of all users and should strive to cultivate a team environment in which users, when faced with a questionable situation, will not hesitate to call the security office. In situations like this, security offices should remember the old adage of “don’t shoot the messenger.”

Security Policy Training and Procedures People in an organization play a significant role in the security posture of the organization, As such, training is important as it can provide the basis for awareness of issues such as social engineering and desired employee security habits. These are detailed in Chapter 2.

Chapter 4 Review

Chapter Summary After reading this chapter and completing the exercises, you should understand the following regarding the role people can play in security.

Define basic terminology associated with social engineering

Social engineering is a technique in which the attacker uses various deceptive practices to convince the targeted person to divulge information they normally would not divulge, or to convince the target to do something they normally wouldn’t do.

In reverse social engineering, the attacker hopes to convince the target to initiate contact.

Describe steps organizations can take to improve their security

Organizations should have a policy that restricts the ability of normal users to install new software and hardware on their systems.

Contractors, consultants, and partners may frequently have not only physical access to the facility but also network access. Other groups that are given unrestricted, and unobserved, access to a facility are nighttime custodial crewmembers and security guards. Both are potential security problems and organizations should take steps to limit these individuals’ access.

The single most effective method to counter potential social engineering attacks, after establishing the organization’s security goals and policies, is an active security awareness program.

Describe common user actions that may put an organization’s information at risk

No matter how advanced security technology is, it will ultimately be deployed in an environment where the human element may be its greatest weakness.

Attackers know that employees are frequently very busy and don’t stop to think about security. They may attempt to exploit this work characteristic through piggybacking or shoulder surfing.

Recognize methods attackers may use to gain information about an organization

For many years computer intruders have relied on users’ poor selection of passwords to help the intruders in their attempts to gain unauthorized access to a system or network.

One common way to find useful information (if the attacker is in the vicinity of the target, such as a company office) is to go through the target’s trash looking for bits of information that could be useful to a penetration attempt.

Determine ways in which users can aid instead of detract from security

An interesting paradox of social engineering attacks is that people are not only the biggest problem and security risk but also the best line of defense against a social engineering attack.

A significant portion of employee-created security problems arise from poor security practices.

Users should always be on the watch for attempts by individuals to gain information about the organization and should report suspicious activity to their employer.

Recognize the role training and awareness plays in assisting the people side of security

Individual users can enhance security of a system through proper execution of their individual actions and responsibilities.

Training and awareness programs can reinforce user knowledge of

desired actions.

Key Terms backdoor (82) dumpster diving (81) phishing (75) piggybacking (80) reverse social engineering (77) shoulder surfing (76) social engineering (73) SPAM (76) tailgating (80) vishing (76)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. A _______________ is an avenue that can be used to access a system while circumventing normal security mechanisms.

2. _______________ is a procedure in which attackers position themselves in such a way as to be able to observe an authorized user entering the correct access code.

3. The process of going through a target’s trash searching for information that can be used in an attack, or to gain knowledge about a system or network, is known as _______________.

4. _______________ is the simple tactic of following closely behind a person who has just used their access card or PIN to gain physical access to a room or building.

5. In _______________, the attacker hopes to convince the target to initiate contact.

6. _______________ is a variation of _______________ that uses voice communication technology to obtain the information the attacker is seeking.

Multiple-Choice Quiz 1. Which of the following is considered a good practice for password

security?

A. Using a combination of upper- and lowercase characters, a number, and a special character in the password itself

B. Not writing the password down

C. Changing the password on a regular basis

D. All of the above

2. The password dilemma refers to the fact that: A. Passwords that are easy for users to remember are also easy for

attackers to guess.

B. The more difficult we make it for attackers to guess our passwords, and the more frequently we force password changes, the more difficult the passwords are for authorized users to remember and the more likely they are to write them down.

C. Users will invariably attempt to select passwords that are words they can remember. This means they may select things closely associated with them, such as their spouse’s or child’s name, a beloved sports team, or a favorite model of car.

D. Passwords assigned by administrators are usually better and

more secure, but are often harder for users to remember.

3. The simple tactic of following closely behind a person who has just used their own access card or PIN to gain physical access to a room or building is called:

A. Shoulder surfing

B. Tagging-along

C. Piggybacking

D. Access drafting

4. The process of going through a target’s trash in hopes of finding valuable information that might be used in a penetration attempt is known as:

A. Dumpster diving

B. Trash trolling

C. Garbage gathering

D. Refuse rolling

5. Which of the following is a type of social engineering attack in which an attacker attempts to obtain sensitive information from a user by masquerading as a trusted entity in an e-mail?

A. SPAM

B. SPIM

C. Phishing

D. Vishing

6. Reverse social engineering involves: A. Contacting the target, eliciting some sensitive information, and

convincing them that nothing out of the ordinary has occurred

B. Contacting the target in an attempt to obtain information that can be used in a second attempt with a different individual

C. An individual lower in the chain of command convincing somebody at a higher level to divulge information that the attacker is not authorized to have

D. An attacker attempting to somehow convince the target to initiate contact in order to avoid questions about authenticity

7. The reason for not allowing users to install new hardware or software without the knowledge of security administrators is:

A. They may not complete the installation correctly and the administrator will have to do more work, taking them away from more important security tasks.

B. They may inadvertently install more than just the hardware or software; they may accidentally install a backdoor into the network.

C. They may not have paid for it and thus may be exposing the organization to civil penalties.

D. Unauthorized hardware and software are usually for leisure purposes and will distract employees from the job they were hired to perform.

8. Once an organization’s security policies have been established, the single most effective method of countering potential social engineering attacks is:

A. An active security awareness program

B. A separate physical access control mechanism for each department in the organization

C. Frequent testing of both the organization’s physical security procedures and employee telephone practices

D. Implementing access control cards and the wearing of security identification badges

9. Which of the following types of attacks utilizes instant messaging services?

A. SPAM

B. SPIM

C. Phishing

D. Vishing

10. In what way are PINs similar to passwords? A. Users will normally pick a PIN that is easy to remember, such

as a date or specific pattern.

B. Attackers know common PINs and will try to use them or will attempt to learn more about the user in order to make an educated guess as to what their PIN might be.

C. Users may write them down to remember them.

D. All of the above are true.

Essay Quiz 1. Explain the difference between social engineering and reverse social

engineering.

2. Discuss how a security-related hoax might become a security issue. 3. How might shoulder surfing be a threat in your school or work

environment? What can be done to make this sort of activity more difficult?

4. For an environment familiar to you (such as work or school), describe the different non-employees who may have access to

facilities that could contain sensitive information.

5. Describe some of the user security responsibilities that you feel are most important for users to remember.

Lab Projects

• Lab Project 4.1 If possible at either your place of employment or your school, attempt to determine how easy it would be to perform dumpster diving to gain access to information at the site. Are trash receptacles easy to gain access to? Are documents shredded before being discarded? Are areas where trash is stored easily accessible?

• Lab Project 4.2 Perform a search on the Web for articles and stories about social engineering attacks or reverse social engineering attacks. Choose and read five or six articles. How many of the attacks were successful? How many failed and why? How could those that may have initially succeeded been prevented?

• Lab Project 4.3 Similar to Lab Project 4.2, perform a search on the Web for articles and stories about phishing attacks. Choose and read five or six articles. How many of the attacks were successful? How many failed and why? How might the successful attacks have been mitigated or successfully accomplished?

chapter 5 Cryptography

If you are designing cryptosystems, you’ve got to think about long-term applications. You’ve got to try to figure out how to build something that is secure against technology in the next century

C

that you cannot even imagine.

—WHITFIELD DIFFIE

In this chapter, you will learn how to

Understand the fundamentals of cryptography

Identify and describe the three types of cryptography

List and describe current cryptographic algorithms

Explain how cryptography is applied for security

ryptography is the science of encrypting, or hiding, information— something people have sought to do since they began using language. Although language allowed people to communicate with one another,

those in power attempted to hide information by controlling who was taught to read and write. Eventually, more complicated methods of concealing information by shifting letters around to make the text unreadable were developed. These complicated methods are cryptographic algorithms, also known as ciphers. The word cipher comes from the Arabic word sifr, meaning empty or zero. When material, called plaintext, needs to be protected from

unauthorized interception or alteration, it is encrypted into ciphertext. This is done using an algorithm and a key, and the rise of digital computers has provided a wide array of algorithms and increasingly complex keys. The choice of specific algorithm depends on several factors, and they will be examined in this chapter. Cryptanalysis, the process of analyzing available information in an

attempt to return the encrypted message to its original form, required advances in computer technology for complex encryption methods. The birth of the computer made it possible to easily execute the calculations required by more complex encryption algorithms. Today, the computer almost exclusively powers how encryption is performed. Computer technology has also aided cryptanalysis, allowing new methods to be

developed, such as linear and differential cryptanalysis. Differential cryptanalysis is done by comparing the input plaintext to the output ciphertext to try and determine the key used to encrypt the information. Linear cryptanalysis is similar in that it uses both plaintext and ciphertext, but it puts the plaintext through a simplified cipher to try and deduce what the key is likely to be in the full version of the cipher.

Cryptography in Practice While cryptography may be a science, it performs critical functions in the enabling of trust across computer networks in business and other functions. Before we dig deep into the technical nature of cryptographic practices, an overview of current capabilities is useful. Examining cryptography from a high level, there are several relevant points today. Cryptography has been a long-running event of advances both on the

side of cryptography and the side of breaking it via analysis. With the advent of digital cryptography, the advantage has clearly swung to the side of cryptography. Modern computers have also increased the need for, and lowered the cost of employing, cryptography to secure information. In the past, the effectiveness rested in the secrecy of the algorithm, but with modern digital cryptography, the strength is based on sheer complexity. The power of networks and modern algorithms has also been employed to manage automatic key management.

Cryptography is much more than encryption. Cryptographic methods enable data protection, data hiding, integrity checks, nonrepudiation services, policy enforcement, key management and exchange, and many more elements used in modern computing. If you used the Web today, odds are you used cryptography without even knowing it.

Cryptography has many uses besides just enabling confidentiality in communication channels. Cryptographic functions are used in a wide

range of applications, including, but not limited to, hiding data, resisting forgery, resisting unauthorized change, resisting repudiation, policy enforcement, and key exchanges. In spite of the strengths of modern cryptography, it still fails due to other issues; known plaintext attacks, poorly protected keys, and repeated passphrases are examples of how strong cryptography is rendered weak via implementation mistakes. Modern cryptographic algorithms are far stronger than needed given the

state of cryptanalysis. The weaknesses in cryptosystems come from the system surrounding the algorithm, implementation, and operationalization details. Adi Shamir, the S in RSA, states it clearly: “Attackers do not break crypto; they bypass it.” Over time, weaknesses and errors, as well as shortcuts, are found in

algorithms. When an algorithm is reported as broken, the term “broken” can have many meanings. This could mean that the algorithm is of no further use, or it could mean that it has weaknesses that may someday be employed to break it, or anything between these extremes. As all methods can be broken with brute force, one question is how much effort is required, at what cost, when compared to the value of the asset under protection. When examining the strength of a cryptosystem, it is worth examining

the following types of levels of protection:

1. The mechanism is no longer useful for any purpose. 2. The cost of recovering the clear text without benefit of the key has fallen to a low level.

3. The cost has fallen to equal to or less than the value of the data or the next least cost attack.

4. The cost has fallen to within several orders of magnitudes of the cost of encryption or the value of the data.

5. The elapsed time of attack has fallen to within magnitudes of the life of the data, regardless of the cost thereof.

6. The cost has fallen to less than the cost of a brute-force attack against the key.

7. Someone has recovered one key or one message.

This list of conditions is a descending list of risks/benefits. Conditions 6 and 7 are regular occurrences in cryptographic systems, and generally not worth worrying about at all. In fact, it is not until the fourth point that one has to have real concerns. With all this said, most organizations consider replacement between 5 and 6. If any of the first three are positive, the organization seriously needs to consider changing their cryptographic methods.

Fundamental Methods Modern cryptographic operations are performed using both an algorithm and a key. The choice of algorithm depends on the type of cryptographic operation that is desired. The subsequent choice of key is then tied to the specific algorithm. Cryptographic operations include encryption (for the protection of confidentiality), hashing (for the protection of integrity), digital signatures (to manage nonrepudiation), and a bevy of specialty operations such as key exchanges. The methods used to encrypt information are based on two separate

operations, substitution and transposition. Substitution is the replacement of an item with a different item. Transposition is the changing of the order of items. Pig Latin, a child’s cipher, employs both operations in simplistic form and is thus easy to decipher. These operations can be done on words, characters, and, in the digital world, bits. What makes a system secure is the complexity of the changes employed. To make a system reversible (so you can reliably decrypt it), there needs to be a basis for the pattern of changes. Historical ciphers used relatively simple patterns, and ones that required significant knowledge (at the time) to break. Modern cryptography is built around complex mathematical functions.

These functions have specific properties that make them resistant to

reversing or solving by means other than the application of the algorithm and key.

Assurance is a specific term in security that means that something is not only true but can be proven to be so to some specific level of certainty.

While the mathematical specifics of these operations can be very complex and are beyond the scope of this level of material, the knowledge to properly employ them is not. Cryptographic operations are characterized by the quantity and type of data, as well as the level and type of protection sought. Integrity protection operations are characterized by the level of assurance desired. Data can be characterized by its state: data in transit, data at rest, or data in use. It is also characterized in how it is used, either in block form or stream form.

Comparative Strengths and Performance of Algorithms There are several factors that play a role in determining the strength of a cryptographic algorithm. First and most obvious is the size of the key and the resulting keyspace. The keyspace is defined as a set of every possible key value. One method of attack is to simply try all of the possible keys in a brute-force attack. The other factor is referred to as work factor, which is a subjective measurement of the time and effort needed to perform operations. If the work factor is low, then the rate at which keys can be tested is high, meaning that larger keyspaces are needed. Work factor also plays a role in protecting systems such as password hashes, where having a higher work factor can be part of the security mechanism.

Tech Tip

Keyspace Comparisons Because the keyspace is a numeric value, it is very important to ensure that comparisons are done using similar key types. Comparing a key made of 1 bit (2 possible values) and a key made of 1 letter (26 possible values) would not yield accurate results. Fortunately, the widespread use of computers has made almost all algorithms state their keyspace values in terms of bits.

A larger keyspace allows the use of keys of greater complexity, and therefore more security, assuming the algorithm is well designed. It is easy to see how key complexity affects an algorithm when you look at some of the encryption algorithms that have been broken. The Data Encryption Standard (DES) uses a 56-bit key, allowing 72,000,000,000,000,000 possible values, but it has been broken by modern computers. The modern implementation of DES, Triple DES (3DES), uses three 56-bit keys, for a total key length of 168 bits (although for technical reasons the effective key length is 112 bits), or 340,000,000,000,000,000,000,000,000,000,000,000,000 possible values. When an algorithm lists a certain number of bits as a key, it is defining

the keyspace. Some algorithms have key lengths of 8192 bits or more, resulting in very large keyspaces, even by digital computer standards. Modern computers have also challenged work factor elements as

algorithms can be rendered very quickly by specialized hardware such as high-end graphic chips. To defeat this, many algorithms have repeated cycles to add to the work and reduce the ability to parallelize operations inside processor chips. This is done to increase the inefficiency of a calculation, but in a manner that still results in suitable performance when given the key and still complicates matters when done in a brute-force manner with all keys.

Historical Perspectives

Cryptography is as old as secrets. Humans have been designing secret communication systems for as long they’ve needed to keep communication private. The Spartans of ancient Greece would write on a ribbon wrapped around a cylinder with a specific diameter (called a scytale). When the ribbon was unwrapped, it revealed a strange string of letters. The message could be read only when the ribbon was wrapped around the same diameter cylinder. This is an example of a transposition cipher, where the same letters are used but the order is changed. In all these cipher systems, the unencrypted input text is known as plaintext and the encrypted output is known as ciphertext.

Substitution Ciphers The Romans typically used a different method known as a shift cipher. In this case, one letter of the alphabet is shifted a set number of places in the alphabet for another letter. A common modern-day example of this is the ROT13 cipher, in which every letter is rotated 13 positions in the alphabet: n is written instead of a, o instead of b, and so on. These types of ciphers are commonly encoded on an alphabet wheel, as shown in Figure 5.1.

• Figure 5.1 Any shift cipher can easily be encoded and decoded on a wheel of two pieces of paper with the alphabet set as a ring; by moving one circle the specified number in the shift, you can translate the characters.

These ciphers were simple to use and also simple to break. Because hiding information was still important, more advanced transposition and substitution ciphers were required. As systems and technology became more complex, ciphers were frequently automated by some mechanical or electromechanical device. A famous example of a relatively modern encryption machine is the German Enigma machine from World War II (see Figure 5.2). This machine used a complex series of substitutions to perform encryption, and interestingly enough it gave rise to extensive research in computers.

• Figure 5.2 One of the surviving German Enigma machines

Caesar’s cipher uses an algorithm and a key: the algorithm specifies that you offset the alphabet either to the right (forward) or to the left (backward), and the key specifies how many letters the offset should be. For example, if the algorithm specifies offsetting the alphabet to the right,

and the key is 3, the cipher substitutes an alphabetic letter three to the right for the real letter, so d is used to represent a, f represents c, and so on. In this example, both the algorithm and key are simple, allowing for easy cryptanalysis of the cipher and easy recovery of the plaintext message. The ease with which shift ciphers were broken led to the development of

substitution ciphers, which were popular in Elizabethan England (roughly the second half of the 16th century) and more complex than shift ciphers. Substitution ciphers work on the principle of substituting a different letter for every letter: a becomes g, b becomes d, and so on. This system permits 26 possible values for every letter in the message, making the cipher many times more complex than a standard shift cipher. Simple analysis of the cipher could be performed to retrieve the key, however. By looking for common letters such as e and patterns found in words such as ing, you can determine which cipher letter corresponds to which plaintext letter. The examination of ciphertext for frequent letters is known as frequency analysis. Making educated guesses about words will eventually allow you to determine the system’s key value (see Figure 5.3).

• Figure 5.3 Making educated guesses is much like playing hangman— correct guesses can lead to more or all of the key being revealed.

To correct this problem, more complexity had to be added to the system. The Vigenère cipher works as a polyalphabetic substitution cipher that depends on a password. This is done by setting up a substitution table like this one:

Then the password is matched up to the text it is meant to encipher. If the password is not long enough, the password is repeated until one character of the password is matched up with each character of the plaintext. For example, if the plaintext is Sample Message and the password is password, the resulting match is

SAMPLEMESSAGE PASSWORDPASSW

The cipher letter is determined by use of the grid, matching the plaintext character’s row with the password character’s column, resulting in a single ciphertext character where the two meet. Consider the first letters S and P: when plugged into the grid they output a ciphertext character of H. This process is repeated for every letter of the message. Once the rest of the letters are processed, the output is HAEHHSDHHSSYA. In this example, the key in the encryption system is the password. The

example also illustrates that an algorithm can be simple and still provide

strong security. If someone knows about the table, they can determine how the encryption was performed, but they still will not know the key to decrypting the message. The more complex the key, the greater the security of the system. The

Vigenère cipher system and systems like it make the algorithms rather simple but the key rather complex, with the best keys comprising very long and very random data. Key complexity is achieved by giving the key a large number of possible values.

Try This! Vigenère Cipher Make a simple message that’s about two sentences long, and then choose two passwords, one that’s short and one that’s long. Then, using the substitution table presented in this section, perform simple encryption on the message. Compare the two ciphertexts; since you have the plaintext and the ciphertext, you should be able to see a pattern of matching characters. Knowing the algorithm used, see if you can determine the key used to encrypt the message.

One-time Pads One-time pads are an interesting form of encryption in that they theoretically are perfect and unbreakable. The key is the same size or larger than the material being encrypted. The plaintext is XOR’ed against the key producing the ciphertext. What makes the one-time pad “perfect” is the size of the key. If you use a keyspace full of keys, you will decrypt every possible message of the same length as the original, with no way to discriminate which one is correct. This makes a one-time pad unable to be broken by even brute-force methods, provided that the key is not reused. This makes a one-time pad less than practical for any mass use.

One-time pads are examples of perfect ciphers from a mathematical point of view. But when put

into practice, the implementation creates weaknesses that result in less than perfect security. This is an important reminder that perfect ciphers from a mathematical point of view do not create perfect security in practice because of the limitations associated with implementation.

Algorithms Every current encryption scheme is based upon an algorithm, a step-by- step, recursive computational procedure for solving a problem in a finite number of steps. The cryptographic algorithm—what is commonly called the encryption algorithm or cipher—is made up of mathematical steps for encrypting and decrypting information. The following illustration shows a diagram of the encryption and decryption process and its parts. There are three types of encryption algorithms commonly used: hashing, symmetric, and asymmetric. Hashing is a very special type of encryption algorithm that takes an input and mathematically reduces it to a unique number known as a hash, which is not reversible. Symmetric algorithms are also known as shared secret algorithms, as the same key is used for encryption and decryption. Finally, asymmetric algorithms use a very different process employing two keys, a public key and a private key, making up what is known as a key pair.

The best algorithms are always public algorithms that have been published for peer review by other cryptographic and mathematical experts. Publication is important, as any flaws in the system can be

revealed by others before actual use of the system. This process greatly encourages the use of proven technologies. Several proprietary algorithms have been reverse-engineered, exposing the confidential data the algorithms try to protect. Examples of this include the decryption of Nikon’s proprietary RAW format, white-balance encryption, and the cracking of the ExxonMobil Speedpass RFID encryption. The use of a proprietary system can actually be less secure than using a published system. Whereas proprietary systems are not made available to be tested by potential crackers, public systems are made public for precisely this purpose.

One of the most common cryptographic failures is the creation of your own encryption scheme. Rolling your own cryptography, whether in creating algorithms or implementation of existing algorithms yourself, is a recipe for failure. Always use approved algorithms and always use approved crypto libraries to implement.

A system that maintains its security after public testing can be reasonably trusted to be secure. A public algorithm can be more secure because good systems rely on the encryption key to provide security, not the algorithm itself. The actual steps for encrypting data can be published, because without the key, the protected information cannot be accessed (see Figure 5.4).

• Figure 5.4 While everyone knows how to use a knob to open a door, without the key to unlock the knob, that knowledge is useless.

A key is a special piece of data used in both the encryption and decryption processes. The algorithms stay the same in every implementation, but a different key is used for each, which ensures that even if someone knows the algorithm you use to protect your data, he cannot break your security.

Tech Tip

XOR A popular function in cryptography is eXclusive OR (XOR), which is a bitwise function applied to data. When you apply a key to data using XOR, then a second application undoes the first operation. This makes for speedy encryption/decryption, but makes the system totally dependent upon the secrecy of the key. A hard-coded key in a program will be discovered, making this a weak security mechanism in most cases.

Comparing the strength of two different algorithms can be mathematically very challenging; fortunately for the layperson, there is a rough guide. Most current algorithms are listed with their key size in bits. Unless a specific algorithm has been shown to be flawed, in general, the greater number of bits will yield a more secure system. This works well for a given algorithm, but is meaningless to compare different algorithms. The good news is that most modern cryptography is more than strong enough for all but technical uses, and for those uses experts can determine appropriate algorithms and key lengths to provide the necessary protections.

Tech Tip

Man-in-the-Middle Attack A man-in-the-middle attack is designed to defeat proper key exchange by intercepting the remote party’s key and replacing it with the attacker’s key in both directions. If done properly, only the attacker knows that the encrypted traffic is not secure and the encrypted traffic can be read by the attacker.

Key Management Because the security of the algorithms relies on the key, key management is of critical concern. Key management includes anything having to do with the exchange, storage, safeguarding, and revocation of keys. It is most commonly associated with asymmetric encryption, since asymmetric encryption uses both public and private keys. To be used properly for

authentication, a key must be current and verified. If you have an old or compromised key, you need a way to check to see that the key has been revoked. Key management is also important for symmetric encryption, because

symmetric encryption relies on both parties having the same key for the algorithm to work. Since these parties are usually physically separate, key management is critical to ensure keys are shared and exchanged easily. They must also be securely stored to provide appropriate confidentiality of the encrypted information. There are many different approaches to secure storage of keys, such as putting them on a USB flash drive or smart card. While keys can be stored in many different ways, new PC hardware often includes the Trusted Platform Module (TPM), which provides a hardware- based key storage location that is used by many applications. (More specific information about the management of keys is provided later in this chapter and in Chapter 6.)

Random Numbers Many digital cryptographic algorithms have a need for a random number to act as a seed and provide true randomness. One of the strengths of computers is that they can do a task over and over again in the exact same manner—no noise or randomness. This is great for most tasks, but in generating a random sequence of values, it presents challenges. Software libraries have pseudo-random generators, functions that produce a series of numbers that statistically appear random. But these random number generators are deterministic in that, given the sequence, you can calculate future values. This makes them inappropriate for use in cryptographic situations. The level or amount of randomness is referred to as entropy. Entropy is

the measure of uncertainty associated with a series of values. Perfect entropy equates to complete randomness, such that given any string of bits, there is no computation to improve guessing the next bit in the sequence. A simple “measure” of entropy is in bits, where the bits are the power of 2

that represents the number of choices. So if there are 2048 options, then this would represent 11 bits of entropy. In this fashion, one can calculate the entropy of passwords and measure how “hard they are to guess.”

Tech Tip

Randomness Issues The importance of proper random number generation in cryptosystems cannot be underestimated. Recent reports by the Guardian and the New York Times assert that the U.S. National Security Agency (NSA) has put a backdoor into the Cryptographically Secure Random Number Generator (CSPRNG) algorithms described in NIST SP 800-90A, particularly the Dual_EC_DRBG algorithm. Further allegations are that the NSA paid RSA $10 million to use the resulting standard in its product line.

To resolve the problem of appropriate randomness, there are systems to create cryptographic random numbers. The level of complexity of the system is dependent upon the level of pure randomness needed. For some functions, such as master keys, the only true solution is a hardware-based random number generator that can use physical properties to derive entropy. In other, less demanding cases, a cryptographic library call can provide the necessary entropy. While the theoretical strength of the cryptosystem depends on the algorithm, the strength of the implementation in practice can depend on issues such as the key. This is a very important issue and mistakes made in implementation can invalidate even the strongest algorithms in practice.

Hashing Functions Hashing functions are commonly used encryption methods. A hashing function or hash function is a special mathematical function that performs a one-way function, which means that once the algorithm is processed, there is no feasible way to use the ciphertext to retrieve the plaintext that was used to generate it. Also, ideally, there is no feasible way to generate

two different plaintexts that compute to the same hash value. The hash value is the output of the hashing algorithm for a specific input. The illustration shows the one-way nature of these functions.

Common uses of hashing algorithms are to store computer passwords and to ensure message integrity. The idea is that hashing can produce a unique value that corresponds to the data entered, but the hash value is also reproducible by anyone else running the same algorithm against the same data. So you could hash a message to get a message authentication code (MAC), and the computational number of the message would show that no intermediary has modified the message. This process works because hashing algorithms are typically public, and anyone can hash data using the specified algorithm. It is computationally simple to generate the hash, so it is simple to check the validity or integrity of something by matching the given hash to one that is locally generated. Several programs can compute hash values for an input file, as shown in Figure 5.5. Hash-based Message Authentication Code (HMAC) is a special subset of hashing technology. It is a hash algorithm applied to a message to make a MAC, but it is done with a previously shared secret. So the HMAC can provide integrity simultaneously with authentication. HMAC-MD5 is used in the NT LAN Manager version 2 challenge/response protocol.

• Figure 5.5 There are several programs available that will accept an

input and produce a hash value, letting you independently verify the integrity of downloaded content.

A hash algorithm can be compromised with what is called a collision attack, in which an attacker finds two different messages that hash to the same value. This type of attack is very difficult and requires generating a separate algorithm that attempts to find a text that will hash to the same value of a known hash. This must occur faster than simply editing characters until you hash to the same value, which is a brute-force type attack. The consequence of a hash function that suffers from collisions is a loss of integrity. If an attacker can make two different inputs purposefully hash to the same value, she might trick people into running malicious code and cause other problems. Popular hash algorithms are the Secure Hash Algorithm (SHA) series, the RIPEMD algorithms, and the Message Digest (MD) hash of varying versions (MD2, MD4, MD5). Because of weaknesses, and collision attack vulnerabilities, many hash functions are now considered to be insecure, including MD2, MD4, MD5, and SHA-1 series.

Tech Tip

Hashing Algorithms The hashing algorithms in common use are MD2, MD4, and MD5, and SHA-1, SHA-256, SHA-384, and SHA-512. Because of potential collisions, MD2, MD4, MD5, and SHA-1 have been deprecated by many groups. Although not considered secure, they are still found in use, a testament to slow adoption of better security.

Hashing functions are very common and play an important role in the way information, such as passwords, is stored securely, and the way in which messages can be signed. By computing a digest of the message, less data needs to be signed by the more complex asymmetric encryption, and this still maintains assurances about message integrity. This is the primary purpose for which the protocols were designed, and their success will

allow greater trust in electronic protocols and digital signatures.

SHA Secure Hash Algorithm (SHA) refers to a set of hash algorithms designed and published by the National Institute of Standards and Technology (NIST) and the National Security Agency (NSA). These algorithms are included in the SHA standard Federal Information Processing Standards (FIPS) 180-2 and 180-3. The individual standards are named SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512. The latter three variants are occasionally referred to collectively as SHA-2. The newest version is known as SHA-3, which is specified in FIPS 202.

SHA-1 SHA-1, developed in 1993, was designed as the algorithm to be used for secure hashing in the U.S. Digital Signature Standard (DSS). It is modeled on the MD4 algorithm and implements fixes in that algorithm discovered by the NSA. It creates message digests 160 bits long that can be used by the Digital Signature Algorithm (DSA), which can then compute the signature of the message. This is computationally simpler, as the message digest is typically much smaller than the actual message—smaller message, less work.

Tech Tip

Block Mode in Hashing Most hash algorithms use block mode to process; that is, they process all input in set blocks of data such as 512-bit blocks. The final hash is typically generated by adding the output blocks together to form the final output string of 160 or 512 bits.

SHA-1 works, as do all hashing functions, by applying a compression function to the data input. It accepts an input of up to 264 bits or less and

then compresses down to a hash of 160 bits. SHA-1 works in block mode, separating the data into words first, and then grouping the words into blocks. The words are 32-bit strings converted to hex; grouped together as 16 words, they make up a 512-bit block. If the data that is input to SHA-1 is not a multiple of 512, the message is padded with zeros and an integer describing the original length of the message. Once the message has been formatted for processing, the actual hash can be generated. The 512-bit blocks are taken in order until the entire message has been processed.

Try to keep attacks on crypto-systems in perspective. While the theory of attacking hashing through collisions is solid, finding a collision still takes enormous amounts of effort. In the case of attacking SHA-1, the collision is able to be found faster than a pure brute-force method, but by most estimates will still take several years.

At one time, SHA-1 was one of the more secure hash functions, but it has been found to be vulnerable to a collision attack. This attack found a collision in 269 computations, less than the brute-force method of 280 computations. While this is not a tremendously practical attack, it does suggest a weakness. Thus, many security professionals are suggesting that implementations of SHA-1 be moved to one of the other SHA versions. These longer versions, SHA-256, SHA-384, and SHA-512, all have longer hash results, making them more difficult to attack successfully. The added security and resistance to attack in SHA-2 does require more processing power to compute the hash.

SHA-2 SHA-2 is a collective name for SHA-224, SHA-256, SHA-384, and SHA- 512. SHA-256 is similar to SHA-1 in that it also accepts input of less than 264 bits and reduces that input to a hash. This algorithm reduces to 256 bits instead of SHA-1’s 160. Defined in FIPS 180-2 in 2002, SHA-256 is listed as an update to the original FIPS 180 that defined SHA. Similar to SHA-1,

SHA-256 uses 32-bit words and 512-bit blocks. Padding is added until the entire message is a multiple of 512. SHA-256 uses sixty-four 32-bit words, eight working variables, and results in a hash value of eight 32-bit words, hence 256 bits. SHA-224 is a truncated version of the SHA-256 algorithm that results in a 224-bit hash value. There are no known collision attacks against SHA-256; however, an attack on reduced-round SHA-256 is possible. SHA-512 is also similar to SHA-1, but it handles larger sets of data.

SHA-512 accepts 2128 bits of input, which it pads until it has several blocks of data in 1024-bit blocks. SHA-512 also uses 64-bit words instead of SHA-1’s 32-bit words. It uses eight 64-bit words to produce the 512-bit hash value. SHA-384 is a truncated version of SHA-512 that uses six 64- bit words to produce a 384-bit hash. While SHA-2 is not as common as SHA-1, more applications are

starting to utilize it after SHA-1 was shown to be potentially vulnerable to a collision attack.

SHA-3 SHA-3 is the name for the SHA-2 replacement. In 2012, the Keccak hash function won the NIST competition and was chosen as the basis for the SHA-3 method. Because the algorithm is completely different from the previous SHA series, it has proved to be more resistant to attacks that are successful against them. As the SHA-3 series is relatively new, it has not been widely adopted in many cipher suites yet.

The SHA-2 and SHA-3 series are currently approved for use. SHA-1 has been deprecated and its use discontinued in many strong cipher suites.

RIPEMD

RACE Integrity Primitives Evaluation Message Digest (RIPEMD) is a hashing function developed by the RACE Integrity Primitives Evaluation (RIPE) consortium. It originally provided a 128-bit hash and was later shown to have problems with collisions. RIPEMD was strengthened to a 160-bit hash known as RIPEMD-160 by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel. There are also 256-and 320-bit versions of the algorithm known as RIPEMD-256 and RIPEMD-320.

RIPEMD-160 RIPEMD-160 is an algorithm based on MD4, but it uses two parallel channels with five rounds. The output consists of five 32-bit words to make a 160-bit hash. There are also larger output extensions of the RIPEMD-160 algorithm. These extensions, RIPEMD-256 and RIPEMD- 320, offer outputs of 256 bits and 320 bits, respectively. While these offer larger output sizes, this does not make the hash function inherently stronger.

Message Digest Message Digest (MD) is the generic version of one of several algorithms that are designed to create a message digest or hash from data input into the algorithm. MD algorithms work in the same manner as SHA in that they use a secure method to compress the file and generate a computed output of a specified number of bits. The MD algorithms were all developed by Ronald L. Rivest of MIT.

MD2 MD2 was developed in 1989 and is in some ways an early version of the later MD5 algorithm. It takes a data input of any length and produces a hash output of 128 bits. It is different from MD4 and MD5 in that MD2 is optimized for 8-bit machines, whereas the other two are optimized for 32- bit machines. After the function has been run for every 16 bytes of the

message, the output result is a 128-bit digest. The only known attack that is successful against MD2 requires that the checksum not be appended to the message before the hash function is run. Without a checksum, the algorithm can be vulnerable to a collision attack. Some collision attacks are based upon the algorithm’s initialization vector (IV).

MD4 MD4 was developed in 1990 and is optimized for 32-bit computers. It is a fast algorithm, but it is subject to more attacks than more secure algorithms such as MD5. An extended version of MD4 computes the message in parallel and produces two 128-bit outputs—effectively a 256- bit hash. Even though a longer hash is produced, security has not been improved because of basic flaws in the algorithm. A cryptographer, Hans Dobbertin, has shown how collisions in MD4 can be found in under a minute using just a PC. This vulnerability to collisions applies to 128-bit MD4 as well as 256-bit MD4. Because of weaknesses, people have moved away from MD4 to more robust hash functions.

MD5 MD5 was developed in 1991 and is structured after MD4 but with additional security to overcome the problems in MD4. Therefore, it is very similar to the MD4 algorithm, only slightly slower and more secure.

MD5 creates a 128-bit hash of a message of any length.

Recently, successful attacks on the algorithm have occurred. Cryptanalysis has displayed weaknesses in the compression function. However, this weakness does not lend itself to an attack on MD5 itself. Czech cryptographer Vlastimil Klíma published work showing that MD5 collisions can be computed in about eight hours on a standard home PC. In

November 2007, researchers published results showing the ability to have two entirely different Win32 executables with different functionality but the same MD5 hash. This discovery has obvious implications for the development of malware. The combination of these problems with MD5 has pushed people to adopt a strong SHA version for security reasons.

Tech Tip

Rainbow Tables Rainbow tables are precomputed hash tables that enable looking up small text entries via their hash values. This makes hashed passwords “reversible” by looking up the hash in a precomputed hash table. This works for small passwords (less than 10 characters) and is very fast. Salting passwords is one of the defenses against these tables.

Hashing Summary Hashing functions are very common, and they play an important role in the way information, such as passwords, is stored securely and the way in which messages can be signed. By computing a digest of the message, less data needs to be signed by the more complex asymmetric encryption, and this still maintains assurances about message integrity. This is the primary purpose for which the protocols were designed, and their success will allow greater trust in electronic protocols and digital signatures. The following illustration shows an MD5 hash calculation in Linux.

Symmetric Encryption Symmetric encryption is the older and simpler method of encrypting information. The basis of symmetric encryption is that both the sender and the receiver of the message have previously obtained the same key. This is, in fact, the basis for even the oldest ciphers—the Spartans needed the exact same size cylinder, making the cylinder the “key” to the message, and in shift ciphers both parties need to know the direction and amount of shift being performed. All symmetric algorithms are based upon this shared secret principle, including the unbreakable one-time pad method. Figure 5.6 is a simple diagram showing the process that a symmetric

algorithm goes through to provide encryption from plaintext to ciphertext. This ciphertext message is, presumably, transmitted to the message recipient, who goes through the process to decrypt the message using the same key that was used to encrypt the message. Figure 5.6 shows the keys to the algorithm, which are the same value in the case of symmetric encryption.

• Figure 5.6 Layout of a symmetric algorithm

Unlike with hash functions, a cryptographic key is involved in symmetric encryption, so there must be a mechanism for key management (discussed earlier in the chapter). Managing the cryptographic keys is critically important in symmetric algorithms because the key unlocks the data that is being protected. However, the key also needs to be known by, or transmitted to in a confidential way, the party to which you wish to communicate. A key must be managed at all stages, which requires securing it on the local computer, securing it on the remote one, protecting it from data corruption, protecting it from loss, and, probably the most important step, protecting it while it is transmitted between the two parties. Later in the chapter we will look at public key cryptography, which greatly eases the key management issue, but for symmetric algorithms the most important lesson is to store and send the key only by known secure means. Some of the more popular symmetric encryption algorithms in use today

are DES, 3DES, AES, and IDEA.

DES DES, the Data Encryption Standard, was developed in response to the National Bureau of Standards (NBS), now known as the National Institute of Standards and Technology (NIST), issuing a request for proposals for a standard cryptographic algorithm in 1973. NBS received a promising

response in an algorithm called Lucifer, originally developed by IBM. The NBS and the NSA worked together to analyze the algorithm’s security, and eventually DES was adopted as a federal standard in 1976. DES is what is known as a block cipher; it segments the input data into

blocks of a specified size, typically padding the last block to make it a multiple of the block size required. This is in contrast to a stream cipher, which encrypts the data bit by bit. In the case of DES, the block size is 64 bits, which means DES takes a 64-bit input and outputs 64 bits of ciphertext. This process is repeated for all 64-bit blocks in the message. DES uses a key length of 56 bits, and all security rests within the key. The same algorithm and key are used for both encryption and decryption. At the most basic level, DES performs a substitution and then a

permutation (a form of transposition) on the input, based upon the key. This action is called a round, and DES performs this 16 times on every 64- bit block. The algorithm goes step by step, producing 64-bit blocks of ciphertext for each plaintext block. This is carried on until the entire message has been encrypted with DES. As mentioned, the same algorithm and key are used to decrypt and encrypt with DES. The only difference is that the sequence of key permutations is used in reverse order. Over the years that DES has been a cryptographic standard, a lot of

cryptanalysis has occurred, and while the algorithm has held up very well, some problems have been encountered. Weak keys are keys that are less secure than the majority of keys allowed in the keyspace of the algorithm. In the case of DES, because of the way the initial key is modified to get the subkey, certain keys are weak keys. The weak keys equate in binary to having all 1’s or all 0’s, like those shown in Figure 5.7, or to having half the key all 1’s and the other half all 0’s.

• Figure 5.7 Weak DES keys

Semiweak keys, with which two keys will encrypt plaintext to identical ciphertext, also exist, meaning that either key will decrypt the ciphertext. The total number of possibly weak keys is 64, which is very small relative to the 256 possible keys in DES. With 16 rounds and not using a weak key, DES is reasonably secure

and, amazingly, has been for more than two decades. In 1999, a distributed effort consisting of a supercomputer and 100,000 PCs over the Internet was made to break a 56-bit DES key. By attempting more than 240 billion keys per second, the effort was able to retrieve the key in less than a day. This demonstrates an incredible resistance to cracking a 20-year-old algorithm, but it also demonstrates that more stringent algorithms are needed to protect data today.

3DES Triple DES (3DES) is a variant of DES. Depending on the specific variant, it uses either two or three keys instead of the single key that DES uses. It also spins through the DES algorithm three times via what’s called multiple encryption. Multiple encryption can be performed in several different ways. The

simplest method of multiple encryption is just to stack algorithms on top of each other—taking plaintext, encrypting it with DES, then encrypting the first ciphertext with a different key, and then encrypting the second ciphertext with a third key. In reality, this technique is less effective than the technique that 3DES uses. One of the modes of 3DES (EDE mode) is to encrypt with one key, then decrypt with a second, and then encrypt with a third, as shown in Figure 5.8.

• Figure 5.8 Diagram of 3DES

This greatly increases the number of attempts needed to retrieve the key and is a significant enhancement of security. The additional security comes at a price, however. It can take up to three times longer to compute 3DES than to compute DES. However, the advances in memory and processing

power in today’s electronics should make this problem irrelevant in all devices except for very small low-power handhelds. The only weaknesses of 3DES are those that already exist in DES.

However, due to the use of different keys in the same algorithm, effecting a longer key length by adding the first keyspace to the second keyspace, and the greater resistance to brute-forcing, 3DES has less actual weakness. While 3DES continues to be popular and is still widely supported, AES has taken over as the symmetric encryption standard.

AES The current gold standard for symmetric encryption is the AES algorithm. Developed in response to a worldwide call in the late 1990s for a new symmetric cipher, a group of Dutch researchers submitted a method called Rijndael (pronounced “rain doll”). In the fall of 2000, NIST picked Rijndael to be the new AES. It was

chosen for its overall security as well as its good performance on limited- capacity devices. Rijndael’s design was influenced by Square, also written by Joan Daemen and Vincent Rijmen. Like Square, Rijndael is a block cipher that separates data input into 128-bit blocks. Rijndael can also be configured to use blocks of 192 or 256 bits, but AES has standardized on 128-bit blocks. AES can have key sizes of 128, 192, and 256 bits, with the size of the key affecting the number of rounds used in the algorithm. Longer key versions are known as AES-192 and AES-256, respectively.

Tech Tip

AES in Depth For a more in-depth description of AES, see the NIST document http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf.

The Rijndael/AES algorithm is well thought out and has a suitable key

length to provide security for many years to come. While no efficient attacks currently exist against AES, more time and analysis will tell if this standard can last as long as DES has.

CAST CAST is an encryption algorithm that is similar to DES in its structure. It was designed by Carlisle Adams and Stafford Tavares. CAST uses a 64-bit block size for 64- and 128-bit key versions, and a 128-bit block size for the 256-bit key version. Like DES, it divides the plaintext block into a left half and a right half. The right half is then put through function f and then is XORed with the left half. This value becomes the new right half, and the original right half becomes the new left half. This is repeated for eight rounds for a 64-bit key, and the left and right output is concatenated to form the ciphertext block. The algorithm in CAST-256 form was submitted for the AES standard but was not chosen. CAST has undergone thorough analysis, with only minor weaknesses discovered that are dependent on low numbers of rounds. Currently, no better way is known to break high-round CAST than by brute-forcing the key, meaning that with sufficient key length, CAST should be placed with other trusted algorithms.

RC RC is a general term for several ciphers all designed by Ron Rivest—RC officially stands for Rivest Cipher. RC1, RC2, RC3, RC4, RC5, and RC6 are all ciphers in the series. RC1 and RC3 never made it to release, but RC2, RC4, RC5, and RC6 are all working algorithms.

RC2 RC2 was designed as a DES replacement, and it is a variable-key-size block-mode cipher. The key size can be from 8 bits to 1024 bits, with the block size being fixed at 64 bits. RC2 breaks up the input blocks into four

16-bit words and then puts them through 18 rounds of either mix or mash operations, outputting 64 bits of ciphertext for 64 bits of plaintext. According to RSA, RC2 is up to three times faster than DES. RSA

maintained RC2 as a trade secret for a long time, with the source code eventually being illegally posted on the Internet. The ability of RC2 to accept different key lengths is one of the larger vulnerabilities in the algorithm. Any key length below 64 bits can be easily retrieved by modern computational power. Additionally, there is a related key attack that needs 234 chosen plaintexts to work. Considering these weaknesses, RC2 is not recommended as a strong cipher.

RC5 RC5 is a block cipher, written in 1994. It has multiple variable elements, numbers of rounds, key sizes, and block sizes. This algorithm is relatively new, but if configured to run enough rounds, RC5 seems to provide adequate security for current brute-forcing technology. Rivest recommends using at least 12 rounds. With 12 rounds in the algorithm, cryptanalysis in a linear fashion proves less effective than brute-force against RC5, and differential analysis fails for 15 or more rounds. A newer algorithm is RC6.

RC6 RC6 is based on the design of RC5. It uses a 128-bit block size, separated into four words of 32 bits each. It uses a round count of 20 to provide security, and it has three possible key sizes: 128, 192, and 256 bits. RC6 is a modern algorithm that runs well on 32-bit computers. With a sufficient number of rounds, the algorithm makes both linear and differential cryptanalysis infeasible. The available key lengths make brute-force attacks extremely time-consuming. RC6 should provide adequate security for some time to come.

RC4

RC4 was created before RC5 and RC6, but it differs in operation. RC4 is a stream cipher, whereas all the symmetric ciphers we have looked at so far have been block ciphers. A stream cipher works by enciphering the plaintext in a stream, usually bit by bit. This makes stream ciphers faster than block-mode ciphers. Stream ciphers accomplish this by performing a bitwise XOR with the plaintext stream and a generated keystream. RC4 operates in this manner. It was developed in 1987 and remained a

trade secret of RSA until it was posted to the Internet in 1994. RC4 can use a key length of 8 to 2048 bits, though the most common versions use 128- bit keys or, if subject to the old export restrictions, 40-bit keys. The key is used to initialize a 256-byte state table. This table is used to generate the pseudo-random stream that is XORed with the plaintext to generate the ciphertext. Alternatively, the stream is XORed with the ciphertext to produce the plaintext. The algorithm is fast, sometimes ten times faster than DES. The most

vulnerable point of the encryption is the possibility of weak keys. One key in 256 can generate bytes closely correlated with key bytes. Proper implementations of RC4 need to include weak key detection.

RC4 is the most widely used stream cipher and is used in popular protocols such as Transport Layer Security (TLS) and WEP/WPA/WPA2.

Blowfish Blowfish was designed in 1994 by Bruce Schneier. It is a block-mode cipher using 64-bit blocks and a variable key length from 32 to 448 bits. It was designed to run quickly on 32-bit microprocessors and is optimized for situations with few key changes. Encryption is done by separating the 64-bit input block into two 32-bit words, and then a function is executed every round. Blowfish has 16 rounds; once the rounds are completed, the

two words are then recombined to form the 64-bit output ciphertext. The only successful cryptanalysis to date against Blowfish has been against variants that used a reduced number of rounds. There does not seem to be a weakness in the full 16-round version.

Twofish Twofish was developed by Bruce Schneier, David Wagner, Chris Hall, Niels Ferguson, John Kelsey, and Doug Whiting. Twofish was one of the five finalists for the AES competition. Like other AES entrants, it is a block cipher, utilizing 128-bit blocks with a variable-length key of up to 256 bits. It uses 16 rounds and splits the key material into two sets, one to perform the actual encryption and the other to load into the algorithm’s S- boxes. This algorithm is available for public use and has proven to be secure.

Tech Tip

S-Boxes S-boxes, or substitution boxes, are a method used to provide confusion, a separation of the relationship between the key bits and the ciphertext bits. Used in most symmetric schemes, they perform a form of substitution and can provide significant strengthening of an algorithm against certain forms of attack. They can be in the form of lookup tables, either static like DES, or dynamic (based on the key) in other forms such as Twofish.

IDEA IDEA (International Data Encryption Algorithm) started out as PES, or Proposed Encryption Cipher, in 1990, and it was modified to improve its resistance to differential cryptanalysis and its name was changed to IDEA in 1992. It is a block-mode cipher using a 64-bit block size and a 128-bit key. The input plaintext is split into four 16-bit segments, A, B, C, and D.

The process uses eight rounds, with a final four-step process. The output of the last four steps is then concatenated to form the ciphertext. All current cryptanalysis on full, eight-round IDEA shows that the most

efficient attack would be to brute-force the key. The 128-bit key would prevent this attack being accomplished, given current computer technology. The only known issue is that IDEA is susceptible to a weak key—like a key that is made of all 0’s. This weak key condition is easy to check for, and the weakness is simple to mitigate.

Block vs. Stream When encryption operations are performed on data, there are two primary modes of operation, block and stream. Block operations are performed on blocks of data, enabling both transposition and substitution operations. This is possible when large pieces of data are present for the operations. Stream data has become more common with audio and video across the Web. The primary characteristic of stream data is that it is not available in large chunks, but either bit by bit or byte by byte, pieces too small for block operations. Stream ciphers operate using substitution only and therefore offer less robust protection than block ciphers. Table 5.1 compares and contrasts block and stream ciphers.

Table 5.1 Comparison of Block and Stream Ciphers

Symmetric Encryption Summary Symmetric algorithms are important because they are comparatively fast and have few computational requirements. Their main weakness is that two geographically distant parties both need to have a key that matches the other key exactly (see Figure 5.9).

• Figure 5.9 Symmetric keys must match exactly to encrypt and decrypt the message.

Asymmetric Encryption Asymmetric encryption is more commonly known as public key cryptography. Asymmetric encryption is in many ways completely different from symmetric encryption. While both are used to keep data from being seen by unauthorized users, asymmetric cryptography uses two keys instead of one. It was invented by Whitfield Diffie and Martin Hellman in 1975. The system uses a pair of keys: a private key that is kept secret and a public key that can be sent to anyone. The system’s security relies upon resistance to deducing one key, given the other, and thus retrieving the plaintext from the ciphertext. Asymmetric encryption creates the possibility of digital signatures and

also addresses the main weakness of symmetric cryptography. The ability to send messages securely without senders and receivers having had prior contact has become one of the basic concerns with secure communication. Digital signatures will enable faster and more efficient exchange of all kinds of documents, including legal documents. With strong algorithms and good key lengths, security can be assured. Asymmetric encryption involves two separate but mathematically

related keys. The keys are used in an opposing fashion. One key undoes the actions of the other and vice versa. So, as shown in Figure 5.10, if you encrypt a message with one key, the other key is used to decrypt the message. In the top example, Alice wishes to send a private message to Bob, so she uses Bob’s public key to encrypt the message. Then, since only Bob’s private key can decrypt the message, only Bob can read it. In the lower example, Bob wishes to send a message, with proof that it is from him. By encrypting it with his private key, anyone who decrypts it with his public key knows the message came from Bob.

• Figure 5.10 Using an asymmetric algorithm

Public key cryptography always involves two keys, a public key and a private key, which together are known as a key pair. The public key is made widely available to anyone who may need it, while the private key is closely safeguarded and shared with no one.

Asymmetric keys are distributed using certificates. A digital certificate contains information about the association of the public key to an entity, and additional information that can be used to verify the current validity of the certificate and the key. When keys are exchanged between machines, such as during an SSL/TLS handshake, the exchange is done by passing certificates.

Asymmetric methods are significantly slower than symmetric methods and thus are typically not suitable for bulk encryption.

Public key systems typically work by using hard math problems. One of the more common methods relies on the difficulty of factoring large numbers. These functions are often called trapdoor functions, as they are difficult to process without the key but easy to process when you have the key—the trapdoor through the function. For example, given a prime number, say 293, and another prime, such as 307, it is an easy function to multiply them together to get 89,951. Given 89,951, it is not simple to find the factors 293 and 307 unless you know one of them already. Computers can easily multiply very large primes with hundreds or thousands of digits but cannot easily factor the product. The strength of these functions is very important: Because an attacker is

likely to have access to the public key, he can run tests of known plaintext and produce ciphertext. This allows instant checking of guesses that are made about the keys of the algorithm. Public key systems, because of their design, also form the basis for digital signatures, a cryptographic method for securely identifying people. RSA, Diffie-Hellman, elliptic curve cryptography (ECC), and ElGamal are all popular asymmetric protocols. We will look at all of them and their suitability for different functions.

Cross Check Digital Certificates In Chapter 6 you will learn more about digital certificates and how encryption is important to a public key infrastructure. Why is an asymmetric algorithm so important to digital signatures?

Diffie-Hellman

Diffie-Hellman (DH) was created in 1976 by Whitfield Diffie and Martin Hellman. This protocol is one of the most common encryption protocols in use today. It plays a role in the electronic key exchange method of the Secure Sockets Layer (SSL) protocol. It is also used by the Transport Layer Security (TLS), Secure Shell (SSH), and IP Security (IPsec) protocols. Diffie-Hellman is important because it enables the sharing of a secret key between two people who have not contacted each other before. The protocol, like RSA, uses large prime numbers to work. Two users

agree to two numbers, P and G, with P being a sufficiently large prime number and G being the generator. Both users pick a secret number, a and b. Then both users compute their public number:

User 1 X = Ga mod P, with X being the public number User 2 Y = Gb mod P, with Y being the public number

The users then exchange public numbers. User 1 knows P, G, a, X, and Y.

User 1 Computes Ka = Ya mod P User 2 Computes Kb = Xb mod P

With Ka = Kb = K, now both users know the new shared secret K. This is the basic algorithm, and although methods have been created to

strengthen it, Diffie-Hellman is still in wide use. It remains very effective because of the nature of what it is protecting—a temporary, automatically generated secret key that is good only for a single communication session. Variations of Diffie-Hellman include Ephemeral Diffie-Hellman (EDH),

Elliptic Curve Diffie-Hellman (ECDH), and Elliptic Curve Diffie-Hellman Ephemeral (ECDHE). These are discussed in detail later in the chapter.

Diffie-Hellman is the gold standard for key exchange, and for the CompTIA Security+ exam, you should understand the subtle differences between the different forms, DH, EDH, ECDH, and ECDHE.

RSA RSA is one of the first public key cryptosystems ever invented. It can be used for both encryption and digital signatures. RSA is named after its inventors, Ron Rivest, Adi Shamir, and Leonard Adleman, and was first published in 1977. This algorithm uses the product of two very large prime numbers and

works on the principle of difficulty in factoring such large numbers. It’s best to choose large prime numbers that are from 100 to 200 digits in length and are equal in length. These two primes will be P and Q. Randomly choose an encryption key, E, so that E is greater than 1, E is less than P * Q, and E must be odd. E must also be relatively prime to (P – 1) and (Q – 1). Then compute the decryption key D:

D = E–1 mod ((P – 1)(Q – 1)) Now that the encryption key and decryption key have been generated,

the two prime numbers can be discarded, but they should not be revealed. To encrypt a message, it should be divided into blocks less than the

product of P and Q. Then,

Ci = Mi E mod (P * Q)

C is the output block of ciphertext matching the block length of the input message, M. To decrypt a message, take ciphertext, C, and use this function:

Mi = Ci D mod (P * Q)

The use of the second key retrieves the plaintext of the message. This is a simple function, but its security has withstood the test of more

than 20 years of analysis. Considering the effectiveness of RSA’s security and the ability to have two keys, why are symmetric encryption algorithms needed at all? The answer is speed. RSA in software can be 100 times slower than DES, and in hardware it can be even slower. RSA can be used to perform both regular encryption and digital

signatures. Digital signatures try to duplicate the functionality of a physical signature on a document using encryption. Typically, RSA and the other public key systems are used in conjunction with symmetric key cryptography. Public key, the slower protocol, is used to exchange the symmetric key (or shared secret), and then the communication uses the faster symmetric key protocol. This process is known as electronic key exchange. Since the security of RSA is based upon the supposed difficulty of

factoring large numbers, the main weaknesses are in the implementations of the protocol. Until recently, RSA was a patented algorithm, but it was a de facto standard for many years.

ElGamal ElGamal can be used for both encryption and digital signatures. Taher ElGamal designed the system in the early 1980s. This system was never patented and is free for use. It is used as the U.S. government standard for digital signatures. The system is based upon the difficulty of calculating discrete

logarithms in a finite field. Three numbers are needed to generate a key pair. User 1 chooses a prime, P, and two random numbers, F and D. F and D should both be less than P. Then user 1 can calculate the public key A:

A = DF mod P Then A, D, and P are shared with the second user, with F being the private key. To encrypt a message, M, a random key, k, is chosen that is relatively prime to P – 1. Then,

C1 = D k mod P

C2 = A kM mod P

C1 and C2 make up the ciphertext. Decryption is done by

M = C2/C1 F mod P

ElGamal uses a different function for digital signatures. To sign a message, M, once again choose a random value k that is relatively prime to P –1. Then,

C1 = D k mod P

C2 = (M – C1 * F)/k (mod P – 1)

C1 concatenated to C2 is the digital signature. ElGamal is an effective algorithm and has been in use for some time. It

is used primarily for digital signatures. Like all asymmetric cryptography, it is slower than symmetric cryptography.

ECC Elliptic curve cryptography (ECC) works on the basis of elliptic curves. An elliptic curve is a simple function that is drawn as a gently looping curve on the X,Y plane. Elliptic curves are defined by this equation:

y2 = x3 + ax2 + b Elliptic curves work because they have a special property—you can add two points on the curve together and get a third point on the curve, as shown in the illustration.

For cryptography, the elliptic curve works as a public key algorithm. Users agree on an elliptic curve and a fixed curve point. This information is not a shared secret, and these points can be made public without compromising the security of the system. User 1 then chooses a secret random number, K1, and computes a public key based upon a point on the curve:

P1 = K1 * F

User 2 performs the same function and generates P2. Now user 1 can send user 2 a message by generating a shared secret:

S = K1 * P2 User 2 can generate the same shared secret independently:

S = K2 * P1 This is true because

K1 * P2 = K1 * (K2 * F) = (K1 * K2) * F = K2 * (K1 * F) = K2 * P1 The security of elliptic curve systems has been questioned, mostly

because of lack of analysis. However, all public key systems rely on the difficulty of certain math problems. It would take a breakthrough in math for any of the mentioned systems to be weakened dramatically, but research has been done about the problems and has shown that the elliptic curve problem has been more resistant to incremental advances. Again, as with all cryptography algorithms, only time will tell how secure they really are. The big benefit to ECC systems is that they require less computing power for a given bit strength. This makes ECC ideal for use in low-power mobile devices. The surge in mobile connectivity has led to secure voice, e-mail, and text applications that use ECC and AES algorithms to protect a user’s data. Elliptic curve functions can be used as part of a Diffie-Hellman key

exchange, and when used, the method is referred to as Elliptic Curve DIffie-Hellman (ECDH). This technique can provide the advantages of elliptic curve and the functionality of Diffie-Hellman.

Asymmetric Encryption Summary Asymmetric encryption creates the possibility of digital signatures and also corrects the main weakness of symmetric cryptography. The ability to send messages securely without senders and receivers having had prior contact has become one of the basic concerns with secure communication. Digital signatures will enable faster and more efficient exchange of all kinds of documents, including legal documents. With strong algorithms

and good key lengths, security can be assured.

Symmetric vs. Asymmetric Both symmetric and asymmetric encryption methods have advantages and disadvantages. Symmetric encryption tends to be faster, is less computationally involved, and is better for bulk transfers. But it suffers from a key management problem in that keys must be protected from unauthorized parties. Asymmetric methods resolve the key secrecy issue with public keys, but add significant computational complexity that makes them less suited for bulk encryption. Bulk encryption can be done using the best of both systems, by using

asymmetric encryption to pass a symmetric key. By adding in ephemeral key exchange, you can achieve perfect forward secrecy, discussed later in the chapter. Digital signatures, a highly useful tool, are not practical without asymmetric methods.

Quantum Cryptography Cryptography is traditionally a very conservative branch of information technology. It relies on proven technologies and does its best to resist change. A big new topic in recent years has been quantum cryptography. Quantum cryptography is based on quantum mechanics, principally superposition and entanglement. A discussion of quantum mechanics is beyond the scope of this text, but the principle we are most concerned with in regard to cryptography is that in quantum mechanics, the measuring of data disturbs the data. What this means to cryptographers is that it is easy to tell if a message has been eavesdropped on in transit, allowing people to exchange key data while knowing that the data was not intercepted in transit. This use of quantum cryptography is called quantum key distribution. This is currently the only commercial use of quantum cryptography, and although there are several methods for sending the key, they all adhere to the same principle. Key bits are sent and then checked at

the remote end for interception, and then more key bits are sent using the same process. Once an entire key has been sent securely, symmetric encryption can then be used. The other field of research involving quantum mechanics and

cryptography is quantum cryptanalysis. A quantum computer is capable of factoring large primes exponentially faster than a normal computer, potentially making the RSA algorithm, and any system based upon factoring prime numbers, insecure. This has led to research in cryptosystems that are not vulnerable to quantum computations, a field known as post-quantum cryptography.

Steganography Steganography, an offshoot of cryptography technology, gets its meaning from the Greek word steganos, meaning covered. Invisible ink placed on a document hidden by innocuous text is an example of a steganographic message. Another example is a tattoo placed on the top of a person’s head, visible only when the person’s hair is shaved off. Hidden writing in the computer age relies on a program to hide data

inside other data. The most common application is the concealing of a text message in a picture file. The Internet contains multiple billions of image files, allowing a hidden message to be located almost anywhere without being discovered. Because not all detection programs can detect every kind of steganography, trying to find the message in an Internet image is akin to attempting to find a needle in a haystack the size of the Pacific Ocean; even a Google search for steganography returns thousands of images.

The nature of the image files also makes a hidden message difficult to detect. While it is most common to hide messages inside images, they can also be hidden in video and audio files. The advantage to steganography over the use of encryption alone is that

the messages do not attract attention, and this difficulty in detecting the

hidden message provides an additional barrier to analysis. The data that is hidden in a steganographic message is frequently also encrypted, so that if it is discovered, the message will remain secure. Steganography has many uses but the most publicized uses are to hide illegal material, often pornography, or allegedly for covert communication by terrorist networks. Steganographic encoding can be used in many ways and through many

different media. Covering them all is beyond the scope for this book, but we will discuss one of the most common ways to encode into an image file, LSB encoding. LSB, Least Significant Bit, is a method of encoding information into an image while altering the actual visual image as little as possible. A computer image is made up of thousands or millions of pixels, all defined by 1’s and 0’s. If an image is composed of Red Green Blue (RGB) values, each pixel has an RGB value represented numerically from 0 to 255. For example, 0,0,0 is black, and 255,255,255 is white, which can also be represented as 00000000, 00000000, 00000000 for black and 11111111, 11111111, 11111111 for white. Given a white pixel, editing the least significant bit of the pixel to 11111110, 11111110, 11111110 changes the color. The change in color is undetectable to the human eye, but in an image with a million pixels, this creates a 125KB area in which to store a message. Some popular steganography detection tools include Stegdetect,

StegSecret, StegSpy, and the family of SARC tools. All of these tools use detection techniques based upon the same principle, pattern detection. By looking for known steganographic encoding schemes or artifacts, they can potentially detect embedded data. Additionally, steganography insertion tools can be used to attempt to decode images with suspected hidden messages. Invisible Ink is a small program for steganographic insertion of messages and then the extraction of those messages, as illustrated here.

Cryptography Algorithm Use

The use of cryptographic algorithms grows every day. More and more information becomes digitally encoded and placed online, and all of this data needs to be secured. The best way to do that with current technology is to use encryption. This section considers some of the tasks cryptographic algorithms accomplish and those for which they are best suited. Security is typically defined as a product of five components: confidentiality, integrity, availability, authentication, and nonrepudiation. Encryption addresses all of these components except availability. Key escrow will be one of the most important topics as information becomes universally encrypted; otherwise, everyone may be left with useless data. Digital rights management and intellectual property protection are also places where encryption algorithms are heavily used. Digital signatures combine several algorithms to provide reliable identification in a digital form.

Confidentiality Confidentiality typically comes to mind when the term security is brought up. Confidentiality is the ability to keep some piece of data a secret. In the digital world, encryption excels at providing confidentiality. In most cases, symmetric encryption is favored because of its speed and because some asymmetric algorithms can significantly increase the size of the object being encrypted. Asymmetric cryptography also can be used to protect confidentiality, but its size and speed make it more efficient at protecting the confidentiality of small units for tasks such as electronic key exchange. In all cases, the strength of the algorithms and the length of the keys ensure the secrecy of the data in question.

Integrity Integrity, better known as message integrity, is a crucial component of message security. When a message is sent, both the sender and recipient need to know that the message was not altered in transmission. This is

especially important for legal contracts—recipients need to know that the contracts have not been altered. Signers also need a way to validate that a contract they sign will not be altered in the future.

Message integrity will become increasingly important as more commerce is conducted digitally. The ability to independently make sure that a document has not been tampered with is very important to commerce. More importantly, once the document is “signed” with a digital signature, it cannot be refuted that the person in question signed it.

Integrity is provided via one-way hash functions and digital signatures. The hash functions compute the message digests, and this guarantees the integrity of the message by allowing easy testing to determine whether any part of the message has been changed. The message now has a computed function (the hash value) to tell the users to resend the message if it was intercepted and interfered with. This hash value is combined with asymmetric cryptography by taking the message’s hash value and encrypting it with the user’s private key. This lets anyone with the user’s public key decrypt the hash and compare it to the locally computed hash, not only ensuring the integrity of the message but positively identifying the sender.

Authentication Authentication is the matching of a user to an account through previously shared credentials. This information must be protected and a combination of cryptographic methods are commonly employed. From hashing to key stretching to encryption and digital signatures, multiple techniques are used as part of the operations involved in authentication.

Try This!

Document Integrity Download a hash calculator that works on your operating system, such as SlavaSoft HashCalc, available at www.slavasoft.com/hashcalc/index.htm. Then create a simple document file with any text that you prefer. Save it, and then use the hashing program to generate the hash and save the hash value. Now edit the file, even by simply inserting a single blank space, and resave it. Recalculate the hash and compare.

Nonrepudiation An item of some confusion, the concept of nonrepudiation is actually fairly simple. Nonrepudiation means that the message sender cannot later deny that they sent the message. This is important in electronic exchanges of data, because of the lack of face-to-face meetings. Nonrepudiation is based upon public key cryptography and the principle of only you knowing your private key. The presence of a message signed by you, using your private key, which nobody else should know, is an example of nonrepudiation. When a third party can check your signature using your public key, that disproves any claim that you were not the one who actually sent the message. Nonrepudiation is tied to asymmetric cryptography and cannot be implemented with symmetric algorithms.

Tech Tip

HOTP An HMAC-based One-Time Password (HOTP) algorithm is a key component of the Open Authentication Initiative (OATH). YubiKey is a hardware implementation of HOTP that has significant use.

Cipher Suites In many applications, the use of cryptography occurs as a collection of functions. Different algorithms can be used for authentication,

encryption/decryption, digital signatures, and hashing. The term cipher suite refers to an arranged group of algorithms. For instance, TLS has a published TLS Cipher Suite Registry at www.iana.org/assignments/tls- parameters/tls-parameters.xhtml.

Strong vs. Weak Ciphers There is a wide range of ciphers, some old and some new, each with its own strengths and weaknesses. Over time, new methods and computational abilities change the viability of ciphers. The concept of strong versus weak ciphers is an acknowledgment that, over time, ciphers can become vulnerable to attacks. The application or selection of ciphers should take into consideration that not all ciphers are still strong. When selecting a cipher for use, it is important to make an appropriate choice.

Key Exchange Cryptographic mechanisms use both an algorithm and a key, with the key requiring communication between parties. In symmetric encryption, the secrecy depends upon the secrecy of the key, so insecure transport of the key can lead to failure to protect the information encrypted using the key. Key exchange is the central foundational element of a secure symmetric encryption system. Maintaining the secrecy of the symmetric key is the basis of secret communications. In asymmetric systems, the key exchange problem is one of key publication. Because public keys are designed to be shared, the problem is reversed from one of secrecy to one of publicity. Early key exchanges were performed by trusted couriers. People carried

the keys from senders to receivers. One could consider this form of key exchange to be the ultimate in out-of-band communication. With the advent of digital methods and some mathematical algorithms, it is possible to pass keys in a secure fashion. This can occur even when all packets are subject to interception. The Diffie-Hellman key exchange is one example of this type of secure key exchange. The Diffie-Hellman key exchange depends upon two random numbers, each chosen by one of the parties, and

kept secret. Diffie-Hellman key exchanges can be performed in-band, and even under external observation, as the secret random numbers are never exposed to outside parties.

Key Escrow The impressive growth of the use of encryption technology has led to new methods for handling keys. Encryption is adept at hiding all kinds of information, and with privacy and identity protection becoming more of a concern, more information is encrypted. The loss of a key can happen for a multitude of reasons: it might simply be lost, the key holder might be incapacitated or dead, software or hardware might fail, and so on. In many cases, that information is locked up until the cryptography can be broken, and, as you have read, that could be millennia. This has raised the topic of key escrow, or keeping a copy of the encryption key with a trusted third party. Theoretically, this third party would only release your key to you or your official designate on the event of your being unable to get the key yourself. However, just as the old saying from Benjamin Franklin goes, “Three may keep a secret if two of them are dead.” Anytime more than one copy of the key exists, the security of the system is broken. The extent of the insecurity of key escrow is a subject open to debate, and will be hotly contested in the years to come.

Tech Tip

Key Escrow Has Benefits and Hazards Key escrow can solve many of the problems that result when a key is lost or becomes inaccessible, allowing access to data that otherwise would be impossible to access without key escrow, but it can open up private information to unauthorized access.

Additionally, with computer technology being miniaturized into smartphones and other relatively inexpensive devices, criminals and other

ill-willed people have begun using cryptography to conceal communications and business dealings from law enforcement agencies. Because law enforcement agencies have not been able to break the encryption in many cases, government agencies have begun asking for mandatory key escrow legislation. In this sense, key escrow is a system by which your private key is kept both by you and by the government. This allows people with a court order to retrieve your private key to gain access to anything encrypted with your public key. The data is essentially encrypted by your key and the government key, giving the government access to your plaintext data. This process is similar to a search warrant of your home, but is used against your computer data. Whether or not this is how things should be is also open to debate, but it does raise the interesting possibility of encryption software that is incompatible with government key escrow being banned. The last major discussion for key escrow legislation was several years ago, but the prospect remains out there waiting for a high profile case to bring encryption into the spotlight. In 2015, many US Federal officials again called for forms of key escrow and back doors in the name of anti-terrorism and law enforcement. The result of this new round of argument will take years to decide the correct balance. Key escrow can negatively impact the security provided by encryption,

because the government requires a huge, complex infrastructure of systems to hold every escrowed key, and the security of those systems is less efficient than the security of your memorizing the key. However, there are two sides to the key escrow coin. Without a practical way to recover a key if or when it is lost or the key holder dies, for example, some important information will be lost forever. Such issues will affect the design and security of encryption technologies for the foreseeable future.

Session Keys A session key is a symmetric key used for encrypting messages during a communication session. It is generated from random seeds and is used for

the duration of a communication session. When correctly generated and propagated during session setup, a session key provides significant levels of protection during the communication session and also can afford perfect forward secrecy (described later in the chapter). Session keys offer the advantages of symmetric encryption, speed, strength, simplicity, and, with key exchanges possible via digital methods, significant levels of automated security.

Ephemeral Keys Ephemeral keys are cryptographic keys that are used only once after they are generated. When an ephemeral key is used as part of the Diffie- Hellman scheme, it forms an Ephemeral Diffie-Hellman (EDH) key exchange. An EDH mechanism generates a temporary key for each connection, never using the same key twice. This provides for perfect forward secrecy. If the Diffie-Hellman involves the use of elliptic curves, it is called Elliptic Curve Diffie-Hellman Ephemeral (ECDHE).

Key Stretching Key stretching is a mechanism that takes what would be weak keys and “stretches” them to make the system more secure against brute-force attacks. A typical methodology used for key stretching involves increasing the computational complexity by adding iterative rounds of computations. To extend a password to a longer length of key, you can run it through multiple rounds of variable-length hashing, each increasing the output by bits over time. This may take hundreds or thousands of rounds, but for single-use computations, the time is not significant. When one wants to use a brute-force attack, the increase in computational workload becomes significant when done billions of times, making this form of attack much more expensive. The common forms of key stretching employed in use today include

Password-Based Key Derivation Function 2 and Bcrypt.

PBKDF2 Password-Based Key Derivation Function 2 (PBKDF2) is a key derivation function designed to produce a key derived from a password. This function uses a password or passphrase and a salt and applies an HMAC to the input thousands of times. The repetition makes brute-force attacks computationally unfeasible.

Bcrypt Bcrypt is a key-stretching mechanism that uses the Blowfish cipher and salting, and adds an adaptive function to increase the number of iterations. The result is the same as other key-stretching mechanisms (single use is computationally feasible), but when attempting to brute-force the function, the billions of attempts make it computationally unfeasible.

Secrecy Principles There are several conditions and principles associated with secrecy. Two of these, confusion and diffusion, arise from Claude Shannon’s seminal work in communication theory. The concept of entropy, presented earlier, is from the same source. While these are theoretical-centric ideas, there are implementation principles as well. Perfect forward secrecy is one of these as it applies to future message secrecy.

Confusion Confusion is a principle to affect the randomness of an output. The concept is operationalized by ensuring that each character of ciphertext depends on several parts of the key. Confusion places a constraint on the relationship between the ciphertext and the key employed, forcing an effect that increases entropy.

Diffusion Diffusion is a principle that the statistical analysis of plaintext and

ciphertext results in a form of dispersion rendering one structurally independent of the other. In plain terms, a change in one character of plaintext should result in multiple changes in the ciphertext in a manner that changes in ciphertext do not reveal information as to the structure of the plaintext.

Perfect Forward Secrecy Perfect forward secrecy is a property of a public key system in which a key derived from another key is not compromised even if the originating key is compromised in the future. This is especially important in session key generation, where the compromise of future communication sessions may become compromised; if perfect forward secrecy were not in place, then past messages that had been recorded could be decrypted.

Transport Encryption Transport encryption is used to protect data that is in motion. When data is being transported across a network, it is at risk of interception. An examination of the OSI networking model shows a layer dedicated to transport, and this abstraction can be used to manage end-to-end cryptographic functions for a communication channel. When utilizing the TCP/IP protocol, TLS is the preferred method of managing the security at the transport level.

Digital Signatures Digital signatures have been touted as the key to truly paperless document flow, and they do have promise for improving the system. Digital signatures are based on both hashing functions and asymmetric cryptography. Both encryption methods play an important role in signing digital documents. Unprotected digital documents are very easy for anyone to change. If a document is edited after an individual signs it, it is important that any modification can be detected. To protect against

document editing, hashing functions are used to create a digest of the message that is unique and easily reproducible by both parties. This ensures that the message integrity is complete.

Digital signatures provide a means of verifying authenticity and integrity of a message: you know both who the sender is and that the message has not been altered. By itself, a digital signature does not protect the contents from unauthorized reading.

A digital signature is a cryptographic implementation designed to demonstrate authenticity and identity associated with a message. Using public key cryptography, a digital signature allows traceability to the person signing the message through the use of their private key. The addition of hash codes allows for the assurance of integrity of the message as well. The operation of a digital signature is a combination of cryptographic elements to achieve a desired outcome. The steps involved in digital signature generation and use are illustrated in Figure 5.11. The message to be signed is hashed, and the hash is encrypted using the sender’s private key. Upon receipt, the recipient can decrypt the hash using the sender’s public key. If a subsequent hashing of the message reveals an identical value, two things are known: First, the message has not been altered. Second, the sender possessed the private key of the named sender, so is presumably the sender him- or herself.

• Figure 5.11 Digital signature operation

A digital signature does not by itself protect the contents of the message from interception. The message is still sent in the clear, so if confidentiality of the message is a requirement, additional steps must be taken to secure the message from eavesdropping. This can be done by encrypting the message itself, or by encrypting the channel over which it is transmitted.

Digital Rights Management Digital rights management (DRM) is the process for protecting intellectual property from unauthorized use. This is a broad area, but the most concentrated focus is on preventing piracy of software or digital content. Before easy access to computers, or the “digital revolution,” the content we came in contact with was analog or print based. While it was possible to copy this content, it was difficult and time-consuming to do so, and usually resulted in a loss of quality. It was also much more difficult to send 1000 pages of a handwritten copy of a book to Europe, for example. Computers and the Internet have made such tasks trivial, and now it is very easy to copy a document, music, or video and quickly send it thousands of miles away. Cryptography has entered the fray as a solution to protect digital rights,

though it is currently better known for its failures than its successes. The DVD Content Scramble System (CSS) was an attempt to make DVDs impossible to copy by computer. CSS used an encryption algorithm that was licensed to every DVD player; however, creative programmers were able to retrieve the key to this algorithm by disassembling a software- based DVD player. CSS has been replaced by the Advanced Access Content System (AACS), which is used on the next-generation Blu-ray discs. This system encrypts video content via the symmetric AES algorithm with one or more keys. Several decryption keys have been

cracked and released to the Internet, allowing pirates to freely copy the protected content. The music and computer game industries have also attempted several different DRM applications, but nearly all of these have eventually been cracked, allowing piracy. A common example of DRM that is mostly successful is the broadcast

stream of digital satellite TV. Since the signal is beamed from space to every home in North America, the satellite TV provider must be able to protect the signal so that it can charge people to receive it. Smart cards are employed to securely hold the decryption keys that allow access to some or all of the content in the stream. This system has been cracked several times, allowing a subset of users free access to the content; however, the satellite TV providers learned from their early mistakes and upgraded new smart cards to correct the old problems. DRM will also become very important in the industry of Software as a

Service (SaaS). Similar to companies that provide satellite TV service, companies that provide SaaS rely on a subscription basis for profitability. If someone could pay for a single license and then distribute that to hundreds of employees, the provider would soon go out of business. Many systems in the past have been cracked because the key was housed inside the software. This has prompted some systems to use specific hardware to store and protect the key. These devices are commonly known as Hardware Security Modules, or HSMs. They are usually designed to protect the key in hardware so that even if the device is tampered with, it will not reveal key material. Smart cards are one example of this technology. Another example is hardware token USB keys that must be inserted into the machine for the software to decrypt and run. Placing the keys in hardware makes an attack to retrieve them much harder, a concept that is employed in the Trusted Platform Module; in fact, one of the primary complaints against the TPM is its inability to enforce DRM restrictions.

Cryptographic Applications

A few applications can be used to encrypt data conveniently on your personal computer. (This is by no means a complete list of every application.) Pretty Good Privacy (PGP) is mentioned in this book because it is a useful protocol suite. Created by Philip Zimmermann in 1991, it passed through several versions that were available for free under a noncommercial license. PGP is now an enterprise encryption product, acquired by the Symantec Corporation in 2010. PGP can be applied to popular e-mail programs to handle the majority of day-to-day encryption tasks using a combination of symmetric and asymmetric encryption protocols. One of the unique features of PGP is its ability to use both symmetric and asymmetric encryption methods, accessing the strengths of each method and avoiding the weaknesses of each as well. Symmetric keys are used for bulk encryption, taking advantage of the speed and efficiency of symmetric encryption. The symmetric keys are passed using asymmetric methods, capitalizing on the flexibility of this method. PGP- based technology is now sold as part of a commercial application, with home and corporate versions.

Cross Check PGP In Chapter 7 you will learn some additional details about PGP. Why is the ability to use asymmetric and symmetric encryption in the same program important?

GnuPG, or Gnu Privacy Guard, is an open source implementation of the OpenPGP standard. This command line–based tool is a public key encryption program designed to protect electronic communications such as e-mail. It operates similarly to PGP and includes a method for managing public/private keys. File system encryption is becoming a standard means of protecting data

while in storage. Even hard drives are available with built-in AES encryption. Microsoft expanded its Encrypting File System (EFS), available since the Windows 2000 operating system, with BitLocker, a

boot-sector encryption method that protects data that was introduced with the Windows Vista operating system. BitLocker is also used in Windows Server 2008 and the Windows 7 and beyond operating systems. BitLocker utilizes AES encryption to encrypt every file on the hard drive automatically. All encryption occurs in the background, and decryption occurs seamlessly when data is requested. The decryption key can be stored in the TPM or on a USB key.

Database Encryption Due partly to increased regulatory concerns and partly to more targeted attacks, databases have begun to offer native support for encryption. Protecting data at rest in the enterprise frequently involves data stored in databases. Building data protection mechanisms into the database systems is not new (it has been around for a long time), but enterprise adoption of this functionality has been slow. Symmetric encryption algorithms such as 3DES and AES are used to encrypt data internally in the database. Protection mechanisms that can be managed by row and by column are included in most major database applications; the challenge is in convincing organizations to use this proven protection methodology. It does add complexity to the system, but in today’s environment of data breaches and corporate espionage, the complexity is easier to manage than the effects of a data loss.

Use of Proven Technologies When setting up a cryptographic scheme, it is important to use proven technologies. Proven cryptographic libraries and proven cryptographically correct random number generators are the foundational elements associated with a solid program. Homegrown or custom elements in these areas can greatly increase risk associated with a broken system. Developing your own cryptographic algorithms is beyond the abilities of most groups. Algorithms are complex and difficult to create. Any algorithm that has not had public review can have weaknesses in the

algorithm. Most good algorithms are approved for use only after a lengthy test and public review phase.

Chapter 5 Review

For More Information Applied Cryptography, Second Edition, Bruce Schneier (John Wiley & Sons)

Cryptool: https://www.cryptool.org/en/

Bruce Schneier Blog: https://www.schneier.com/cryptography.html

Lab Book Exercises The following lab exercises from the companion lab manual, Principles of Computer Security Lab Manual, Fourth Edition, provide practical application of material covered in this chapter:

Chapter Summary After reading this chapter and completing the exercises, you should understand the following about cryptography.

Understand the fundamentals of cryptography

Understand the fundamental methods.

Understand how to compare strengths and performance of algorithms.

Have an appreciation of the historical aspects of cryptography.

Identify and describe the three types of cryptography

Symmetric cryptography is based upon the concept of a shared secret or key.

Asymmetric cryptography is based upon a key that can be made openly available to the public, yet still provide security.

One-way, or hashing, cryptography takes data and enciphers it. However, there is no way to decipher it and no key.

Proper random number generation is essential for cryptographic use, as the strength of the implementation frequently depends upon it being truly random and unknown.

List and describe current cryptographic algorithms

Hashing is the use of a one-way function to generate a message summary for data integrity.

Hashing algorithms include SHA (Secure Hash Algorithm) and MD (Message Digest).

Symmetric encryption is a shared secret form of encrypting data for confidentiality; it is fast and reliable, but needs secure key management.

Symmetric algorithms include DES (Data Encryption Standard), 3DES, AES (Advanced Encryption Standard), CAST, Blowfish, IDEA, and RC (Rivest Cipher) variants.

Asymmetric encryption is a public/private key-pair encryption used for authentication, nonrepudiation, and confidentiality.

Asymmetric algorithms include RSA, Diffie-Hellman, ElGamal, and ECC.

Explain how cryptography is applied for security

Confidentiality is gained because encryption is very good at scrambling information to make it look like random noise, when in fact a key can decipher the message and return it to its original state.

Integrity is gained because hashing algorithms are specifically designed to check integrity. They can reduce a message to a mathematical value that can be independently calculated, guaranteeing that any message alteration would change the mathematical value.

Nonrepudiation is the property of not being able to claim that you did not send the data. This property is gained because of the properties of private keys.

Authentication, or being able to prove you are you, is achieved through the private keys involved in digital signatures.

The use of key generation methods including ephemeral keys and key stretching are important tools in the implementation of strong cryptosystems.

Digital signatures, combining multiple types of encryption, provide an authentication method verified by a third party, allowing you to use them as if you were actually signing the document with your regular signature.

Digital rights management (DRM) uses some form of asymmetric encryption that allows an application to determine if you are an authorized user of the digital content you are trying to access. For example, things like DVDs and certain digital music formats such as AACS use DRM.

The principle of perfect forward secrecy protects future messages from previous message key disclosures.

Proven cryptographic technologies are important as most cryptographic systems fail and only a few stand the test of time. Homebrew systems are ripe for failure.

Cipher suites provide information to assist developers in choosing the correct methods to achieve desired levels of protection.

Key Terms algorithm (96) block cipher (104) ciphertext (94) collision attack (99) confusion (120) cryptanalysis (90) cryptography (90) differential cryptanalysis (91) diffusion (120) digital rights management (121) digital signature (120) entropy (98) ephemeral keys (119) eXclusive OR (XOR) (97) hash (99) key (97) key escrow (118) key management (98) keyspace (93) key stretching (119) linear cryptanalysis (91) multiple encryption (104) perfect forward secrecy (120) plaintext (94) shared secret (103) shift cipher (94)

steganography (114) stream cipher (107) substitution (92) transposition (92) transposition cipher (93) trapdoor function (109) Vigenère cipher (95)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. Making two inputs result in the exact same cryptographic hash is called a(n) _______________.

2. A simple way to hide information, the _______________ moves a letter a set number of places down the alphabet.

3. To provide for perfect forward security, one should use _______________.

4. _______________ is required for symmetric encryption. 5. _______________ is the evaluation of a cryptosystem to test its

security.

6. _______________ refers to every possible value for a cryptographic key.

7. _______________ is the function most commonly seen in cryptography, a “bitwise exclusive” or.

8. The measure of randomness in a data stream is called _______________.

9. Processing through an algorithm more than once with different keys

is called _______________.

10. The basis for symmetric cryptography is the principle of a(n) _______________.

Multiple-Choice Quiz 1. When a message is sent, no matter what its format, why do we care

about its integrity?

A. To ensure proper formatting

B. To show that the encryption keys are undamaged

C. To show that the message has not been edited in transit

D. To show that no one has viewed the message

2. How is 3DES different from many other types of encryption described in this chapter?

A. It only encrypts the hash.

B. It hashes the message before encryption.

C. It uses three keys and multiple encryption and/or decryption sets.

D. It can display the key publicly.

3. If a message has a hash, how does the hash protect the message in transit?

A. If the message is edited, the hash will no longer match.

B. Hashing destroys the message so that it cannot be read by anyone.

C. Hashing encrypts the message so that only the private key holder can read it.

D. The hash makes the message uneditable.

4. What is the biggest drawback to symmetric encryption? A. It is too easily broken.

B. It is too slow to be easily used on mobile devices.

C. It requires a key to be securely shared.

D. It is available only on UNIX.

5. What is Diffie-Hellman most commonly used for? A. Symmetric encryption key exchange

B. Signing digital contracts

C. Secure e-mail

D. Storing encrypted passwords

6. What is public key cryptography a more common name for? A. Asymmetric encryption

B. SHA

C. Symmetric encryption

D. Hashing

7. What algorithm can be used to provide for key stretching? A. PBKDF2

B. SHA356

C. RIPEMD

D. 3DES

8. A good hash function is resistant to what?

A. Brute-forcing

B. Rainbow tables

C. Interception

D. Collisions

9. How is 3DES an improvement over normal DES? A. It uses public and private keys.

B. It hashes the message before encryption.

C. It uses three keys and multiple encryption and/or decryption sets.

D. It is faster than DES.

10. What is the best kind of key to have? A. Easy to remember

B. Long and random

C. Long and predictable

D. Short

Essay Quiz 1. Describe how polyalphabetic substitution works. 2. Explain why asymmetric encryption is called public key encryption. 3. Describe cryptanalysis.

Lab Projects

• Lab Project 5.1 Using a utility program, demonstrate how single character changes can make substantial changes to hash values.

• Lab Project 5.2 Create a keyset and use it to transfer a file securely.

chapter 6 Public Key Infrastructure

Without trust, there is nothing.

—ANONYMOUS

P

In this chapter, you will learn how to

Implement the basics of public key infrastructures

Describe the role of registration authorities

Use digital certificates

Understand the lifecycle of certificates

Explain the relationship between trust and certificate verification

Describe the roles of certificate authorities and certificate repositories

Identify centralized and decentralized infrastructures

Describe public and in-house certificate authorities

ublic key infrastructures (PKIs) are becoming a central security foundation for managing identity credentials in many companies. The technology manages the issue of binding public keys and identities

across multiple applications. The other approach, without PKIs, is to implement many different security solutions and hope for interoperability and equal levels of protection. PKIs comprise several components, including certificates, registration

and certificate authorities, and a standard process for verification. PKIs are about managing the sharing of trust and using a third party to vouch for the trustworthiness of a claim of ownership over a credential document, called a certificate.

The Basics of Public Key Infrastructures A public key infrastructure (PKI) provides all the components necessary for different types of users and entities to be able to communicate securely and in a predictable manner. A PKI is made up of hardware, applications, policies, services, programming interfaces, cryptographic algorithms, protocols, users, and utilities. These components work together to allow

communication to take place using public key cryptography and symmetric keys for digital signatures, data encryption, and integrity.

Cross Check PKIs and Encryption The technologies used in PKI include many cryptographic algorithms and mechanisms. Encryption technologies and public key principles were covered in Chapter 5. A basic understanding of public and private keys and their relationship to public key encryption is a prerequisite for this chapter. If needed, review that material before you attempt the details of PKI in this chapter.

Although many different applications and protocols can provide the same type of functionality, constructing and implementing a PKI boils down to establishing a level of trust. If, for example, John and Diane want to communicate securely, John can generate his own public/private key pair and send his public key to Diane, or he can place his public key in a directory that is available to everyone. If Diane receives John’s public key, either from him or from a public directory, how does she know the key really came from John? Maybe another individual, Katie, is masquerading as John and has replaced John’s public key with her own, as shown in Figure 6.1 (referred to as a man-in-the-middle attack). If this took place, Diane would believe that her messages could be read only by John and that the replies were actually from him. However, she would actually be communicating with Katie. What is needed is a way to verify an individual’s identity, to ensure that a person’s public key is bound to their identity and thus ensure that the previous scenario (and others) cannot take place.

• Figure 6.1 Without PKIs, individuals could spoof others’ identities.

In PKI environments, entities called registration authorities (RAs) and certificate authorities (CAs) provide services similar to those of the Department of Motor Vehicles (DMV). When John goes to register for a driver’s license, he has to prove his identity to the DMV by providing his passport, birth certificate, or other identification documentation. If the DMV is satisfied with the proof John provides (and John passes a driving test), the DMV will create a driver’s license that can then be used by John to prove his identity. Whenever John needs to identify himself, he can show his driver’s license. Although many people may not trust John to identify himself truthfully, they do trust the third party, the DMV. In the PKI context, while some variations exist in specific products, the

RA will require proof of identity from the individual requesting a certificate and will validate this information. The RA will then advise the CA to generate a certificate, which is analogous to a driver’s license. The CA will digitally sign the certificate using its private key. The use of the private key ensures to the recipient that the certificate came from the CA. When Diane receives John’s certificate and verifies that it was actually digitally signed by a CA that she trusts, she will believe that the certificate is actually John’s—not because she trusts John, but because she trusts the entity that is vouching for his identity (the CA).

Tech Tip

Public and Private Keys Recall from Chapter 5 that the public key is the one that you give to others and the private key never leaves your possession. Anything one key does, the other undoes, so if you encrypt something with the public key, only the holder of the private key can decrypt it. If you encrypt something with the private key, then everyone who uses the public key knows that the holder of the private key did the encryption. Certificates do not alter any of this; they only offer a standard means of transferring keys.

This is commonly referred to as a third-party trust model. Public keys are components of digital certificates, so when Diane verifies the CA’s digital signature, this verifies that the certificate is truly John’s and that the public key the certificate contains is also John’s. This is how John’s identity is bound to his public key. This process allows John to authenticate himself to Diane and others.

Using the third-party certificate, John can communicate with Diane, using public key encryption, without prior communication or a preexisting relationship. Once Diane is convinced of the legitimacy of John’s public key, she can

use it to encrypt messages between herself and John, as illustrated in Figure 6.2.

• Figure 6.2 Public keys are components of digital certificates.

Numerous applications and protocols can generate public/private key pairs and provide functionality similar to what a PKI provides, but no trusted third party is available for both of the communicating parties. For each party to choose to communicate this way without a third party vouching for the other’s identity, the two must choose to trust each other

and the communication channel they are using. In many situations, it is impractical and dangerous to arbitrarily trust an individual you do not know, and this is when the components of a PKI must fall into place—to provide the necessary level of trust you cannot, or choose not to, provide on your own.

Exam Tip: PKIs are composed of several elements:

• Certificates (containing keys)

• Certificate authorities (CAs) • Registration authorities (RAs) • Certificate revocation lists (CRLs) • Trust models

What does the “infrastructure” in “public key infrastructure” really mean? An infrastructure provides a sustaining groundwork upon which other things can be built. So an infrastructure works at a low level to provide a predictable and uniform environment that allows other, higher- level technologies to work together through uniform access points. The environment that the infrastructure provides allows these higher-level applications to communicate with each other and gives them the underlying tools to carry out their tasks.

Certificate Authorities A certificate authority (CA) is a trusted authority that certifies individuals’ identities and creates electronic documents indicating that individuals are who they say they are. The electronic document is referred to as a digital certificate, and it establishes an association between the subject’s identity and a public key. The private key that is paired with the public key in the certificate is stored separately.

As noted in Chapter 5, it is important to safeguard the private key. Typically, it should never leave the machine or device where it was created.

A CA is more than just a piece of software, however; it is actually made up of the software, hardware, procedures, policies, and people who are involved in validating individuals’ identities and generating the certificates. This means that if one of these components is compromised, it can negatively affect the CA overall and can threaten the integrity of the certificates it produces.

Cross Check Certificates Stored on a Client PC Certificates are stored on user PCs. Chapter 17 covers the use of the Internet and associated materials, including the use of certificates by web browsers. Take a moment to explore the certificates stored on your PC by your browser. To understand the details behind how certificates are stored and managed, the reader is directed to the details in Chapter 17.

Every CA should have a certification practices statement (CPS) that outlines how identities are verified; the steps the CA follows to generate, maintain, and transmit certificates; and why the CA can be trusted to fulfill its responsibilities. The CPS describes how keys are secured, what data is placed within a

digital certificate, and how revocations will be handled. If a company is going to use and depend on a public CA, the company’s security officers, administrators, and legal department should review the CA’s entire CPS to ensure that it will properly meet the company’s needs, and to make sure that the level of security claimed by the CA is high enough for their use and environment. A critical aspect of a PKI is the trust between the users and the CA, so the CPS should be reviewed and understood to ensure that

this level of trust is warranted. The certificate server is the actual service that issues certificates based

on the data provided during the initial registration process. The server constructs and populates the digital certificate with the necessary information and combines the user’s public key with the resulting certificate. The certificate is then digitally signed with the CA’s private key.

Tech Tip

Trusting CAs The question of whether a CA can be trusted is part of the continuing debate on how much security PKIs actually provide. Overall, people put a lot of faith in CAs. The companies that provide CA services understand this and also understand that their business is based on their reputation. If a CA was compromised or did not follow through on its various responsibilities, word would get out and it would quickly lose customers and business. CAs work diligently to ensure that the reputation of their products and services remains good by implementing very secure facilities, methods, procedures, and personnel. But it is up to the company or individual to determine what degree of trust can actually be given and what level of risk is acceptable.

Registration Authorities A registration authority (RA) is the PKI component that accepts a request for a digital certificate and performs the necessary steps of registering and authenticating the person requesting the certificate. The authentication requirements differ depending on the type of certificate being requested. Most CAs offer a series of classes of certificates with increasing trust by class. The specific classes are described in the upcoming Tech Tip sidebar, “Certificate Classes.” Each higher class of certificate can carry out more powerful and critical

tasks than the one below it. This is why the different classes have different requirements for proof of identity. If you want to receive a Class 1

certificate, you may only be asked to provide your name, e-mail address, and physical address. For a Class 2 certification, you may need to provide the RA with more data, such as your driver’s license, passport, and company information, that can be verified. To obtain a Class 3 certificate, you will be asked to provide even more information and most likely will need to go to the RA’s office for a face-to-face meeting. Each CA will outline the certification classes it provides and the identification requirements that must be met to acquire each type of certificate.

Tech Tip

Certificate Classes The types of certificates available can vary between different CAs, but usually at least three different types are available, and they are referred to as classes:

Class 1 A Class 1 certificate is usually used to verify an individual’s identity through e- mail. A person who receives a Class 1 certificate can use his public/private key pair to digitally sign e-mail and encrypt message contents.

Class 2 A Class 2 certificate can be used for software signing. A software vendor would register for this type of certificate so that it could digitally sign its software. This provides integrity for the software after it is developed and released, and it allows the receiver of the software to verify from where the software actually came.

Class 3 A Class 3 certificate can be used by a company to set up its own CA, which will allow it to carry out its own identification verification and generate certificates internally.

In most situations, when a user requests a Class 1 certificate, the registration process will require the user to enter specific information into a web-based form. The web page will have a section that accepts the user’s public key, or it will step the user through creating a public/private key pair, which will allow the user to choose the size of the keys to be created. Once these steps have been completed, the public key is attached to the certificate registration form and both are forwarded to the RA for processing. The RA is responsible only for the registration process and cannot actually generate a certificate. Once the RA is finished processing

the request and verifying the individual’s identity, the RA sends the request to the CA. The CA uses the RA-provided information to generate a digital certificate, integrates the necessary data into the certificate fields (user identification information, public key, validity dates, proper use for the key and certificate, and so on), and sends a copy of the certificate to the user. These steps are shown in Figure 6.3. The certificate may also be posted to a publicly accessible directory so that others can access it.

• Figure 6.3 Steps for obtaining a digital certificate

Note that a 1:1 correspondence does not necessarily exist between identities and certificates. An entity can have multiple key pairs, using separate public keys for separate purposes. Thus, an entity can have multiple certificates, each attesting to separate public key ownership. It is also possible to have different classes of certificates, again with different keys. This flexibility allows entities total discretion in how they manage their keys, and the PKI manages the complexity by using a unified process that allows key verification through a common interface. If an application creates a key store that can be accessed by other

applications, it will provide a standardized interface, called the application programming interface (API). As an example, Figure 6.4 shows that application A went through the process of registering a certificate and generating a key pair. It created a key store that provides an interface to allow other applications to communicate with it and use the items held within the store. The local key store is just one location where these items can be held.

Often the digital certificate and public key are also stored in a certificate repository (as discussed in the “Certificate Repositories” section of this chapter) so that it is available to a subset of individuals.

• Figure 6.4 Some key stores can be shared by different applications.

Exam Tip: The RA verifies the identity of the certificate requestor on behalf of the CA. The CA generates the certificate using information forwarded by the RA.

Local Registration Authorities A local registration authority (LRA) performs the same functions as an

RA, but the LRA is closer to the end users. This component is usually implemented in companies that have their own internal PKIs and have distributed sites. Each site has users that need RA services, so instead of requiring them to communicate with one central RA, each site can have its own LRA. This reduces the amount of traffic that would be created by several users making requests across wide area network (WAN) lines. The LRA performs identification, verification, and registration functions. It then sends the request, along with the user’s public key, to a centralized CA so that the certificate can be generated. It acts as an interface between the users and the CA. LRAs simplify the RA/CA process for entities that desire certificates only for in-house use.

Tech Tip

Sharing Key Stores Different applications from the same vendor may share key stores. Microsoft applications keep user keys and certificates in a Registry entry within that user’s profile. The applications can then save and retrieve them from this single location or key store. Other applications could also use the same keys if they knew where they were stored by using Registry API calls.

Digital Certificates A digital certificate binds an individual’s identity to a public key, and it contains all the information a receiver needs to be assured of the identity of the public key owner. After an RA verifies an individual’s identity, the CA generates the digital certificate, but how does the CA know what type of data to insert into the certificate? The certificates are created and formatted based on the X.509 standard,

which outlines the necessary fields of a certificate and the possible values that can be inserted into the fields. As of this writing, X.509 version 3 is the most current version of the standard. X.509 is a standard of the International Telecommunication Union (www.itu.int). The IETF’s Public

Key Infrastructure (X.509), or PKIX, working group has adapted the X.509 standard to the more flexible organization of the Internet, as specified in RFC 5280, and is commonly referred to as PKIX for Public Key Infrastructure X.509. Table 6.1 lists and describes the fields in an X.509 certificate.

Table 6.1 X.509 Certificate Fields

Figure 6.5 shows the actual values of the different certificate fields for a particular certificate in Internet Explorer. The version of this certificate is V3 (X.509 v3) and the serial number is also listed—this number is unique for each certificate that is created by a specific CA. The CA used the MD5 hashing algorithm to create the message digest value and then signed it using the CA’s private key using the RSA algorithm. The actual CA that issued the certificate is Root SGC Authority, and the valid dates indicate how long this certificate is valid. The subject is MS SGC Authority, which is the entity that registered this certificate and that is bound to the embedded public key. The actual public key is shown in the lower window and is represented in hexadecimal.

• Figure 6.5 Fields within a digital certificate

The subject of a certificate is commonly a person, but it does not have to be. The subject can also be a network device (router, web server, firewall, and so on), an application, a department, or a company. Each has its own identity that needs to be verified and proven to another entity before secure, trusted communication can be initiated. If a network device is using a certificate for authentication, the certificate may contain the identity of that device. This allows a user of the device to verify its authenticity based on the signed certificate and trust in the signing authority. This trust can be transferred to the identity of the device indicating authenticity.

Tech Tip

X.509 Digital Certificate Extensions Following are some key examples of certificate extensions:

DigitalSignature The key used to verify a digital signature

KeyEncipherment The key used to encrypt other keys used for secure key distribution

DataEncipherment The key used to encrypt data, which cannot be used to encrypt other keys

CRLSign The key used to verify a CA signature on a CRL

KeyCertSign The key used to verify CA signatures on certificates

NonRepudiation The key used when a nonrepudiation service is being provided

Certificate Extensions Certificate extensions allow for further information to be inserted within the certificate, which can be used to provide more functionality in a PKI implementation. Certificate extensions can be standard or private. Standard certificate extensions are implemented for every PKI

implementation. Private certificate extensions are defined for specific organizations (or domains within one organization), and they allow companies to further define different, specific uses for digital certificates to best fit their business needs. Several different extensions can be implemented, one being key usage

extensions, which dictate how the public key that is held within the certificate can be used. Remember that public keys can be used for different functions: symmetric key encryption, data encryption, verifying digital signatures, and more. A nonrepudiation service can be provided by a third-party notary. In this

situation, the sender’s digital signature is verified and then signed by the notary so that the sender cannot later deny signing and sending the message. This is basically the same function performed by a traditional notary using paper—validate the sender’s identity and validate the time and date of an item being signed and sent. This is required when the receiver needs to be really sure of the sender’s identity and wants to be legally protected against possible fraud or forgery. If a company needs to be sure that accountable nonrepudiation services

will be provided, a trusted time source needs to be used, which can be a trusted third party called a time stamp authority (TSA). Using a trusted time source gives users a higher level of confidence as to when specific messages were digitally signed. For example, suppose Barry sends Ron a message and digitally signs it, and Ron later civilly sues Barry over a dispute. This digitally signed message may be submitted by Ron as evidence pertaining to an earlier agreement that Barry now is not fulfilling. If a trusted time source was not used in their PKI environment, Barry could claim that his private key had been compromised before that message was sent. If a trusted time source was implemented, then it could be shown that the message was signed before the date on which Barry claims his key was compromised. If a trusted time source is not used, no activity that was carried out within a PKI environment can be truly proven because it is so easy to change system and software time settings.

Tech Tip

Critical Flag and Certificate Usage When an extension is marked as critical, it means that the CA is certifying the key for only that specific purpose. If Joe receives a certificate with a DigitalSignature key usage extension and the critical flag is set, Joe can use the public key only within that certificate to validate digital signatures, and no more. If the extension was marked as noncritical, the key can be used for purposes outside of those listed in the extensions, so in this case it is up to Joe (and his applications) to decide how the key will be used.

Critical and Noncritical Extensions Certificate extensions are considered either critical or noncritical, which is indicated by a specific flag within the certificate itself. When this flag is set to critical, it means that the extension must be understood and processed by the receiver. If the receiver is not configured to understand a particular extension marked as critical, and thus cannot process it properly, the certificate cannot be used for its proposed purpose. If the flag does not indicate that the extension is critical, the certificate can be used for the intended purpose, even if the receiver does not process the appended extension.

Certificate Attributes Four main types of certificates are used:

End-entity certificates

CA certificates

Cross-certification certificates

Policy certificates

End-entity certificates are issued by a CA to a specific subject, such as

Joyce, the Accounting department, or a firewall, as illustrated in Figure 6.6. An end-entity certificate is the identity document provided by PKI implementations.

• Figure 6.6 End-entity and CA certificates

A CA certificate can be self-signed, in the case of a standalone or root CA, or it can be issued by a superior CA within a hierarchical model. In the model in Figure 6.6, the superior CA gives the authority and allows the subordinate CA to accept certificate requests and generate the individual certificates itself. This may be necessary when a company needs to have multiple internal CAs, and different departments within an organization need to have their own CAs servicing their specific end-entities in their sections. In these situations, a representative from each department requiring a CA registers with the higher trusted CA and requests a Certificate Authority certificate. (Public and private CAs are discussed in the “Public Certificate Authorities” and “In-House Certificate Authorities” sections later in this chapter, as are the different trust models that are available for companies.) A cross-certification certificate, or cross-certificate, is used when

independent CAs establish peer-to-peer trust relationships. Simply put, cross-certificates are a mechanism through which one CA can issue a certificate allowing its users to trust another CA. Within sophisticated CAs used for high-security applications, a

mechanism is required to provide centrally controlled policy information to PKI clients. This is often done by placing the policy information in a policy certificate.

Certificate Lifecycles Keys and certificates should have lifetime settings that force the user to register for a new certificate after a certain amount of time. Determining the proper length of these lifetimes is a trade-off: shorter lifetimes limit the ability of attackers to crack them, but longer lifetimes lower system overhead. More-sophisticated PKI implementations perform automated and often transparent key updates to avoid the time and expense of having users register for new certificates when old ones expire.

This means that the certificate and key pair has a lifecycle that must be managed. Certificate management involves administrating and managing each of these phases, including registration, certificate and key generation, renewal, and revocation. Additional management functions include CRL distribution, certificate suspension, and key destruction.

Setting certificate lifetimes way into the future and using them for long periods of time provides attackers with extended windows to attack the cryptography. As stated in Chapter 5, cryptography merely buys time against an attacker; it is never an absolute guarantee.

Registration and Generation A key pair (public and private keys) can be generated locally by an application and stored in a local key store on the user’s workstation. The key pair can also be created by a central key-generation server, which will require secure transmission of the keys to the user. The key pair that is created on the centralized server can be stored on the user’s workstation or on the user’s smart card, which will allow for more flexibility and mobility. The act of verifying that an individual indeed has the corresponding

private key for a given public key is referred to as proof of possession. Not all public/private key pairs can be used for digital signatures, so asking the individual to sign a message and return it to prove that she has the necessary private key will not always work. If a key pair is used for encryption, the RA can send a challenge value to the individual, who, in turn, can use her private key to encrypt that value and return it to the RA. If the RA can successfully decrypt this value with the public key that was provided earlier, the RA can be confident that the individual has the necessary private key and can continue through the rest of the registration phase.

Key regeneration and replacement is usually done to protect against these types of threats, although as the processing power of computers increases and our knowledge of cryptography and new possible cryptanalysis-based attacks expands, key lifetimes may drastically decrease. As with everything within the security field, it is better to be safe now than to be surprised later and sorry.

Exam Tip: Good key management and proper key replacement intervals protect keys from being compromised through human error. Choosing a large key size makes a brute-force attack more difficult.

The PKI administrator usually configures the minimum required key size that users must use to have a key generated for the first time, and then for each renewal. In most applications, there is a drop-down list of possible algorithms to choose from, and possible key sizes. The key size should provide the necessary level of security for the current environment. The lifetime of the key should be long enough that continual renewal will not negatively affect productivity, but short enough to ensure that the key cannot be successfully compromised.

Tech Tip

Centralized vs. Local Key Generation In most modern PKI implementations, users have two key pairs. One key pair is often generated by a central server and used for encryption and key transfers. This allows the corporate PKI to retain a copy of the encryption key pair for recovery, if necessary. The second key pair, a digital signature key pair, is usually generated by the user to make sure that she is the only one with a copy of the private key. Nonrepudiation can be challenged if there is any doubt about someone else obtaining a copy of an individual’s signature private key. If the key pair was created on a centralized server, that could weaken the case that the individual was the only one who had a copy of her private key. If a copy of a user’s signature private key is stored anywhere other than in her possession, or if there is a possibility of someone obtaining the user’s key, then true nonrepudiation cannot be provided.

CSR A certificate signing request (CSR) is the actual request to a CA containing a public key and the requisite information needed to generate a certificate. The CSR contains all of the identifying information that is to be bound to the key by the certificate generation process.

Renewal The certificate itself has its own lifetime, which can be different from the key pair’s lifetime. The certificate’s lifetime is specified by the validity dates inserted into the digital certificate. These are beginning and ending dates indicating the time period during which the certificate is valid. The certificate cannot be used before the start date, and once the end date is met, the certificate is expired and a new certificate will need to be issued. A renewal process is different from the registration phase in that the RA

assumes that the individual has already successfully completed one registration round. If the certificate has not actually been revoked, the original keys and certificate can be used to provide the necessary authentication information and proof of identity for the renewal phase. The certificate may or may not need to change during the renewal

process; this usually depends on why the renewal is taking place. If the certificate just expired and the keys will still be used for the same purpose, a new certificate can be generated with new validity dates. If, however, the key pair functionality needs to be expanded or restricted, new attributes and extensions may need to be integrated into the new certificate. These new functionalities may require more information to be gathered from the individual renewing the certificate, especially if the class changes or the new key uses allow for more powerful abilities. This renewal process is required when the certificate has fulfilled its

lifetime and its end validity date has been met.

Suspension When the owner of a certificate wishes to mark a certificate as no longer valid prior to its natural expiration, two choices exist: revocation and suspension. Revocation, discussed in the next section, is an action with a permanent outcome. Instead of being revoked, a certificate can be suspended, meaning it is temporarily put on hold. If, for example, Bob is taking an extended vacation and wants to ensure that his certificate will not be compromised or used during that time, he can make a suspension request to the CA. The CRL would list this certificate and its serial number, and in the field that describes why the certificate is revoked, it would instead indicate a hold state. Once Bob returns to work, he can make a request to the CA to remove his certificate from the list.

Exam Tip: A certificate suspension can be a useful process tool while investigating whether or not a certificate should be considered to be valid.

Another reason to suspend a certificate is if an administrator is suspicious that a private key might have been compromised. While the issue is under investigation, the certificate can be suspended to ensure that it cannot be used.

Relying on an expiration date on a certificate to “destroy” the utility of a key will not work. A new certificate can be issued with an “extended date.” To end the use of a key set, an entry in a CRL is the only sure way to prevent reissuance and re-dating of a certificate.

Revocation

A certificate can be revoked when its validity needs to be ended before its actual expiration date is met, and this can occur for many reasons: for example, a user may have lost a laptop or a smart card that stored a private key; an improper software implementation may have been uncovered that directly affected the security of a private key; a user may have fallen victim to a social engineering attack and inadvertently given up a private key; data held within the certificate may no longer apply to the specified individual; or perhaps an employee left a company and should not be identified as a member of an in-house PKI any longer. In the last instance, the certificate, which was bound to the user’s key pair, identified the user as an employee of the company, and the administrator would want to ensure that the key pair could not be used in the future to validate this person’s affiliation with the company. Revoking the certificate does this.

Once revoked, a certificate cannot be reinstated. This is to prevent an unauthorized reinstatement by someone who has unauthorized access to the key(s). A key pair can be reinstated for use by issuing a new certificate if at a later time the keys are found to be secure. The old certificate would still be void, but the new one would be valid.

If any of these things happens, a user’s private key has been compromised or should no longer be mapped to the owner’s identity. A different individual may have access to that user’s private key and could use it to impersonate and authenticate as the original user. If the impersonator used the key to digitally sign a message, the receiver would verify the authenticity of the sender by verifying the signature by using the original user’s public key, and the verification would go through perfectly —the receiver would believe it came from the proper sender and not the impersonator. If receivers could look at a list of certificates that had been revoked before verifying the digital signature, however, they would know not to trust the digital signatures on the list. Because of issues associated with the private key being compromised, revocation is permanent and final

—once revoked, a certificate cannot be reinstated. If reinstatement was allowed and a user revoked his certificate, then the unauthorized holder of the private key could use it to restore the certificate validity.

Exam Tip: A certificate cannot be assumed to be valid without checking for revocation before each use.

Certificate Revocation List The CA provides protection against impersonation and similar fraud by maintaining a certificate revocation list (CRL), a list of serial numbers of certificates that have been revoked. The CRL also contains a statement indicating why the individual certificates were revoked and a date when the revocation took place. The list usually contains all certificates that have been revoked within the lifetime of the CA. Certificates that have expired are not the same as those that have been revoked. If a certificate has expired, it means that its end validity date was reached. The format of the CRL message is also defined by X.509. The list is signed, to prevent tampering, and contains information on certificates that have been revoked and the reasons for their revocation. These lists can grow quite long, and as such, there are provisions for date timestamping the list and for issuing delta lists, which show changes since the last list was issued.

Tech Tip

CRL Reason Codes Per the X.509 v2 CRL standard, the following reasons for revocation are used:

The CA is the entity that is responsible for the status of the certificates it generates; it needs to be told of a revocation, and it must provide this information to others. The CA is responsible for maintaining the CRL and posting it in a publicly available directory.

Exam Tip: The certificate revocation list is an essential item to ensure a certificate is still valid. CAs post CRLs in publicly available directories to permit automated checking of certificates against the list before certificate use by a client. A user should never trust a certificate that has not been checked against the appropriate CRL.

We need to have some system in place to make sure people cannot

arbitrarily have others’ certificates revoked, whether for revenge or for malicious purposes. When a revocation request is submitted, the individual submitting the request must be authenticated. Otherwise, this could permit a type of denial-of-service attack, in which someone has another person’s certificate revoked. The authentication can involve an agreed-upon password that was created during the registration process, but authentication should not be based on the individual proving that he has the corresponding private key, because it may have been stolen, and the CA would be authenticating an imposter. The CRL’s integrity needs to be protected to ensure that attackers

cannot modify data pertaining to a revoked certification on the list. If this were allowed to take place, anyone who stole a private key could just delete that key from the CRL and continue to use the private key fraudulently. The integrity of the list also needs to be protected to ensure that bogus data is not added to it. Otherwise, anyone could add another person’s certificate to the list and effectively revoke that person’s certificate. The only entity that should be able to modify any information on the CRL is the CA. The mechanism used to protect the integrity of a CRL is a digital

signature. The CA’s revocation service creates a digital signature for the CRL, as shown in Figure 6.7. To validate a certificate, the user accesses the directory where the CRL is posted, downloads the list, and verifies the CA’s digital signature to ensure that the proper authority signed the list and to ensure that the list was not modified in an unauthorized manner. The user then looks through the list to determine whether the serial number of the certificate that he is trying to validate is listed. If the serial number is on the list, the private key should no longer be trusted, and the public key should no longer be used. This can be a cumbersome process, so it has been automated in several ways, which are described in the next section.

• Figure 6.7 The CA digitally signs the CRL to protect its integrity.

One concern is how up-to-date the CRL is—how often is it updated and does it actually reflect all the certificates currently revoked? The actual frequency with which the list is updated depends upon the CA and its certification practices statement (CPS). It is important that the list is updated in a timely manner so that anyone using the list has the most current information.

CRL Distribution CRL files can be requested by individuals who need to verify and validate a newly received certificate, or the files can be periodically pushed down

(sent) to all users participating within a specific PKI. This means the CRL can be pulled (downloaded) by individual users when needed or pushed down to all users within the PKI on a timed interval. The actual CRL file can grow substantially, and transmitting this file

and requiring PKI client software on each workstation to save and maintain it can use a lot of resources, so the smaller the CRL is, the better. It is also possible to first push down the full CRL and subsequently push down only delta CRLs, which contain only the changes to the original or base CRL. This can greatly reduce the amount of bandwidth consumed when updating CRLs.

Tech Tip

Authority Revocation Lists In some PKI implementations, a separate revocation list is maintained for CA keys that have been compromised or should no longer be trusted. This list is known as an authority revocation list (ARL). In the event that a CA’s private key is compromised or a cross- certification is cancelled, the relevant certificate’s serial number is included in the ARL. A client can review an ARL to make sure the CA’s public key can still be trusted.

In implementations where the CRLs are not pushed down to individual systems, the users’ PKI software needs to know where to look for the posted CRL that relates to the certificate it is trying to validate. The certificate might have an extension that points the validating user to the necessary CRL distribution point. The network administrator sets up the distribution points, and one or more points can exist for a particular PKI. The distribution point holds one or more lists containing the serial numbers of revoked certificates, and the user’s PKI software scans the list(s) for the serial number of the certificate the user is attempting to validate. If the serial number is not present, the user is assured that it has not been revoked. This approach helps point users to the right resource and also reduces the amount of information that needs to be scanned when checking that a certificate has not been revoked.

Online Certificate Status Protocol (OCSP) One last option for checking distributed CRLs is an online service. When a client user needs to validate a certificate and ensure that it has not been revoked, he can communicate with an online service that will query the necessary CRLs available within the environment. This service can query the lists for the client instead of pushing down the full CRL to each and every system. So if Joe receives a certificate from Stacy, he can contact an online service and send to it the serial number listed in the certificate Stacy sent. The online service would query the necessary CRLs and respond to Joe, indicating whether or not that serial number was listed as being revoked. One of the protocols used for online revocation services is the Online

Certificate Status Protocol (OCSP), a request and response protocol that obtains the serial number of the certificate that is being validated and reviews revocation lists for the client. The protocol has a responder service that reports the status of the certificate back to the client, indicating whether it has been revoked, is valid, or has an unknown status. This protocol and service saves the client from having to find, download, and process the right lists.

Exam Tip: Certificate revocation checks are done either by examining the CRL or by using OCSP to see if a certificate has been revoked.

Key Destruction Key pairs and certificates have set lifetimes, meaning that they will expire at some specified time. It is important that the certificates and keys are properly destroyed when that time comes, wherever the keys are stored (on users’ workstations, centralized key servers, USB token devices, smart cards, and so on).

Tech Tip

Historical Retention of Certificates Note that in modern PKIs, encryption key pairs usually must be retained long after they expire so that users can decrypt information that was encrypted with the old keys. For example, if Bob encrypts a document using his current key and the keys are updated three months later, Bob’s software must maintain a copy of the old key so he can still decrypt the document. In the PKI world, this issue is referred to as key history maintenance.

The goal is to make sure that no one can gain access to a key after its lifetime has ended and use that key for malicious purposes. An attacker might use the key to digitally sign or encrypt a message with the hopes of tricking someone else about his identity (this would be an example of a man-in-the middle attack). Also, if the attacker is performing some type of brute-force attack on your cryptosystem, trying to figure out specific keys that were used for encryption processes, obtaining an old key could give him more insight into how your cryptosystem generates keys. The less information you supply to potential hackers, the better.

Certificate Repositories Once the requestor’s identity has been proven, a certificate is registered with the public side of the key pair provided by the requestor. Public keys must be available to anybody who requires them to communicate within a PKI environment. These keys, and their corresponding certificates, are usually held in a publicly available repository. Certificate repository is a general term that describes a centralized directory that can be accessed by a subset of individuals. The directories are usually Lightweight Directory Access Protocol (LDAP)–compliant, meaning that they can be accessed and searched via an LDAP query from an LDAP client. When an individual initializes communication with another, the sender

can send her certificate and public key to the receiver, which will allow the

receiver to communicate with the sender using encryption or digital signatures (or both) without needing to track down the necessary public key in a certificate repository. This is equivalent to the sender saying, “If you would like to encrypt any future messages you send to me, or if you would like the ability to verify my digital signature, here are the necessary components.” But if a person wants to encrypt the first message sent to the receiver, the sender needs to find the receiver’s public key in a certificate repository.

Cross Check Certificates and Keys Certificates are a standardized method of exchanging asymmetric key information. To understand the need for certificates, you should first be able to answer the questions:

What do I need a public key for?

How can I get someone’s public key, and how do I know it is theirs?

For a refresher on how public and private keys come into play with encryption and digital signatures, refer to Chapter 5.

A certificate repository is a holding place for individuals’ certificates and public keys that are participating in a particular PKI environment. The security requirements for repositories themselves are not as high as those needed for actual CAs and for the equipment and software used to carry out CA functions. Since each certificate is digitally signed by the CA, if a certificate stored in the certificate repository is modified, the recipient will be able to detect this change and know not to accept the certificate as valid.

Trust and Certificate Verification We need to use a PKI if we do not automatically trust individuals we do not know. Security is about being suspicious and being safe, so we need a

third party that we do trust to vouch for the other individual before confidence can be instilled and sensitive communication can take place. But what does it mean that we trust a CA, and how can we use this to our advantage? When a user chooses to trust a CA, she will download that CA’s digital

certificate and public key, which will be stored on her local computer. Most browsers have a list of CAs configured to be trusted by default, so when a user installs a new web browser, several of the most well-known and most trusted CAs will be trusted without any change of settings. An example of this listing is shown in Figure 6.8.

• Figure 6.8 Browsers have a long list of CAs configured to be trusted by default.

In the Microsoft CAPI environment, the user can add and remove CAs from this list as needed. In production environments that require a higher degree of protection, this list will be pruned, and possibly the only CAs listed will be the company’s internal CAs. This ensures that digitally signed software will be automatically installed only if it was signed by the company’s CA. Other products, such as Entrust, use centrally controlled policies to determine which CAs are to be trusted, instead of expecting the user to make these critical decisions.

Tech Tip

Distinguished Names A distinguished name is a label that follows the X.500 standard. This standard defines a naming convention that can be employed so that each subject within an organization has a unique name. An example is {Country = US, Organization = Real Secure, Organizational Unit = R&D, Location = Washington}. CAs use distinguished names to identify the owners of specific certificates.

A number of steps are involved in checking the validity of a message. Suppose, for example, that Maynard receives a digitally signed message from Joyce, who he does not know or trust. Joyce has also included her digital certificate with her message, which has her public key embedded within it. Before Maynard can be sure of the authenticity of this message, he has some work to do. The steps are illustrated in Figure 6.9.

• Figure 6.9 Steps for verifying the authenticity and integrity of a certificate

First, Maynard sees which CA signed Joyce’s certificate and compares it to the list of CAs he has configured within his computer. He trusts the CAs in his list and no others. (If the certificate was signed by a CA that he does not have in the list, he would not accept the certificate as being valid, and thus he could not be sure that this message was actually sent from Joyce or that the attached key was actually her public key.)

Because certificates produce chains of trust, having an unnecessary certificate in your certificate store could lead to trust problems. Best practices indicate that you should understand the certificates in your store, and the need for each. When in doubt, remove it. If it is needed, you can add it back later.

Maynard sees that the CA that signed Joyce’s certificate is indeed in his list of trusted CAs, so he now needs to verify that the certificate has not been altered. Using the CA’s public key and the digest of the certificate, Maynard can verify the integrity of the certificate. Then Maynard can be assured that this CA did actually create the certificate, so he can now trust the origin of Joyce’s certificate. The use of digital signatures allows certificates to be saved in public directories without the concern of them being accidentally or intentionally altered. If a user extracts a certificate from a repository and creates a message digest value that does not match the digital signature embedded within the certificate itself, that user will know that the certificate has been modified by someone other than the CA, and he will know not to accept the validity of the corresponding public key. Similarly, an attacker could not create a new message digest, encrypt it, and embed it within the certificate because he would not have access to the CA’s private key.

But Maynard is not done yet. He needs to be sure that the issuing CA has not revoked this certificate. The certificate also has start and stop dates, indicating a time during which the certificate is valid. If the start date hasn’t happened yet or the stop date has been passed, the certificate is not valid. Maynard reviews these dates to make sure the certificate is still deemed valid. Another step Maynard may go through is to check whether this

certificate has been revoked for any reason. To do so, he will refer to the certificate revocation list (CRL) to see if Joyce’s certificate is listed. He could check the CRL directly with the CA that issued the certificate or via a specialized online service that supports the Online Certificate Status Protocol (OCSP). (Certificate revocation and list distribution were explained in the “Certificate Lifecycles” section, earlier in this chapter.)

Tech Tip

Validating a Certificate The following steps are required for validating a certificate:

1. Compare the CA that digitally signed the certificate to a list of CAs that have already been loaded into the receiver’s computer.

2. Calculate a message digest for the certificate. 3. Use the CA’s public key to decrypt the digital signature and recover what is claimed to be

the original message digest embedded within the certificate (validating the digital signature).

4. Compare the two resulting message digest values to ensure the integrity of the certificate. 5. Review the identification information within the certificate, such as the e-mail address. 6. Review the validity dates. 7. Check a revocation list to see if the certificate has been revoked.

Maynard now trusts that this certificate is legitimate and that it belongs to Joyce. Now what does he need to do? The certificate holds Joyce’s public key, which he needs to validate the digital signature she appended to her message, so Maynard extracts Joyce’s public key from her

certificate, runs her message through a hashing algorithm, and calculates a message digest value of X. He then uses Joyce’s public key to decrypt her digital signature (remember that a digital signature is just a message digest encrypted with a private key). This decryption process provides him with another message digest of value Y. Maynard compares values X and Y, and if they are the same, he is assured that the message has not been modified during transmission. Thus he has confidence in the integrity of the message. But how does Maynard know that the message actually came from Joyce? Because he can decrypt the digital signature using her public key, which indicates that only the associated private key could have been used. There is a miniscule risk that someone could create an identical key pair, but given the enormous keyspace for public keys, this is impractical. The public key can only decrypt something that was encrypted with the related private key, and only the owner of the private key is supposed to have access to it. Maynard can be sure that this message came from Joyce. After all of this he reads her message, which says, “Hi. How are you?”

All of that work just for this message? Maynard’s blood pressure would surely go through the roof if he had to do all of this work only to end up with a short and not very useful message. Fortunately, all of this PKI work is performed without user intervention and happens behind the scenes. Maynard didn’t have to exert any energy. He simply replies, “Fine. How are you?”

Centralized and Decentralized Infrastructures Keys used for authentication and encryption within a PKI environment can be generated in a centralized or decentralized manner. In a decentralized approach, software on individual computers generates and stores cryptographic keys local to the systems themselves. In a centralized infrastructure, the keys are generated and stored on a central server, and the keys are transmitted to the individual systems as needed. You might choose one type over the other for several reasons. If a company uses an asymmetric algorithm that is resource-intensive to

generate the public/private key pair, and if large (and resource-intensive) key sizes are needed, then the individual computers may not have the necessary processing power to produce the keys in an acceptable fashion. In this situation, the company can choose a centralized approach in which a very high-end server with powerful processing abilities is used, probably along with a hardware-based random number generator. Central key generation and storage offers other benefits as well. For

example, it is much easier to back up the keys and implement key recovery procedures with central storage than with a decentralized approach. Implementing a key recovery procedure on each and every computer holding one or more key pairs is difficult, and many applications that generate their own key pairs do not usually interface well with a centralized archive system. This means that if a company chooses to allow its individual users to create and maintain their own key pairs on their separate workstations, no real key recovery procedure can be put in place. This puts the company at risk. If an employee leaves the organization or is unavailable for one reason or another, the company may not be able to access its own business information that was encrypted by that employee. So a centralized approach seems like the best approach, right? Well, the

centralized method has some drawbacks to consider, too. Secure key distribution is a tricky event. This can be more difficult than it sounds. A technology needs to be employed that will send the keys in an encrypted manner, ensure the keys’ integrity, and make sure that only the intended user is receiving the key. Also, the server that centrally stores the keys needs to be highly

available and is a potential single point of failure, so some type of fault tolerance or redundancy mechanism may need to be put into place. If that one server goes down, users could not access their keys, which might prevent them from properly authenticating to the network, resources, and applications. Also, since all the keys are in one place, the server is a prime target for an attacker—if the central key server is compromised, the whole environment is compromised. One other issue pertains to how the keys will actually be used. If a

public/private key pair is being generated for digital signatures, and if the company wants to ensure that it can be used to provide true authenticity and nonrepudiation, the keys should not be generated at a centralized server. This would introduce doubt that only the one person had access to a specific private key. It is better to generate end-user keys on a local machine to eliminate doubt about who did the work and “owns” the keys. If a company uses smart cards to hold users’ private keys, each private

key often has to be generated on the card itself and cannot be copied for archiving purposes. This is a disadvantage of the centralized approach. In addition, some types of applications have been developed to create their own public/private key pairs and do not allow other keys to be imported and used. This means the keys would have to be created locally by these applications, and keys from a central server could not be used. These are just some of the considerations that need to be evaluated before any decision is made and implementation begins.

Hardware Security Modules PKIs can be constructed in software without special cryptographic hardware, and this is perfectly suitable for many environments. But software can be vulnerable to viruses, hackers, and hacking. If a company requires a higher level of protection than a purely software-based solution can provide, several hardware-based solutions are available. A hardware security module (HSM) is a physical device that safeguards cryptographic keys. HSMs enable a higher level of security for the use of keys, including generation and authentication. In most situations, HSM solutions are used only for the most critical and

sensitive keys, which are the root key and possibly the intermediate CA private keys. If those keys are compromised, the whole security of the PKI is gravely threatened. If a person obtained a root CA private key, she could digitally sign any certificate, and that certificate would be quickly accepted by all entities within the environment. Such an attacker might be able to create a certificate that has extremely high privileges, perhaps allowing her

to modify bank account information in a financial institution, and no alerts or warnings would be initiated because the ultimate CA, the root CA, signed it.

Tech Tip

Storing Critical Keys HSMs take many different forms, including embedded cards, network-attached devices, and even USB flash drives. HSMs assist in the use of cryptographic keys across the lifecycle. They can provide dedicated support for centralized lifecycle management, from generation to distribution, storage, termination, archiving, and recordkeeping. HSMs can increase the efficiency of cryptographic operations and assist in compliance efforts. Common uses include use in PCI DSS solutions, DNSSEC, signing operations including certificates, code, documents, and e-mail, and large-scale data encryption efforts.

Private Key Protection Although a PKI implementation can be complex, with many different components and options, a critical concept common to all PKIs must be understood and enforced: the private key needs to stay private. A digital signature is created solely for the purpose of proving who sent a particular message by using a private key. This rests on the assumption that only one person has access to this private key. If an imposter obtains a user’s private key, authenticity and nonrepudiation can no longer be claimed or proven. When a private key is generated for the first time, it must be stored

somewhere for future use. This storage area is referred to as a key store, and it is usually created by the application registering for a certificate, such as a web browser, smart card software, or other application. In most implementations, the application will prompt the user for a password, which will be used to create an encryption key that protects the key store. So, for example, if Cheryl used her web browser to register for a certificate, her private key would be generated and stored in the key store. Cheryl would then be prompted for a password, which the software would

use to create a key that will encrypt the key store. When Cheryl needs to access this private key later that day, she will be prompted for the same password, which will decrypt the key store and allow her access to her private key. Unfortunately, many applications do not require that a strong password

be created to protect the key store, and in some implementations the user can choose not to provide a password at all. The user still has a private key available, and it is bound to the user’s identity, so why is a password even necessary? If, for example, Cheryl decided not to use a password, and another person sat down at her computer, he could use her web browser and her private key and digitally sign a message that contains a nasty virus. If Cheryl’s coworker Cliff received this message, he would think it came from Cheryl, open the message, and download the virus. The moral to this story is that users should be required to provide some type of authentication information (password, smart card, PIN, or the like) before being able to use private keys. Otherwise, the keys could be used by other individuals or imposters, and authentication and nonrepudiation would be of no use. Because a private key is a crucial component of any PKI

implementation, the key itself should contain the necessary characteristics and be protected at each stage of its life. The following list sums up the characteristics and requirements of proper private key use:

The security associated with the use of public key cryptography revolves around the security of the private key. Nonrepudiation depends upon the principle that the private key is only accessible to the holder of the key. If another person has access to the private key, they can impersonate the proper key holder.

The key size should provide the necessary level of protection for the environment.

The lifetime of the key should correspond with how often it is used

and the sensitivity of the data it is protecting.

The key should be changed at the end of its lifetime and not used past its allowed lifetime.

Where appropriate, the key should be properly destroyed at the end of its lifetime.

The key should never be exposed in clear text.

No copies of the private key should be made if it is being used for digital signatures.

The key should not be shared.

The key should be stored securely.

Authentication should be required before the key can be used.

The key should be transported securely.

Software implementations that store and use the key should be evaluated to ensure they provide the necessary level of protection.

If digital signatures will be used for legal purposes, these points and others may need to be audited to ensure that true authenticity and nonrepudiation are provided.

The most sensitive and critical public/private key pairs are those used by CAs to digitally sign certificates. These need to be highly protected because if they were ever compromised, the trust relationship between the CA and all of the end-entities would be threatened. In high-security environments, these keys are often kept in a tamper-proof hardware encryption store, such as an HSM, and are accessible only to individuals with a need to know.

Key Recovery

One individual could have one, two, or many key pairs that are tied to his or her identity. That is because users may have different needs and requirements for public/private key pairs. As mentioned earlier, certificates can have specific attributes and usage requirements dictating how their corresponding keys can and cannot be used. For example, David can have one key pair he uses to encrypt and transmit symmetric keys, another key pair that allows him to encrypt data, and yet another key pair to perform digital signatures. David can also have a digital signature key pair for his work-related activities and another key pair for personal activities, such as e-mailing his friends. These key pairs need to be used only for their intended purposes, and this is enforced through certificate attributes and usage values. If a company is going to perform key recovery and maintain a key

recovery system, it will generally back up only the key pair used to encrypt data, not the key pairs that are used to generate digital signatures. The reason that a company archives keys is to ensure that if a person leaves the company, falls off a cliff, or for some reason is unavailable to decrypt important company information, the company can still get to its company- owned data. This is just a matter of the organization protecting itself. A company would not need to be able to recover a key pair that is used for digital signatures, since those keys are to be used only to prove the authenticity of the individual who sent a message. A company would not benefit from having access to those keys and really should not have access to them, since they are tied to one individual for a specific purpose. Two systems are important for backing up and restoring cryptographic

keys: key archiving and key recovery. Key archiving is a way of backing up keys and securely storing them in a repository; key recovery is the process of restoring lost keys to the users or the company.

Exam Tip: Key archiving is the process of storing a set of keys to be used as a backup should something happen to the original set. Key recovery is the process of using the backup keys.

If keys are backed up and stored in a centralized computer, this system must be tightly controlled, because if it were compromised, an attacker would have access to all keys for the entire infrastructure. Also, it is usually unwise to authorize a single person to be able to recover all the keys within the environment, because that person could use this power for evil purposes instead of just recovering keys when they are needed for legitimate purposes. In security systems, it is best not to fully trust anyone. Dual control can be used as part of a system to back up and archive data

encryption keys. PKI systems can be configured to require multiple individuals to be involved in any key recovery process. When a key recovery is required, at least two people can be required to authenticate by the key recovery software before the recovery procedure is performed. This enforces separation of duties, which means that one person cannot complete a critical task by himself. Requiring two individuals to recover a lost key together is called dual control, which simply means that two people have to be present to carry out a specific task.

Tech Tip

Keysplitting Secret splitting using m of n authentication schemes can improve security by requiring that multiple people perform critical functions, preventing a single party from compromising a secret. Be sure to understand the concept of m of n for the CompTIA Security+ exam.

This approach to key recovery is referred to as the m of n authentication, where n number of people can be involved in the key recovery process, but at least m (which is a smaller number than n) must be involved before the task can be completed. The goal is to minimize fraudulent or improper use of access and permissions. A company would not require all possible individuals to be involved in the recovery process, because getting all the people together at the same time could be impossible considering meetings, vacations, sick time, and travel. At least some of all possible

individuals must be available to participate, and this is the subset m of the number n. This form of secret splitting can increase security by requiring multiple people to perform a specific function. Requiring too many people for the m subset increases issues associated with availability, whereas requiring too few increases the risk of a small number of people colluding to compromise a secret.

Exam Tip: Recovery agent is the term for an entity that is given a public key certificate for recovering user data that is encrypted. This is the most common type of recovery policy used in PKI but adds the risk of the recovery agent having access to secured information.

All key recovery procedures should be highly audited. The audit logs should capture at least what keys were recovered, who was involved in the process, and the time and date. Keys are an integral piece of any encryption cryptosystem and are critical to a PKI environment, so you need to track who does what with them.

Key Escrow Key recovery and key escrow are terms that are often used interchangeably, but they actually describe two different things. You should not use them interchangeably after you have read this section.

Exam Tip: Key recovery is a process that allows for lost keys to be recovered. Key escrow is a process of giving keys to a third party so that they can decrypt and read sensitive information when this need arises.

Key escrow is the process of giving keys to a third party so that they can decrypt and read sensitive information if the need arises. Key escrow

almost always pertains to handing over encryption keys to the government, or to another higher authority, so that the keys can be used to collect evidence during investigations. A key pair used in a person’s place of work may be required to be escrowed by the employer for two reasons. First, the keys are property of the enterprise, issued to the worker for use. Second, the firm may have need for them after an employee leaves the firm.

Exam Tip: Key escrow, allowing another trusted party to hold a copy of a key, has long been a controversial topic. This essential business process provides continuity should the authorized key- holding party leave an organization without disclosing keys. The security of the escrowed key is a concern, and it needs to be managed at the same security level as for the original key.

Several movements, supported by parts of the U.S. government, would require all or many people residing in the United States to hand over copies of the keys they use to encrypt communication channels. The movement in the late 1990s behind the Clipper chip is the most well- known effort to implement this requirement and procedure. It was suggested that all American-made communication devices should have a hardware encryption chip within them. The chip could be used to encrypt data going back and forth between two individuals, but if a government agency decided that it should be able to eavesdrop on this dialog, it would just need to obtain a court order. If the court order was approved, a law enforcement agent would take the order to two escrow agencies, each of which would have a piece of the key that was necessary to decrypt this communication information. The agent would obtain both pieces of the key and combine them, which would allow the agent to listen in on the encrypted communication outlined in the court order. The Clipper chip standard never saw the light of day because it seemed

too “Big Brother” to many American citizens. But the idea was that the encryption keys would be escrowed to two agencies, meaning that each agency would hold one piece of the key. One agency could not hold the

whole key, because it could then use this key to wiretap people’s conversations illegally. Splitting up the key is an example of separation of duties, put into place to try and prevent fraudulent activities. The current issue of governments demanding access to keys to decrypt information is covered in Chapter 24.

Public Certificate Authorities An individual or company may decide to rely on a CA that is already established and being used by many other individuals and companies—a public CA. A company, on the other hand, may decide that it needs its own CA for internal use, which gives the company more control over the certificate registration and generation process and allows it to configure items specifically for its own needs. This second type of CA is referred to as a private CA (or in-house CA), discussed in the next section. A public CA specializes in verifying individual identities and creating

and maintaining their certificates. These companies issue certificates that are not bound to specific companies or intracompany departments. Instead, their services are to be used by a larger and more diversified group of people and organizations. If a company uses a public CA, the company will pay the CA organization for individual certificates and for the service of maintaining these certificates. Some examples of public CAs are VeriSign (including GeoTrust and Thawte), Entrust, and GoDaddy.

Users can remove CAs from their browser list if they want to have more control over who their system trusts and who it doesn’t. Unfortunately, system updates can restore them, requiring regular certificate store maintenance.

One advantage of using a public CA is that it is usually well known and easily accessible to many people. Most web browsers have a list of public CAs installed and configured by default, along with their corresponding

root certificates. This means that if you install a web browser on your computer, it is already configured to trust certain CAs, even though you might have never heard of them before. So, if you receive a certificate from Bob, and his certificate was digitally signed by a CA listed in your browser, you automatically trust the CA and can easily walk through the process of verifying Bob’s certificate. This has raised some eyebrows among security professionals, however, since trust is installed by default, but the industry has deemed this is a necessary approach that provides users with transparency and increased functionality. Earlier in the chapter, the different certificate classes and their uses were

explained. No global standard defines these classes, the exact requirements for obtaining these different certificates, or their uses. Standards are in place, usually for a particular country or industry, but this means that public CAs can define their own certificate classifications. This is not necessarily a good thing for companies that depend on public CAs, because it does not provide to the company enough control over how it should interpret certificate classifications and how they should be used. This means another component needs to be carefully developed for

companies that use and depend on public CAs, and this component is referred to as the certificate policy (CP). This policy allows the company to decide what certification classes are acceptable and how they will be used within the organization. This is different from the CPS, which explains how the CA verifies entities, generates certificates, and maintains these certificates. The CP is generated and owned by an individual company that uses an external CA, and it allows the company to enforce its security decisions and control how certificates are used with its applications.

In-House Certificate Authorities An in-house CA is implemented, maintained, and controlled by the company that implemented it. This type of CA can be used to create certificates for internal employees, devices, applications, partners, and

customers. This approach gives the company complete control over how individuals are identified, what certification classifications are created, who can and cannot have access to the CA, and how the certifications can be used.

Tech Tip

Why In-House CAs? In-house CAs provide more flexibility for companies, which often integrate them into current infrastructures and into applications for authentication, encryption, and nonrepudiation purposes. If the CA is going to be used over an extended period of time, this can be a cheaper method of generating and using certificates than having to purchase them through a public CA. Setting up in-house certificate servers is relatively easy and can be done with simple software that targets both Windows and Linux servers.

Choosing Between a Public CA and an In-House CA When deciding between an in-house and public CA, various factors need to be identified and accounted for. Many companies have embarked upon implementing an in-house PKI environment with a rough estimate that would be implemented within x number of months and would cost approximately y amount in dollars. Without doing the proper homework, companies might not understand the current environment, might not completely hammer out the intended purpose of the PKI, and might not have enough skilled staff supporting the project; time estimates can double or triple and the required funds and resources can become unacceptable. Several companies have started on a PKI implementation, only to quit halfway through, resulting in wasted time and money, with nothing to show for it except heaps of frustration and many ulcers. In some situations, it is better for a company to use a public CA, since

public CAs already have the necessary equipment, skills, and technologies.

In other situations, companies may decide it is a better business decision to take on these efforts themselves. This is not always a strictly monetary decision—a specific level of security might be required. Some companies do not believe that they can trust an outside authority to generate and maintain their users’ and company’s certificates. In this situation, the scale may tip toward an in-house CA.

Certificate authorities come in many types: public, in-house, and outsourced. All of them perform the same functions, with the only difference being an organizational one. This can have a bearing on trust relationships, as one is more likely to trust in-house CAs over others for which there is arguably less control.

Each company is unique, with various goals, security requirements, functionality needs, budgetary restraints, and ideologies. The decision of whether to use a private CA or an in-house CA depends on the expansiveness of the PKI within the organization, how integrated it will be with different business needs and goals, its interoperability with a company’s current technologies, the number of individuals who will be participating, and how it will work with outside entities. This could be quite a large undertaking that ties up staff, resources, and funds, so a lot of strategic planning is required, and what will and won’t be gained from a PKI should be fully understood before the first dollar is spent on the implementation.

Outsourced Certificate Authorities The last available option for using PKI components within a company is to outsource different parts of it to a specific service provider. Usually, the more complex parts are outsourced, such as the CA, RA, CRL, and key recovery mechanisms. This occurs if a company does not have the necessary skills to implement and carry out a full PKI environment.

Tech Tip

Outsourced CA vs. Public CA An outsourced CA is different from a public CA in that it provides dedicated services, and possibly equipment, to an individual company. A public CA, in contrast, can be used by hundreds or thousands of companies—the CA doesn’t maintain specific servers and infrastructures for individual companies.

Although outsourced services might be easier for your company to implement, you need to review several factors before making this type of commitment. You need to determine what level of trust the company is willing to give to the service provider and what level of risk it is willing to accept. Often a PKI and its components serve as large security components within a company’s enterprise, and allowing a third party to maintain the PKI can introduce too many risks and liabilities that your company is not willing to undertake. The liabilities the service provider is willing to accept, the security precautions and procedures the outsourced CAs provide, and the surrounding legal issues need to be examined before this type of agreement is made. Some large vertical markets have their own outsourced PKI

environments set up because they share similar needs and usually have the same requirements for certification types and uses. This allows several companies within the same market to split the costs of the necessary equipment, and it allows for industry-specific standards to be drawn up and followed. For example, although many medical facilities work differently and have different environments, they have a lot of the same functionality and security needs. If several of them came together, purchased the necessary equipment to provide CA, RA, and CRL functionality, employed one person to maintain it, and then each connected its different sites to the centralized components, the medical facilities could save a lot of money and resources. In this case, not every facility would need to strategically plan its own full PKI, and each would not need

to purchase redundant equipment or employ redundant staff members. Figure 6.10 illustrates how one outsourced service provider can offer different PKI components and services to different companies, and how companies within one vertical market can share the same resources.

• Figure 6.10 A PKI service provider (represented by the four boxes) can offer different PKI components to companies.

A set of standards can be drawn up about how each different facility should integrate its own infrastructure and how it should integrate with the centralized PKI components. This also allows for less-complicated intercommunication to take place between the different medical facilities, which will ease information-sharing attempts.

Tying Different PKIs Together In some cases, more than one CA may be needed for a specific PKI to work properly, and several requirements must be met for different PKIs to intercommunicate. Here are some examples:

A company wants to be able to communicate seamlessly with its suppliers, customers, or business partners via a PKI.

One department within a company has higher security requirements than all other departments and thus needs to configure and control its own CA.

One department needs to have specially constructed certificates with unique fields and usages.

Different parts of an organization want to control their own pieces of the network and the CA that is encompassed within it.

The number of certificates that need to be generated and maintained would overwhelm one CA, so multiple CAs must be deployed.

The political culture of a company inhibits one department from being able to control elements of another department.

Enterprises are partitioned geographically, and different sites need their own local CA.

These situations can add much more complexity to the overall infrastructure, intercommunication capabilities, and procedures for certificate generation and validation. To control this complexity properly from the beginning, these requirements need to be understood, addressed, and planned for. Then the necessary trust model needs to be chosen and molded for the company to build upon. Selecting the right trust model will give the company a solid foundation from the beginning, instead of trying to add structure to an inaccurate and inadequate plan later on.

Trust Models Potential scenarios exist other than just having more than one CA—each of the companies or each department of an enterprise can actually represent a trust domain itself. A trust domain is a construct of systems, personnel, applications, protocols, technologies, and policies that work together to provide a certain level of protection. All of these components can work together seamlessly within the same trust domain because they are known to the other components within the domain and are trusted to some degree. Different trust domains are usually managed by different groups of administrators, have different security policies, and restrict outsiders from privileged access.

Tech Tip

Trust Models There are several forms of trust models associated with certificates. Hierarchical, peer-to- peer, and hybrid are the primary forms, with the web of trust being a form of hybrid. Each of these models has a useful place in the PKI architecture under different circumstances.

Most trust domains (whether individual companies or departments) usually are not islands cut off from the world—they need to communicate with other, less-trusted domains. The trick is to figure out how much two

different domains should trust each other, and how to implement and configure an infrastructure that would allow these two domains to communicate in a way that will not allow security compromises or breaches. This can be more difficult than it sounds. In the nondigital world, it is difficult to figure out who to trust, how to

carry out legitimate business functions, and how to ensure that one is not being taken advantage of or lied to. Jump into the digital world and add protocols, services, encryption, CAs, RAs, CRLs, and differing technologies and applications, and the business risks can become overwhelming and confusing. So start with a basic question: What criteria will we use to determine who we trust and to what degree? One example of trust considered earlier in the chapter is the driver’s

license issued by the DMV. Suppose, for example, that Bob is buying a lamp from Carol and he wants to pay by check. Since Carol does not know Bob, she does not know if she can trust him or have much faith in his check. But if Bob shows Carol his driver’s license, she can compare the name to what appears on the check, and she can choose to accept it. The trust anchor (the agreed-upon trusted third party) in this scenario is the DMV, since both Carol and Bob trust it more than they trust each other. Bob had to provide documentation to the DMV to prove his identity, that organization trusted him enough to generate a license, and Carol trusts the DMV, so she decides to trust Bob’s check. Consider another example of a trust anchor. If Joe and Stacy need to

communicate through e-mail and would like to use encryption and digital signatures, they will not trust each other’s certificate alone. But when each receives the other’s certificate and sees that it has been digitally signed by an entity they both do trust—the CA—they have a deeper level of trust in each other. The trust anchor here is the CA. This is easy enough, but when we need to establish trust anchors between different CAs and PKI environments, it gets a little more complicated. If two companies need to communicate using their individual PKIs, or if

two departments within the same company use different CAs, two separate trust domains are involved. The users and devices from these different

trust domains need to communicate with each other, and they need to exchange certificates and public keys, which means that trust anchors need to be identified and a communication channel must be constructed and maintained. A trust relationship must be established between two issuing authorities

(CAs). This happens when one or both of the CAs issue a certificate for the other CA’s public key, as shown in Figure 6.11. This means that each CA registers for a certificate and public key from the other CA. Each CA validates the other CA’s identification information and generates a certificate containing a public key for that CA to use. This establishes a trust path between the two entities that can then be used when users need to verify other users’ certificates that fall within the different trust domains. The trust path can be unidirectional or bidirectional, so either the two CAs trust each other (bidirectional) or only one trusts the other (unidirectional).

• Figure 6.11 A trust relationship can be built between two trust domains to set up a communication channel.

Exam Tip: Three forms of trust models are commonly found in PKIs:

• Hierarchical • Peer-to-peer • Hybrid

As illustrated in Figure 6.11, all the users and devices in trust domain 1 trust their own CA, CA 1, which is their trust anchor. All users and devices in trust domain 2 have their own trust anchor, CA 2. The two CAs have exchanged certificates and trust each other, but they do not have a common trust anchor between them. The trust models describe and outline the trust relationships between the

different CAs and different environments, which will indicate where the trust paths reside. The trust models and paths need to be thought out before implementation to restrict and control access properly and to ensure that as few trust paths as possible are used. Several different trust models can be used: the hierarchical, peer-to-peer, and hybrid models are discussed in the following sections.

Hierarchical Trust Model The hierarchical trust model is a basic hierarchical structure that contains a root CA, intermediate CAs, leaf CAs, and end-entities. The configuration is that of an inverted tree, as shown in Figure 6.12. The root CA is the ultimate trust anchor for all other entities in this infrastructure, and it generates certificates for the intermediate CAs, which in turn generate certificates for the leaf CAs, and the leaf CAs generate certificates for the end-entities (users, network devices, and applications).

• Figure 6.12 The hierarchical trust model outlines trust paths.

Intermediate CAs function to transfer trust between different CAs. These CAs are referred to as subordinate CAs because they are subordinate to the CA that they reference. The path of trust is walked up from the subordinate CA to the higher-level CA; in essence the subordinate CA is using the higher-level CA as a reference. As shown in Figure 6.12, no bidirectional trusts exist—they are all

unidirectional trusts, as indicated by the one-way arrows. Since no other

entity can certify and generate certificates for the root CA, it creates a self- signed certificate. This means that the certificate’s Issuer and Subject fields hold the same information, both representing the root CA, and the root CA’s public key will be used to verify this certificate when that time comes. This root CA certificate and public key are distributed to all entities within this trust model.

Tech Tip

Root CA If the root CA’s private key were ever compromised, all entities within the hierarchical trust model would be drastically affected, because this is their sole trust anchor. The root CA usually has a small amount of interaction with the intermediate CAs and end-entities, and can therefore be taken offline much of the time. This provides a greater degree of protection for the root CA, because when it is offline it is basically inaccessible.

Walking the Certificate Path When a user in one trust domain needs to communicate with a user in another trust domain, one user will need to validate the other’s certificate. This sounds simple enough, but what it really means is that each certificate for each CA, all the way up to a shared trusted anchor, also must be validated. If Debbie needs to validate Sam’s certificate, as shown in Figure 6.12, she actually also needs to validate the Leaf D CA and Intermediate B CA certificates, as well as Sam’s. So in Figure 6.12, we have a user, Sam, who digitally signs a message

and sends it and his certificate to Debbie. Debbie needs to validate this certificate before she can trust Sam’s digital signature. Included in Sam’s certificate is an Issuer field, which indicates that the certificate was issued by Leaf D CA. Debbie has to obtain Leaf D CA’s digital certificate and public key to validate Sam’s certificate. Remember that Debbie validates the certificate by verifying its digital signature. The digital signature was created by the certificate issuer using its private key, so Debbie needs to

verify the signature using the issuer’s public key. Debbie tracks down Leaf D CA’s certificate and public key, but she

now needs to verify this CA’s certificate, so she looks at the Issuer field, which indicates that Leaf D CA’s certificate was issued by Intermediate B CA. Debbie now needs to get Intermediate B CA’s certificate and public key. Debbie’s client software tracks this down and sees that the issuer for

Intermediate B CA is the root CA, for which she already has a certificate and public key. So Debbie’s client software had to follow the certificate path, meaning it had to continue to track down and collect certificates until it came upon a self-signed certificate. A self-signed certificate indicates that it was signed by a root CA, and Debbie’s software has been configured to trust this entity as her trust anchor, so she can stop there. Figure 6.13 illustrates the steps Debbie’s software had to carry out just to be able to verify Sam’s certificate.

• Figure 6.13 Verifying each certificate in a certificate path

This type of simplistic trust model works well within an enterprise that easily follows a hierarchical organizational chart, but many companies cannot use this type of trust model because different departments or offices require their own trust anchors. These demands can be derived from direct business needs or from interorganizational politics. This hierarchical model might not be possible when two or more companies need to communicate with each other. Neither company will let the other’s CA be the root CA, because each does not necessarily trust the other entity to that degree. In these situations, the CAs will need to work in a peer-to-peer relationship instead of in a hierarchical relationship.

Peer-to-Peer Model

In a peer-to-peer trust model, one CA is not subordinate to another CA, and no established trusted anchor between the CAs is involved. The end- entities will look to their issuing CA as their trusted anchor, but the different CAs will not have a common anchor. Figure 6.14 illustrates this type of trust model. The two different CAs

will certify the public key for each other, which creates a bidirectional trust. This is referred to as cross-certification, since the CAs are not receiving their certificates and public keys from a superior CA, but instead are creating them for each other.

• Figure 6.14 Cross-certification creates a peer-to-peer PKI model.

One of the main drawbacks to this model is scalability. Each CA must certify every other CA that is participating, and a bidirectional trust path must be implemented, as shown in Figure 6.15. If one root CA were certifying all the intermediate CAs, scalability would not be as much of an issue.

• Figure 6.15 Scalability is a drawback in cross-certification models.

Figure 6.15 represents a fully connected mesh architecture, meaning that each CA is directly connected to and has a bidirectional trust relationship with every other CA. As you can see in this illustration, the complexity of this setup can become overwhelming.

In any network model, fully connected mesh architectures are wasteful and expensive. In trust transfer models, the extra level of redundancy is just that: redundant and unnecessary.

Hybrid Trust Model

A company can be internally complex, and when the need arises to communicate properly with outside partners, suppliers, and customers in an authorized and secured manner, this complexity can make sticking to either the hierarchical or peer-to-peer trust model difficult, if not impossible. In many implementations, the different model types have to be combined to provide the necessary communication lines and levels of trust. In a hybrid trust model, the two companies have their own internal hierarchical models and are connected through a peer-to-peer model using cross-certification. Another option in this hybrid configuration is to implement a bridge CA.

Figure 6.16 illustrates the role that a bridge CA could play—it is responsible for issuing cross-certificates for all connected CAs and trust domains. The bridge is not considered a root or trust anchor, but merely the entity that generates and maintains the cross-certification for the connected environments.

• Figure 6.16 A bridge CA can control the cross-certification procedures.

Exam Tip: Three trust models exist: hierarchical, peer-to-peer, and hybrid. Hierarchical trust is like an upside-down tree, peer-to-peer is a lateral series of references, and hybrid is a combination of hierarchical and peer-to-peer trust.

Certificate-Based Threats Although certificates bring much capability to security through practical management of trust, they also can present threats. Because much of the actual work is done behind the scenes, without direct user involvement, a false sense of security might ensue. End users might assume that if an HTTPS connection was made with a server, they are securely connected to the proper server. Spoofing, phishing, pharming, and a wide range of sophisticated attacks prey on this assumption. Today, industry has responded with a high-assurance certificate that is signed and recognized by browsers. Using this example, we can examine how an attacker might prey on a user’s trust in software getting things correct. If a hacker wishes to have something recognized as legitimate, he may

have to obtain a certificate that proves this point to the end-user machine. One avenue would be to forge a false certificate, but this is challenging because of the public key signing of certificates by CAs. To overcome this problem, the hacker needs to install a false, self-signed root certificate on the end-user PC. This false key can then be used to validate malicious software as coming from a trusted source. This attack preys on the fact that end users do not know the contents of their root certificate store, nor do they have a means to validate changes. In an enterprise environment, this attack can be thwarted by locking down the certificate store and validating changes against a white list. This option really is not very practical for end users outside of an enterprise.

Stolen Certificates Certificates act as a form of trusted ID and are typically handled without end-user intervention. To ensure the veracity of a certificate, a series of cryptographic controls is employed, including digital signatures to provide proof of authenticity. This statement aside, stolen certificates have been used in multiple cases of computer intrusions/system attacks. Specially crafted malware has been designed to steal both private keys and digital certificates from machines. One of the most infamous malware programs, the Zeus bot, has functionality to perform this task.

A stolen certificate and/or private key can be used to bypass many security measures. Concern over stolen SSL / TLS credentials led to the creation of high-assurance certificates, which are discussed in Chapter 17.

Stolen certificates have been implemented in a wide range of attacks. Malware designed to imitate antivirus software has been found dating back to 2009. The Stuxnet attack on the Iranian nuclear production facility used stolen certificates from third parties that were not involved in any way other than the unwitting contribution of a passkey in the form of a certificate. In less than a month after the Sony Pictures Entertainment attack became public in 2014, malware using Sony certificates appeared. Whether the certificates came from the break-in or one of the previous Sony hacks is unknown, but the result is the same.

Chapter 6 Review

Lab Book Exercise

The following lab exercise from the companion lab manual, Principles of Computer Security Lab Manual, Fourth Edition, provides practical application of material covered in this chapter:

Lab 8.5w Using IPsec in Windows

Chapter Summary After reading this chapter and completing the exercises, you should understand the following about public key infrastructures.

Implement the basics of public key infrastructures

PKI solutions include certificate authorities (CAs) and registration authorities (RAs).

PKIs form the central management functionality used to enable encryption technologies.

The steps a user performs to obtain a certificate for use are listed in the text and are important to memorize.

Describe the role of registration authorities

RAs verify identities to be used on certificates.

RAs pass identity information to CAs for use in binding to a certificate.

Use digital certificates

Certificates are handled via a certificate server and client software.

There are three classes of certificates and they have the following typical uses:

Class 1 Personal e-mail use Class 2 Software signing

Class 3 Setting up a CA Understand the lifecycle of certificates

Certificates are generated, registered, and historically verified by the originating CA.

There are two main mechanisms to manage the revocation of a certificate: CRL and OCSP.

Keys, and hence certificates, have a lifecycle; they are created, used for a defined period of time, and then destroyed.

Explain the relationship between trust and certificate verification

Trust is based on an understanding of the needs of the user and what the item being trusted offers.

Certificate verification provides assurance that the data in the certificate is valid, not whether it meets the needs of the user.

Describe the roles of certificate authorities and certificate repositories

CAs create certificates for identified entities and maintain records of their issuance and revocation.

CRLs provide a means of letting users know when certificates have been revoked before their end-of-life date.

Identify centralized and decentralized infrastructures

There are three different architectures of CAs:

Hierarchical

Peer-to-peer

Hybrid

Multiple CAs can be used together to create a web of trust.

Describe public and in-house certificate authorities

Public CAs exist as a service that allows entities to obtain certificates from a trusted third party.

In-house certificates provide certificates that allow a firm a means to use certificates within company borders.

Key Terms authority revocation list (ARL) (142) CA certificate (136) certificate (128) certificate authority (CA) (130) certificate path (158) certificate repository (143) certificate revocation list (CRL) (140) certificate server (131) certificate signing request (CSR) (138) certification practices statement (CPS) (131) cross-certification certificate (137) digital certificate (130) dual control (150) end-entity certificate (136) hardware security module (HSM) (147) hierarchical trust model (157) hybrid trust model (159) key archiving (150) key escrow (150) key recovery (150) local registration authority (LRA) (132) Online Certificate Status Protocol (OCSP) (142)

peer-to-peer trust model (158) policy certificate (137) public key infrastructure (PKI) (129) registration authority (RA) (131)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. The _______________ is the trusted authority for certifying individuals’ identities and creating an electronic document indicating that individuals are who they say they are.

2. A(n) _______________ is the actual request to a CA containing a public key and the requisite information needed to generate a certificate.

3. The _______________ is a method of determining whether a certificate has been revoked that does not require local machine storage of CRLs.

4. The _______________ is the actual service that issues certificates based on the data provided during the initial registration process.

5. A physical device that safeguards cryptographic keys is called a(n) _______________.

6. A(n) _______________ is a holding place for individuals’ certificates and public keys that are participating in a particular PKI environment.

7. A(n) _______________ is used when independent CAs establish peer-to-peer trust relationships.

8. A(n) _______________ is a structure that provides all of the necessary components for different types of users and entities to be

able to communicate securely and in a predictable manner.

9. _______________ is the process of giving keys to a third party so that they can decrypt and read sensitive information if the need arises.

10. In a(n) _______________, one CA is not subordinate to another CA, and there is no established trust anchor between the CAs involved.

Multiple-Choice Quiz 1. When a user wants to participate in a PKI, what component does he

or she need to obtain, and how does that happen?

A. The user submits a certificate request to the CA.

B. The user submits a key pair request to the CRL.

C. The user submits a certificate request to the RA.

D. The user submits proof of identification to the CA.

2. How does a user validate a digital certificate that is received from another user?

A. The user first sees whether her system has been configured to trust the CA that digitally signed the other user’s certificate and then validates that CA’s digital signature.

B. The user calculates a message digest and compares it to the one attached to the message.

C. The user first sees whether her system has been configured to trust the CA that digitally signed the certificate and then validates the public key that is embedded within the certificate.

D. The user validates the sender’s digital signature on the message.

3. What is the purpose of a digital certificate?

A. It binds a CA to a user’s identity.

B. It binds a CA’s identity to the correct RA.

C. It binds an individual identity to an RA.

D. It binds an individual identity to a public key.

4. What steps does a user’s software take to validate a CA’s digital signature on a digital certificate?

A. The user’s software creates a message digest for the digital certificate and decrypts the encrypted message digest included within the digital certificate. If the decryption performs properly and the message digest values are the same, the certificate is validated.

B. The user’s software creates a message digest for the digital signature and encrypts the message digest included within the digital certificate. If the encryption performs properly and the message digest values are the same, the certificate is validated.

C. The user’s software creates a message digest for the digital certificate and decrypts the encrypted message digest included within the digital certificate. If the user can encrypt the message digest properly with the CA’s private key and the message digest values are the same, the certificate is validated.

D. The user’s software creates a message digest for the digital signature and encrypts the message digest with its private key. If the decryption performs properly and the message digest values are the same, the certificate is validated.

5. Why would a company implement a key archiving and recovery system within the organization?

A. To make sure all data encryption keys are available for the company if and when it needs them

B. To make sure all digital signature keys are available for the company if and when it needs them

C. To create session keys for users to be able to access when they need to encrypt bulk data

D. To back up the RA’s private key for retrieval purposes

6. Within a PKI environment, where does the majority of the trust actually lie?

A. All users and devices within an environment trust the RA, which allows them to indirectly trust each other.

B. All users and devices within an environment trust the CA, which allows them to indirectly trust each other.

C. All users and devices within an environment trust the CRL, which allows them to indirectly trust each other.

D. All users and devices within an environment trust the CPS, which allows them to indirectly trust each other.

7. Which of the following properly describes what a public key infrastructure (PKI) actually is?

A. A protocol written to work with a large subset of algorithms, applications, and protocols

B. An algorithm that creates public/private key pairs

C. A framework that outlines specific technologies and algorithms that must be used

D. A framework that does not specify any technologies but provides a foundation for confidentiality, integrity, and availability services

8. Once an individual validates another individual’s certificate, what is the use of the public key that is extracted from this digital

certificate?

A. The public key is now available to use to create digital signatures.

B. The user can now encrypt session keys and messages with this public key and can validate the sender’s digital signatures.

C. The public key is now available to encrypt future digital certificates that need to be validated.

D. The user can now encrypt private keys that need to be transmitted securely.

9. Why would a digital certificate be added to a certificate revocation list (CRL)?

A. If the public key had become compromised in a public repository

B. If the private key had become compromised

C. If a new employee joined the company and received a new certificate

D. If the certificate expired

10. How can users have faith that the CRL was not modified to present incorrect information?

A. The CRL is digitally signed by the CA.

B. The CRL is encrypted by the CA.

C. The CRL is open for anyone to post certificate information to.

D. The CRL is accessible only to the CA.

Essay Quiz

1. Describe the pros and cons of establishing a key archiving system program for a small- to medium-sized business.

2. Why would a small- to medium-sized firm implement a PKI solution? What business benefits would ensue from such a course of action?

3. Describe the steps involved in verifying a certificate’s validity. 4. Describe the steps in obtaining a certificate. 5. Compare and contrast the hierarchical trust model, peer-to-peer trust

model, and hybrid trust model.

Lab Projects

• Lab Project 6.1 Investigate the process of obtaining a personal certificate or digital ID for e-mail usage. What information is needed, what are the costs, and what protection is afforded based on the vendor?

• Lab Project 6.2 Determine what certificates are registered with the browser instance on your computer.

chapter 7 PKI Standards and Protocols

The nice thing about standards is that you have so many to choose from.

—ANDREW S. TANENBAUM

N

In this chapter, you will learn how to

Identify the standards involved in establishing an interoperable Internet PKI

Explain interoperability issues with PKI standards

Describe how the common Internet protocols implement the PKI standards

one of the still steadily growing Internet commerce would be possible without the use of standards and protocols that provide a common, interoperable environment for exchanging information securely. Due

to the wide distribution of Internet users and businesses, the most practical solution to date has been the commercial implementation of public key infrastructures (PKIs). This chapter examines the standards and protocols involved in secure

Internet transactions and e-business using a PKI. Although you may use only a portion of the related standards and protocols on a daily basis, you should understand how they interact to provide the services that are critical for security: confidentiality, integrity, availability, authentication, and nonrepudiation. This chapter will also include some related standards, such as FIPS and the Common Criteria.

Chapter 6 introduced the algorithms and techniques used to implement a public PKI, but, as you probably noticed, there is a lot of room for interpretation. Various organizations have developed and implemented standards and protocols that have been accepted as the basis for secure interaction in a PKI environment. These standards fall into three general categories:

Tech Tip

Revolutionary Technologies The 1976 public disclosure of asymmetric key algorithms by Diffie, Hellman, Rivest, Shamir,

and Adleman changed secure communications in a world-shattering way. It was a technology that met the need of another emerging technology; the development of the Internet during this same time led to the need for secure communications between anonymous parties—combined, a technologically revolutionary event.

Standards that define the PKI These standards define the data and data structures exchanged and the means for managing that data to provide the functions of the PKI (certificate issuance, storage, revocation, registration, and management).

Standards that define the interface between applications and the underlying PKI These standards use the PKI to establish the services required by applications (S/MIME, SSL, and TLS).

Other standards These standards don’t fit neatly in either of the other two categories. They provide bits and pieces that glue everything together; they not only can address the PKI structure and the methods and protocols for using it, but can also provide an overarching business process environment for PKI implementation (for example, ISO/IEC 27002, Common Criteria, and the Federal Information Processing Standards Publications [FIPS PUBS]).

Figure 7.1 shows the relationships between these standards and protocols and conveys the interdependence of the standards and protocols discussed in this chapter. The Internet public key infrastructure (PKI) relies on three main standards for establishing interoperable PKI services: PKI X.509 (PKIX), Public Key Cryptography Standards (PKCS), and X.509. Other protocols and standards help define the management and operation of the PKI and related services—Internet Security Association and Key Management Protocol (ISAKMP) and XML Key Management Specification (XKMS) are both key management protocols, while Certificate Management Protocol (CMP) is used for managing certificates. Certificate Enrollment Protocol (CEP) is an alternative certificate issuance, distribution, and revocation mechanism. Finally, Pretty Good Privacy (PGP) provides an alternative method spanning the protocol and

application levels.

• Figure 7.1 Relationships between PKI standards and protocols

This chapter examines each standard from the bottom up, starting with building an infrastructure through protocols and applications, and finishing with some of the inherent weaknesses of and potential attacks on a PKI.

PKIX and PKCS Two main standards have evolved over time to implement PKIs on a practical level on the Internet. Both are based on the X.509 certificate standard (discussed shortly in the “X.509” section) and establish complementary standards for implementing PKIs. PKIX and PKCS intertwine to define the most commonly used set of standards. PKIX was produced by the Internet Engineering Task Force (IETF) and

defines standards for interactions and operations for four component types: the user (end-entity), certificate authority (CA), registration authority (RA), and the repository for certificates and certificate revocation lists (CRLs). PKCS defines many of the lower-level standards for message syntax, cryptographic algorithms, and the like. The PKCS set of standards is a product of RSA Security. The PKIX working group was formed in 1995 to develop the standards

necessary to support PKIs. At the time, the X.509 Public Key Certificate (PKC) format was proposed as the basis for a PKI. X.509 includes information regarding data formats and procedures used for CA-signed PKCs, but it doesn’t specify values or formats for many of the fields within the PKC. PKIX provides standards for extending and using X.509 v3 certificates and for managing them, enabling interoperability between PKIs following the standards. PKIX uses the model shown in Figure 7.2 for representing the

components and users of a PKI. The user, called an end-entity, is not part of the PKI, but end-entities are either users of the PKI certificates, the subject of a certificate (an entity identified by it), or both. The certificate authority (CA) is responsible for issuing, storing, and revoking certificates—both PKCs and Attribute Certificates (ACs). The RA is responsible for management activities designated by the CA. The RA can, in fact, be a component of the CA rather than a separate component. The final component of the PKIX model is the repository, a system or group of distributed systems that provides certificates and CRLs to the end-entities. The certificate revocation list (CRL) is a digitally signed object that lists

all of the current but revoked certificates issued by a CA.

• Figure 7.2 The PKIX model

Tech Tip

PKI Essentials A PKI brings together policies, procedures, hardware, software, and end users to create, manage, store, distribute, and revoke digital certificates.

PKIX Standards Now that we have looked at how PKIX is organized, let’s take a look at

what PKIX does. Using X.509 v3, the PKIX working group addresses five major areas:

PKIX outlines certificate extensions and content not covered by X.509 v3 and the format of version 2 CRLs, thus providing compatibility standards for sharing certificates and CRLs between CAs and end- entities in different PKIs. The PKIX profile of the X.509 v3 PKC describes the contents, required extensions, optional extensions, and extensions that need not be implemented. The PKIX profile suggests a range of values for many extensions. In addition, PKIX provides a profile for version 2 CRLs, allowing different PKIs to share revocation information.

PKIX provides certificate management message formats and protocols, defining the data structures, management messages, and management functions for PKIs. The working group also addresses the assumptions and restrictions of their protocols. This standard identifies the protocols necessary to support online interactions between entities in the PKIX model. The management protocols support functions for entity registration, initialization of the certificate (possibly key-pair generation), issuance of the certificate, key-pair update, certificate revocation, cross-certification (between CAs), and key-pair recovery if available.

PKIX outlines certificate policies and certification practices statements (CPSs), establishing the relationship between policies and CPSs. A policy is a set of rules that helps determine the applicability of a certificate to an end-entity. For example, a certificate for handling routine information would probably have a policy on creation, storage, and management of key pairs quite different from a policy for certificates used in financial transactions, due to the sensitivity of the financial information. A CPS explains the practices used by a CA to issue certificates. In other words, the CPS is the method used to get the certificate, while the policy defines some characteristics of the certificate and how it will be handled and used.

PKIX specifies operational protocols, defining the protocols for certificate handling. In particular, protocol definitions are specified for using File Transfer Protocol (FTP) and Hypertext Transfer Protocol (HTTP) to retrieve certificates from repositories. These are the most common protocols for applications to use when retrieving certificates.

PKIX includes time-stamping and data certification and validation services, which are areas of interest to the PKIX working group, and which will probably grow in use over time. A time stamp authority (TSA) certifies that a particular entity existed at a particular time. A Data Validation and Certification Server (DVCS) certifies the validity of signed documents, PKCs, and the possession or existence of data. These capabilities support nonrepudiation requirements and are considered building blocks for a nonrepudiation service.

PKCs are the most commonly used certificates, but the PKIX working group has been working on two other types of certificates: Attribute Certificates and Qualified Certificates. An Attribute Certificate (AC) is used to grant permissions using rule-based, role-based, and rank-based access controls. ACs are used to implement a privilege management infrastructure (PMI). In a PMI, an entity (user, program, system, and so on) is typically identified as a client to a server using a PKC. There are then two possibilities: either the identified client pushes an AC to the server, or the server can query a trusted repository to retrieve the attributes of the client. This situation is modeled in Figure 7.3.

• Figure 7.3 The PKIX PMI model

The client push of the AC has the effect of improving performance, but no independent verification of the client’s permissions is initiated by the server. The alternative is to have the server pull the information from an AC issuer or a repository. This method is preferable from a security standpoint, because the server or server’s domain determines the client’s access rights. The pull method has the added benefit of requiring no changes to the client software. The Qualified Certificate (QC) is based on the term used within the

European Commission to identify certificates with specific legislative uses. This concept is generalized in the PKIX QC profile to indicate a certificate used to identify a specific individual (a single human rather than the entity of the PKC) with a high level of assurance in a nonrepudiation service. There are dozens of IETF Requests for Comment (RFCs) that have been

produced by the PKIX working group for each of these five areas.

For a complete list of current and pending documents associated with PKIX, see the Internet draft for the PKIX working group roadmap (https://www.ietf.org/archive/id/draft-ietf-pkix-roadmap-09.txt/).

PKCS RSA Laboratories created the Public Key Cryptography Standards (PKCS) to fill some of the gaps in the standards that existed in PKI implementation. As they have with the PKIX standards, PKI developers have adopted many of these standards as a basis for achieving interoperability between different CAs. PKCS is composed of a set of (currently) 13 active standards, with 2 other standards that are no longer active. The standards are referred to as PKCS #1 through PKCS #15, as listed in Table 7.1. The standards combine to establish a common base for services required in a PKI.

Table 7.1 PKCS Standards

Though adopted early in the development of PKIs, some of these standards are being phased out. For example, PKCS #6 is being replaced by X.509 v3 (covered shortly in the “X.509” section) and PKCS #7 and PKCS #10 are being used less, as their PKIX counterparts are being adopted.

Why You Need to Know the PKIX and PKCS Standards If your company is planning to use one of the existing certificate servers to support e-commerce, you may not need to know the specifics of these standards (except perhaps for the CompTIA Security+ exam). However, if you plan to implement a private PKI to support secure services within your organization, you need to understand what standards are out there and how the decision to use a particular PKI implementation (either homegrown or commercial) may lead to incompatibilities with other certificate-issuing entities. You must consider your business-to-business requirements when you’re deciding how to implement a PKI within your organization.

Exam Tip: All of the standards and protocols discussed in this chapter are the “vocabulary” of the computer security industry. You should be well versed in all these titles and their purposes and operations.

Tech Tip

X.509 Essentials X.509 specifies standard formats for public key certificates, certificate revocation lists, and Attribute Certificates.

X.509 What is a certificate? As explained in Chapter 6, a certificate is merely a data structure that binds a public key to subjects (unique names, DNS entries, or e-mails) and is used to authenticate that a public key indeed belongs to the subject. In the late 1980s, the X.500 OSI Directory Standard was defined by the International Organization for Standardization (ISO) and the International Telecommunication Union (ITU). It was developed for implementing a network directory system, and part of this directory standard was the concept of authentication of entities within the directory. X.509 is the portion of the X.500 standard that addresses the structure of certificates used for authentication. Several versions of the X.509 certificates have been created, with

version 3 being the current version (as this is being written). Each version has extended the contents of the certificates to include additional information necessary to use certificates in a PKI. The original ITU X.509 definition was published in 1988, was formerly referred to as CCITT X.509, and is sometimes referred to as ISO/IEC/ITU 9594-8. Version 3 added additional optional extensions for more subject identification information, key attribute information, policy information, and certification path constraints. In addition, version 3 allows additional extensions to be defined in standards or to be defined and registered by organizations or communities. Certificates are used to encapsulate the information needed to

authenticate an entity. The X.509 specification defines a hierarchical certification structure that relies on a root CA that is self-certifying (meaning it issues its own certificate). All other certificates can be traced back to such a root through a path. A CA issues a certificate to a uniquely identifiable entity (person, corporation, computer, and so on)—issuing a certificate to “John Smith” would cause some real problems if that were all the information the CA had when issuing the certificate. We are saved somewhat by the requirement that the CA determines what identifier is unique (the distinguished name), but when certificates and trust are

extended between CAs, the unique identification becomes critical.

Cross Check Certificates A detailed description of certificates and the supporting public key infrastructure is provided in Chapter 6.

SSL/TLS Secure Sockets Layer (SSL) and Transport Layer Security (TLS) provide the most common means of interacting with a PKI and certificates. The older, SSL protocol was introduced by Netscape as a means of providing secure connections for web transfers using encryption. These two protocols provide secure connections between the client and server for exchanging information. They also provide server authentication (and optionally, client authentication) and confidentiality of information transfers. See Chapter 17 for a detailed explanation.

Tech Tip

SSL/TLS Simplified SSL and TLS are cryptographic protocols to provide data integrity and security over networks by encrypting network connections at the transport layer. In many cases people use the term SSL even when TLS is in fact the protocol being used.

The IETF established the TLS working group in 1996 to develop a standard transport layer security protocol. The working group began with SSL version 3.0 as its basis and released RFC 2246, “The TLS Protocol Version 1.0,” in 1999 as a proposed standard. The working group also published RFC 2712, “Addition of Kerberos Cipher Suites to Transport

Layer Security (TLS),” as a proposed standard, and two RFCs on the use of TLS with HTTP. Like its predecessor, TLS is a protocol that ensures privacy between communicating applications and their users on the Internet. When a server and client communicate, TLS ensures that no third party can eavesdrop or tamper with any message.

SSL is deprecated. All versions of SSL, including v3, have exploitable vulnerabilities that make the protocol no longer considered secure. For all traffic where confidentiality is important, you should use TLS.

TLS is composed of two parts: the TLS Record Protocol and the TLS Handshake Protocol. The TLS Record Protocol provides connection security by using supported encryption methods. The TLS Record Protocol can also be used without encryption. The TLS Handshake Protocol allows the server and client to authenticate each other and to negotiate a session encryption algorithm and cryptographic keys before data is exchanged. Though TLS is based on SSL and is sometimes referred to as SSL, they

are not interoperable. However, the TLS protocol does contain a mechanism that allows a TLS implementation to back down to SSL 3.0. The difference between the two is the way they perform key expansion and message authentication computations. The TLS Record Protocol is a layered protocol. At each layer, messages may include fields for length, description, and content. The Record Protocol takes messages to be transmitted, fragments the data into manageable blocks, optionally compresses the data, applies a message authentication code (HMAC) to the data, encrypts it, and transmits the result. Received data is decrypted, verified, decompressed, and reassembled, and then delivered to higher- level clients. The TLS Handshake Protocol involves the following steps, which are

summarized in Figure 7.4:

• Figure 7.4 TLS Handshake Protocol

1. Exchange hello messages to agree on algorithms, exchange random values, and check for session resumption.

2. Exchange the necessary cryptographic parameters to allow the client and server to agree on a pre-master secret.

3. Exchange certificates and cryptographic information to allow the client and server to authenticate themselves.

4. Generate a master secret from the pre-master secret and exchange random values.

5. Provide security parameters to the record layer. 6. Allow the client and server to verify that their peer has calculated

the same security parameters and that the handshake occurred without tampering by an attacker.

Though it has been designed to minimize this risk, TLS still has potential vulnerabilities to a man-in-the-middle attack. A highly skilled and well-placed attacker can force TLS to operate at lower security levels. Regardless, through the use of validated and trusted certificates, a secure cipher suite can be selected for the exchange of data. Once established, a TLS session remains active as long as data is being

exchanged. If sufficient inactive time has elapsed for the secure connection to time out, it can be reinitiated.

Tech Tip

Disabling SSL Because all versions of SSL, including v3, have exploitable vulnerabilities that make the protocol no longer considered secure, users should not rely on it for security. Chrome no longer uses SSL. For Internet Explorer, you need to uncheck the SSL boxes under Internet Options.

Cipher Suites In many applications, the use of cryptography occurs as a collection of functions. Different algorithms can be used for authentication, encryption/decryption, digital signatures, and hashing. The term cipher suite refers to an arranged group of algorithms. For instance, TLS has a published TLS Cipher Suite Registry at www.iana.org/assignments/tls-

parameters/tls-parameters.xhtml. There is a wide range of ciphers, some old and some new, each with its

own strengths and weaknesses. Over time, new methods and computational abilities change the viability of ciphers. The concept of strong versus weak ciphers is an acknowledgment that, over time, ciphers can become vulnerable to attacks. The application or selection of ciphers should take into consideration that not all ciphers are still strong. When selecting a cipher for use, it is important to make an appropriate choice. For example, if a server offers SSL v3 and TLS, you should choose TLS only, as SSL v3 has been shown to be vulnerable.

ISAKMP The Internet Security Association and Key Management Protocol (ISAKMP) provides a method for implementing a key exchange protocol and for negotiating a security policy. It defines procedures and packet formats to negotiate, establish, modify, and delete security associates. Because it is a framework, it doesn’t define implementation-specific protocols, such as the key exchange protocol or hash functions. Examples of ISAKMP are the Internet Key Exchange (IKE) protocol and IPsec, which are used widely throughout the industry. An important definition for understanding ISAKMP is that of the term

security association. A security association (SA) is a relationship in which two or more entities define how they will communicate securely. ISAKMP is intended to support SAs at all layers of the network stack. For this reason, ISAKMP can be implemented on the transport layer using TCP or User Datagram Protocol (UDP), or it can be implemented on IP directly. Negotiation of an SA between servers occurs in two stages. First, the

entities agree on how to secure negotiation messages (the ISAKMP SA). Once the entities have secured their negotiation traffic, they then determine the SAs for the protocols used for the remainder of their communications. Figure 7.5 shows the structure of the ISAKMP header. This header is used during both parts of the ISAKMP negotiation.

• Figure 7.5 ISAKMP header format

The Initiator Cookie is set by the entity requesting the SA, and the responder sets the Responder Cookie. The Payload byte indicates the type of the first payload to be encapsulated. Payload types include security associations, proposals, key transforms, key exchanges, vendor identities, and other things. The Major and Minor Revision fields refer to the major version number and minor version number for the ISAKMP. The Exchange Type helps determine the order of messages and payloads. The Flags bits indicate options for the ISAKMP exchange, including whether the payload is encrypted, whether the initiator and responder have “committed” to the SA, and whether the packet is to be authenticated only (and is not encrypted). The final fields of the ISAKMP header indicate the Message Identifier and a Message Length. Payloads encapsulated within ISAKMP use a generic header, and each payload has its own header format. Once the ISAKMP SA is established, multiple protocol SAs can be

established using the single ISAKMP SA. This feature is valuable due to the overhead associated with the two-stage negotiation. SAs are valid for specific periods of time, and once the time expires, the SA must be renegotiated. Many resources are also available for specific implementations of ISAKMP within the IPsec protocol.

CMP The PKIX Certificate Management Protocol (CMP) is specified in RFC 4210. This protocol defines the messages and operations required to provide certificate management services within the PKIX model. Though part of the IETF PKIX effort, CMP provides a framework that works well with other standards, such as PKCS #7 and PKCS #10.

Tech Tip

CMP Summarized CMP is a protocol to obtain X.509 certificates in a PKI.

CMP provides for the following certificate operations: CA establishment, including creation of the initial CRL and export of the public key for the CA

Certification of an end-entity, including the following:

Initial registration and certification of the end-entity (registration, certificate issuance, and placement of the certificate in a repository)

Updates to the key pair for end-entities, required periodically and when a key pair is compromised or keys cannot be recovered

End-entity certificate updates, required when a certificate expires

Periodic CA key-pair updates, similar to end-entity key-pair

updates

Cross-certification requests, placed by other CAs

Certificate and CRL publication, performed under the appropriate conditions of certificate issuance and certificate revocation

Key-pair recovery, a service to restore key-pair information for an end-entity; for example, if a certificate password is lost or the certificate file is lost

Revocation requests, supporting requests by authorized entities to revoke a certificate

CMP also defines mechanisms for performing these operations, either online or offline using files, e-mail, tokens, or web operations.

XKMS The XML Key Management Specification defines services to manage PKI operations within the Extensible Markup Language (XML) environment. These services are provided for handling PKI keys and certificates automatically. Developed by the World Wide Web Consortium (W3C), XKMS is intended to simplify integration of PKIs and management of certificates in applications. As well as responding to problems of authentication and verification of electronic signatures, XKMS also allows certificates to be managed, registered, or revoked. XKMS services reside on a separate server that interacts with an

established PKI. The services are accessible via a simple XML protocol. Developers can rely on the XKMS services, making it less complex to interface with the PKI. The services provide for retrieving key information (owner, key value, key issuer, and the like) and key management (such as key registration and revocation). Retrieval operations rely on the XML signature for the necessary

information. Three tiers of service are based on the client requests and application requirements. Tier 0 provides a means of retrieving key

information by embedding references to the key within the XML signature. The signature contains an element called a retrieval method that indicates ways to resolve the key. In this case, the client sends a request, using the retrieval method, to obtain the desired key information. For example, if the verification key contains a long chain of X.509 v3 certificates, a retrieval method could be included to avoid sending the certificates with the document. The client would use the retrieval method to obtain the chain of certificates. For tier 0, the server indicated in the retrieval method responds directly to the request for the key, possibly bypassing the XKMS server. The tier 0 process is shown in Figure 7.6.

• Figure 7.6 XKMS tier 0 retrieval

With tier 1 operations, the client forwards the key-information portions of the XML signature to the XKMS server, relying on the server to perform the retrieval of the desired key information. The desired information can be local to the XKMS server, or it can reside on an external PKI system. The XKMS server provides no additional validation of the key information, such as checking whether the certificate has been revoked or is still valid. Just as in tier 0, the client performs final validation of the document. Tier 1 is called the locate service because it locates the appropriate key information for the client, as shown in Figure 7.7.

• Figure 7.7 XKMS tier 1 locate service

Tier 2 is called the validate service and is illustrated in Figure 7.8. In this case, just as in tier 1, the client relies on the XKMS service to retrieve the relevant key information from the external PKI. The XKMS server also performs data validation on a portion of the key information provided by the client for this purpose. This validation verifies the binding of the key information with the data indicated by the key information contained in the XML signature.

• Figure 7.8 XKMS tier 2 validate service

The primary difference between tier 1 and tier 2 is the level of involvement of the XKMS server. In tier 1, it can serve only as a relay or gateway between the client and the PKI. In tier 2, the XKMS server is actively involved in verifying the relation between the PKI information and the document containing the XML signature. XKMS relies on the client or underlying communications mechanism to

provide for the security of the communications with the XKMS server. The specification suggests using one of three methods for ensuring server authentication, response integrity, and relevance of the response to the request: digitally signed correspondence, a transport layer security protocol (such as SSL, TLS, or WTLS), or a packet layer security protocol (such as IPsec). Obviously, digitally signed correspondence introduces its own issues regarding validation of the signature, which is the purpose of XKMS. It is possible to define other tiers of service. Tiers 3 and 4, an assertion

service and an assertion status service, respectively, are mentioned in the defining XKMS specification, but they are not defined. The specification states they “could” be defined in other documents. XKMS also provides services for key registration, key revocation, and

key recovery. Authentication for these actions is based on a password or passphrase, which is provided when the keys are registered and when they must be recovered.

S/MIME The Secure/Multipurpose Internet Mail Extensions (S/MIME) message specification is an extension to the MIME standard that provides a way to send and receive signed and encrypted MIME data. RSA Security created the first version of the S/MIME standard, using the RSA encryption algorithm and the PKCS series of standards. The second version dates from 1998 but had a number of serious restrictions, including the restriction to 40-bit Data Encryption Standard (DES). The current version of the IETF standard is dated July 2004 and requires the use of Advanced

Encryption Standard (AES).

Cross Check E-mail Encryption Want to understand e-mail encryption? Flip ahead to Chapter 16 on e-mail and instant messaging for more details on e-mail encryption. Then answer these questions:

Why is it important to encrypt e-mail? What impacts can malicious code have on a business?

Why is instant messaging a higher risk than e-mail?

The changes in the S/MIME standard have been so frequent that the standard has become difficult to implement until v3. Far from having a stable standard for several years that product manufacturers could have time to gain experience with, there were many changes to the encryption algorithms being used. Just as importantly, and not immediately clear from the IETF documents, the standard places reliance upon more than one other standard for it to function. Key among these is the format of a public key certificate as expressed in the X.509 standard.

IETF S/MIME History The S/MIME v2 specifications outline a basic strategy for providing security services for e-mail but lack many security features required by the Department of Defense (DoD) for use by the military. Shortly after the decision was made to revise the S/MIME v2 specifications, the DoD, its vendor community, and commercial industry met to begin development of the enhanced specifications. These new specifications would be known as S/MIME v3. Participants agreed that backward compatibility between S/MIME v3 and v2 should be preserved; otherwise, S/MIME v3– compatible applications would not be able to work with older S/MIME v2–compatible applications.

A minimum set of cryptographic algorithms was mandated so that different implementations of the new S/MIME v3 set of specifications could be interoperable. This minimum set must be implemented in an application for it to be considered S/MIME-compliant. Applications can implement additional cryptographic algorithms to meet their customers’ needs, but the minimum set must also be present in the applications for interoperability with other S/MIME applications. Thus, users are not forced to use S/MIME-specified algorithms; they can choose their own, but if the application is to be considered S/MIME-compliant, the standard algorithms must also be present.

IETF S/MIME v3 Specifications Building upon the original work by the IMC-organized group, the IETF has worked hard to enhance the S/MIME v3 specifications. The ultimate goal is to have the S/MIME v3 specifications receive recognition as an Internet standard. The current IETF S/MIME v3 set of specifications includes the following:

Cryptographic Message Syntax (CMS)

S/MIME v3 message specification

S/MIME v3 certificate-handling specification

Enhanced security services (ESS) for S/MIME

Tech Tip

S/MIME in a Nutshell S/MIME provides two security services to e-mail: digital signatures and message encryption. Digital signatures verify sender identity, and encryption can keep contents private during transmission. These services can be used independently of each other, and provide the foundational basis for message security.

The CMS defines a standard syntax for transmitting cryptographic information about contents of a protected message. Originally based on the PKCS #7 version 1.5 specification, the CMS specification was enhanced by the IETF S/MIME working group to include optional security components. Just as the S/MIME v3 provides backward compatibility with v2, CMS provides backward compatibility with PKCS #7, so applications will be interoperable even if the new components are not implemented in a specific application. Integrity, authentication, and nonrepudiation security features are

provided by using digital signatures using the SignedData syntax described by the CMS. CMS also describes what is known as the EnvelopedData syntax to provide confidentiality of the message’s content through the use of encryption. The PKCS #7 specification supports key encryption algorithms, such as RSA. Algorithm independence is promoted through the addition of several fields to the EnvelopedData syntax in CMS, which is the major difference between the PKCS #7 and CMS specifications. The goal was to be able to support specific algorithms such as Diffie-Hellman and the Key Exchange Algorithm (KEA), which is implemented on the Fortezza Crypto Card developed for the DoD. One final significant change to the original specifications is the ability to include X.509 Attribute Certificates in the SignedData and EnvelopedData syntaxes for CMS.

CMS Triple-Encapsulated Message An interesting feature of CMS is the ability to nest security envelopes to provide a combination of security features. As an example, a CMS triple- encapsulated message can be created in which the original content and associated attributes are signed and encapsulated within the inner Signed- Data object. The inner SignedData object is in turn encrypted and encapsulated within an EnvelopedData object. The resulting EnvelopedData object is then also signed and finally encapsulated within a second SignedData object, the outer SignedData object. Usually the inner SignedData object is signed by the original user and the outer SignedData object is signed by another entity, such as a firewall or a mail list agent,

providing an additional level of security. This triple encapsulation is not required of every CMS object. All that is

required is a single SignedData object created by the user to sign a message or an EnvelopedData object if the user desired to encrypt a message.

OpenPGP is a widely used e-mail encryption standard. A nonproprietary protocol for encrypting e-mail using public key cryptography, it is based on PGP as originally developed by Phil Zimmermann, and is defined by the OpenPGP working group of the IETF proposed standard RFC 4880.

PGP Pretty Good Privacy (PGP) is a popular program that is used to encrypt and decrypt e-mail and files. It also provides the ability to digitally sign a message so the receiver can be certain of the sender’s identity. Taken together, encrypting and signing a message allows the receiver to be assured of who sent the message and to know that it was not modified during transmission. Public-domain versions of PGP have been available for years, as have inexpensive commercial versions. PGP was one of the most widely used programs and was frequently used

by both individuals and businesses to ensure data and e-mail privacy. It was developed by Philip R. Zimmermann in 1991 and quickly became a de facto standard for e-mail security. The popularity of PGP lead to the OpenPGP Internet standard, RFC 4880, and open source solutions. GNU Privacy Guard (GPG) is a common alternative to PGP in use today.

Tech Tip

A PGP Personal Note

After distributing PGP in 1991, including (indirectly) internationally, Zimmermann became a formal target of a criminal investigation by the U.S. government in 1993 for exporting munitions without a license, because cryptosystems using keys larger than 40 bits were considered “munitions” under U.S. export law. Zimmermann proceeded to publish the entire source code of PGP in a hardback book, which, unlike software, is protected from export laws by the First Amendment of the U.S. Constitution. The investigation of Zimmermann was dropped after several years.

How PGP Works PGP uses a variation of the standard public key encryption process. In public key encryption, an individual (here called the creator) uses the encryption program to create a pair of keys. One key is known as the public key and is designed to be given freely to others. The other key is called the private key and is designed to be known only by the creator. Individuals who want to send a private message to the creator encrypt the message using the creator’s public key. The algorithm is designed such that only the private key can decrypt the message, so only the creator will be able to decrypt it. This method, known as public key or asymmetric encryption, is time

consuming. Symmetric encryption uses only a single key and is generally faster. It is because of this that PGP is designed the way it is. PGP uses a symmetric encryption algorithm to encrypt the message to be sent. It then encrypts the symmetric key used to encrypt this message with the public key of the intended recipient. Both the encrypted key and message are then sent. The receiver’s version of PGP first decrypts the symmetric key with the private key supplied by the recipient and then uses the resulting decrypted key to decrypt the rest of the message. PGP can use two different public key algorithms: Rivest-Shamir-

Adleman (RSA) and Diffie-Hellman. The RSA version uses the International Data Encryption Algorithm (IDEA) and a short symmetric key to encrypt the message and then uses RSA to encrypt the short IDEA key using the recipient’s public key. The Diffie-Hellman version uses the Carlisle Adams and Stafford Tavares (CAST) algorithm to encrypt the

message and the Diffie-Hellman algorithm to encrypt the CAST key. To decrypt the message, the reverse is performed. The recipient uses their private key to decrypt the IDEA or CAST key, and then uses that decrypted key to decrypt the message. These are both illustrated in Figure 7.9.

• Figure 7.9 How PGP works for encryption

To generate a digital signature, PGP takes advantage of another property of public key encryption schemes. Normally, the sender encrypts using the receiver’s public key and the message is decrypted at the other end using the receiver’s private key. The process can be reversed so that the sender encrypts (signs) with his own private key. The receiver then decrypts the message with the sender’s public key. Since the sender is the only individual who has a key that will correctly be decrypted with the sender’s public key, the receiver knows that the message was created by the sender who claims to have sent it. The way PGP accomplishes this task is to generate a hash value from the user’s name and other signature information. This hash value is then encrypted with the sender’s private key known only by the sender. The receiver uses the sender’s public key, which is available to everyone, to decrypt the hash value. If the decrypted hash value matches the hash value sent as the digital signature for the message, then the receiver is assured that the message was sent by the sender who claims to have sent it. Typically, versions of PGP contain a user interface that works with

common e-mail programs such as Microsoft Outlook. If you want others to be able to send you an encrypted message, you need to register your public key, generated by your PGP program, with a PGP public key server. Alternatively, you have to either send your public key to all those who want to send you an encrypted message or post your key to some location from which they can download it, such as your web page. Note that using a public key server is the better method, for all the reasons of trust described in the discussion of PKIs in Chapter 6.

Tech Tip

Where Can You Use PGP?

For many years the U.S. government waged a fight over the exportation of PGP technology, and for many years its exportation was illegal. Today, however, PGP-encrypted e-mail can be exchanged with most users outside the United States, and many versions of PGP are available from numerous international sites. Of course, being able to exchange PGP-encrypted e-mail requires that the individuals on both sides of the communication have valid versions of PGP. Interestingly, international versions of PGP are just as secure as domestic versions—a feature that is not true of other encryption products. It should be noted that the freeware versions of PGP are not licensed for commercial purposes.

HTTPS Most web activity occurs using HTTP, but this protocol is prone to interception. HTTPS uses either SSL or TLS to secure the communication channel. Originally developed by Netscape Communications and implemented in its browser, HTTPS has since been incorporated into most common browsers. HTTPS uses the standard TCP port 443 for TCP/IP communications rather than the standard port 80 used for HTTP. As previously discussed, because of vulnerabilities in SSL, only TLS is recommended for HTTPS today.

IPsec IPsec is a collection of IP security features designed to introduce security at the network or packet-processing layer in network communication. Other approaches have attempted to incorporate security at higher levels of the TCP/IP suite such as at the level where applications reside. IPsec is designed to provide secure IP communications over the Internet. In essence, IPsec provides a secure version of the IP by introducing authentication and encryption to protect Layer 4 protocols. IPsec is optional for IPv4 but is required for IPv6. Obviously, both ends of the communication need to use IPsec for the encryption/decryption process to occur. IPsec provides two types of security service to ensure authentication and

confidentiality for either the data alone (referred to as IPsec transport mode) or for both the data and header (referred to as tunnel mode). See Chapter 11 for more detail on tunneling and IPsec operation. IPsec introduces several new protocols, including the Authentication Header (AH), which basically provides authentication of the sender, and the Encapsulating Security Payload (ESP), which adds encryption of the data to ensure confidentiality. IPsec also provides for payload compression before encryption using the IP Payload Compression Protocol (IPcomp). Frequently, encryption negatively impacts the ability of compression algorithms to fully compress data for transmission. By providing the ability to compress the data before encryption, IPsec addresses this issue.

CEP Certificate Enrollment Protocol (CEP) was originally developed by VeriSign for Cisco Systems. It was designed to support certificate issuance, distribution, and revocation using existing technologies. Its use has grown in client and CA applications. The operations supported include CA and RA public key distribution, certificate enrollment, certificate revocation, certificate query, and CRL query. One of the key goals of CEP was to use existing technology whenever

possible. It uses both PKCS #7 (Cryptographic Message Syntax Standard) and PKCS #10 (Certification Request Syntax Standard) to define a common message syntax. It supports access to certificates and CRLs using either the Lightweight Directory Access Protocol (LDAP) or the CEP- defined certificate query.

Other Standards There are many additional standards associated with information security that are not specifically or solely associated with PKI and/or cryptography. The remainder of the chapter will introduce these standards and protocols.

FIPS The Federal Information Processing Standards Publications (FIPS PUBS or simply FIPS) describe various standards for data communication issues. These documents are issued by the U.S. government through the National Institute of Standards and Technology (NIST), which is tasked with their development. NIST creates these publications when a compelling government need requires a standard for use in areas such as security or system interoperability and no recognized industry standard exists. Three categories of FIPS PUBS are currently maintained by NIST:

Hardware and software standards/guidelines

Data standards/guidelines

Computer security standards/guidelines

These documents require that products sold to the U.S. government comply with one (or more) of the FIPS standards. The standards can be obtained from www.nist.gov/itl/fips.cfm.

FIPS 140-2 relates to specific cryptographic standards for the validation of components used in U.S. government systems. Systems can be accredited to the FIPS 140-2 standard to demonstrate levels of security from “approved algorithms” to higher levels that include additional protections up to and including physical security and tamperproof mechanisms.

Common Criteria The Common Criteria for Information Technology Security (Common Criteria or CC) is the result of an effort to develop a joint set of security processes and standards that can be used by the international community. The major contributors to the CC are the governments of the United States, Canada, France, Germany, the Netherlands, and the United Kingdom. The

CC also provides a listing of laboratories that apply the criteria in testing security products. Products that are evaluated by one of the approved laboratories receive an Evaluation Assurance Level of EAL1 through EAL7 (EAL7 is the highest level), with EAL4, for example, designed for environments requiring a moderate to high level of independently assured security, and EAL1 being designed for environments in which some confidence in the correct operation of the system is required but where the threats to the system are not considered serious. The CC also provides a listing of products by function that have performed at a specific EAL.

WTLS The Wireless Transport Layer Security (WTLS) protocol is based on the TLS protocol. WTLS provides reliability and security for wireless communications using the Wireless Application Protocol (WAP). WTLS is necessary due to the limited memory and processing abilities of WAP- enabled phones. WTLS can be implemented in one of three classes: Class 1 is called

anonymous authentication but is not designed for practical use. Class 2 is called server authentication and is the most common model. The clients and server may authenticate using different means. Class 3 is server and client authentication. In Class 3 authentication, the client’s and server’s WTLS certificates are authenticated. Class 3 is the strongest form of authentication and encryption.

ISO/IEC 27002 (Formerly ISO 17799) ISO/IEC 27002 is a very popular and detailed standard for creating and implementing security policies. ISO/IEC 27002 was formerly ISO 17799, which was based on version 2 of the British Standard 7799 (BS7799) published in May 1999. With the increased emphasis placed on security in both the government and industry in recent years, many organizations are now training their audit personnel to evaluate their organizations against

the ISO/IEC 27002 standard. The standard is divided into 12 sections, each containing more detailed statements describing what is involved for that topic:

Risk assessment Determine the impact of risks Security policy Guidance and policy provided by management Organization of information security Governance structure to implement security policy

Asset management Inventory and classification of assets Human resources security Policies and procedures addressing security for employees including hires, changes, and departures

Physical and environmental security Protection of the computer facilities

Communications and operations management Management of technical security controls in systems and networks

Access control Restriction of access rights to networks, systems, applications, functions, and data

Information systems acquisition, development, and maintenance Building security into applications

Information security incident management Anticipating and responding appropriately to information security breaches

Business continuity management Protecting, maintaining, and recovering business-critical processes and systems

Compliance Ensuring conformance with information security policies, standards, laws, and regulations

SAML Security Assertion Markup Language (SAML) is a single sign-on

capability used for web applications to ensure user identities can be shared and are protected. It defines standards for exchanging authentication and authorization data between security domains. It is becoming increasingly important with cloud-based solutions and with Software-as-a-Service (SaaS) applications, because it ensures interoperability across identity providers. SAML is an XML-based protocol that uses security tokens and

assertions to pass information about a “principal” (typically an end user) with a SAML authority (an “identity provider” or IdP) and the service provider (SP). The principal requests a service from the SP which then requests and obtains an identity assertion from the IdP. The SP can then grant access or perform the requested service for the principal.

Chapter 7 Review

Chapter Summary After reading this chapter and completing the exercises, you should understand the following about PKI standards and protocols.

Identify the standards involved in establishing an interoperable Internet PKI

PKIX and PKCS define the most commonly used PKI standards.

PKIX, PKCS, X.509, ISAKMP, XKMS, and CMP combine to implement PKI.

SSL/TLS, S/MIME, HTTPS, and IPsec are protocols that use PKI.

Explain interoperability issues with PKI standards

Standards and protocols are important because they define the basis for

how communication will take place. The use of standards and protocols provides a common, interoperable environment for securely exchanging information.

Without these standards and protocols, two entities may independently develop their own method to implement the various components for a PKI, and the two will not be compatible.

On the Internet, not being compatible and not being able to communicate is not an option.

Describe how the common Internet protocols implement the PKI standards

Three main standards have evolved over time to implement PKIs on the Internet.

Two of the main standards are based on a third standard, the X.509 standard, and establish complementary standards for implementing PKIs. These two standards are Public Key Infrastructure X.509 (PKIX) and Public Key Cryptography Standards (PKCS).

PKIX defines standards for interactions and operations for four component types: the user (end-entity), certificate authority (CA), registration authority (RA), and the repository for certificates and certificate revocation lists (CRLs).

PKCS defines many of the lower-level standards for message syntax, cryptographic algorithms, and the like.

There are other protocols and standards that help define the management and operation of the PKI and related services, such as ISAKMP, XKMS, and CMP.

S/MIME is used to encrypt e-mail.

SSL, TLS, and WTLS are used for secure packet transmission.

IPsec is used to support virtual private networks.

The Common Criteria establishes a series of criteria from which security products can be evaluated.

The ISO/IEC 27002 standard provides a point from which security policies and practices can be developed in twelve areas.

Various types of publications are available from NIST such as those found in the FIPS series.

Key Terms certificate (172) certificate authority (CA) (169) certificate revocation list (CRL) (169) Internet Security Association and Key Management Protocol

(ISAKMP) (174) IPsec (182) Pretty Good Privacy (PGP) (180) public key infrastructure (PKI) (167) Secure/Multipurpose Internet Mail Extensions (S/MIME) (178) Secure Sockets Layer (SSL) (173) Security Assertion Markup Language (SAML) (185) Transport Layer Security (TLS) (173) Wireless Application Protocol (WAP) (184) Wireless Transport Layer Security (WTLS) (184) X.509 (172)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. _______________ is a protocol used to secure IP packets during

transmission across a network. It offers authentication, integrity, and confidentiality services. It uses Authentication Headers (AHs) and Encapsulating Security Payload (ESP) to accomplish this functionality.

2. An encryption capability designed to encrypt above the transport layer, enabling secure sessions between hosts, is called ______________.

3. A(n) _______________ is an entity that is responsible for issuing and revoking certificates. This term is also applied to server software that provides these services.

4. A digitally signed object that lists all of the current but revoked certificates issued by a given certificate authority is called the ______________. It allows users to verify whether a certificate is currently valid even if the expiration date hasn’t passed.

5. _______________ is a format that has been adopted to standardize digital certificates.

6. Infrastructure for binding a public key to a known user through a trusted intermediary, typically a certificate authority, is called the _______________.

7. The _______________ is a protocol framework that defines the mechanics of implementing a key exchange protocol and negotiation of a security policy.

8. The encryption protocol that is used on Wireless Application Protocol (WAP) networks is called _______________.

9. A protocol for transmitting data to small handheld devices like cellular phones is the _______________.

10. _______________ is a popular encryption program that has the ability to encrypt and digitally sign e-mail and files.

Multiple-Choice Quiz 1. Which of the following is used to grant permissions using rule-

based, role-based, and rank-based access controls?

A. A Qualified Certificate

B. A Control Certificate

C. An Attribute Certificate

D. An Optional Certificate

2. XKMS allows certificates to be all of the following except: A. Created

B. Registered

C. Managed

D. Revoked

3. Transport Layer Security consists of which two protocols? A. The TLS Record Protocol and TLS Handshake Protocol

B. The TLS Record Protocol and TLS Certificate Protocol

C. The TLS Certificate Protocol and TLS Handshake Protocol

D. The TLS Key Protocol and TLS Handshake Protocol

4. Which of the following provides a method for implementing a key exchange protocol?

A. EISA

B. ISAKMP

C. ISA

D. ISAKEY

5. Which of the following is a detailed standard for creating and implementing security policies?

A. PKIX

B. ISO/IEC 27002

C. FIPS

D. X.509

6. A relationship where two or more entities define how they will communicate securely is known as what?

A. A three-way handshake

B. A security association

C. A three-way agreement

D. A security agreement

7. What is the purpose of XKMS? A. Extends session associations over many transport protocols

B. Encapsulates session associations over TCP/IP

C. Defines services to manage heterogeneous PKI operations via XML

D. Designed to replace SSL

8. Which of the following is a secure e-mail standard? A. POP3

B. IMAP

C. SMTP

D. S/MIME

9. Which of the following is a joint set of security processes and standards used by approved laboratories to award an Evaluation Assurance Level (EAL) from EAL1 to EAL7?

A. Common Criteria

B. FIPS

C. ISO 17700

D. IEEE X.509

10. Transport Layer Security for HTTP uses what port to communicate? A. 53

B. 80

C. 143

D. 443

Essay Quiz 1. You are the Information Security Officer at a medium-sized

company (1500 employees). The CIO has asked you to explain why you recommend using commercial PKIs rather than implementing such a capability in-house with the software developers you already have. Write three succinct sentences that would get your point across and address three key issues.

2. Imagine you are a web developer for a small locally owned business. Explain when using HTTP would be satisfactory and why, and explain when you should use HTTPS and why.

3. Explain in your own words how, by applying both asymmetric and symmetric encryption, your browser uses TLS to protect the privacy of the information passing between your browser and a web server.

4. It is well understood that asymmetric encryption consumes more computing resources than symmetric encryption. Explain how PGP uses both asymmetric and symmetric encryption to be both secure and efficient.

Lab Projects

Note that for these lab projects, it would be best to have a partner so that you can each have your own pair of public/private keys to confirm the operation of PGP.

• Lab Project 7.1 Load either a trial version of PGP or Gnu Privacy Guard (GPG). Install it and create a public/private key pair for yourself. Create a document using a word processor and encrypt it using the receiver’s public key. Send it to a partner (or yourself) and then decrypt it using the corresponding private key.

• Lab Project 7.2 Create another document different from the one used in Lab Project 7.1. This time use your private key to digitally sign the document and send it to a partner (or yourself) who can then use the public key to confirm that it really is from the indicated sender.

chapter 8 Physical Security

Baseball is 90 percent mental, the other half is physical.

—YOGI BERRA

F

In this chapter, you will learn how to

Describe how physical security directly affects computer and network security

Discuss steps that can be taken to help mitigate risks

Identify the different types of fires and the various fire suppression systems designed to limit the damage caused by fires

Explain electronic access controls and the principles of convergence

or most homes, locks are the primary means of achieving physical security, and almost everyone locks the doors to his or her home upon leaving the residence. Some go even further and set up intrusion alarm

systems in addition to locks. All these precautions are considered necessary because people believe they have something significant inside the house that needs to be protected, such as important possessions and important people. Physical security is an important topic for businesses dealing with the

security of networks and information systems. Businesses are responsible for securing their profitability, which requires securing a combination of assets: employees, product inventory, trade secrets, and strategy information. These and other important assets affect the profitability of a company and its future survival. Companies therefore perform many activities to attempt to provide physical security—locking doors, installing alarm systems, using safes, posting security guards, setting access controls, and more. Most companies today have invested a large amount of time, money,

and effort in both network security and information systems security. In this chapter, you will learn about how the strategies for securing the network and for securing information systems are linked, and you’ll learn several methods by which companies can minimize their exposure to physical security events that can diminish their network security.

The Security Problem The problem that faces professionals charged with securing a company’s network can be stated rather simply: physical access negates all other security measures. No matter how impenetrable the firewall and intrusion detection system (IDS), if an attacker can find a way to walk up to and touch a server, he can break into it. Consider that most network security measures are, from necessity,

directed at protecting a company from Internet-based threats. Consequently, a lot of companies allow any kind of traffic on the local area network (LAN). So if an attacker attempts to gain access to a server over the Internet and fails, he may be able to gain physical access to the receptionist’s machine and, by quickly compromising it, use it as a remotely controlled zombie to attack what he is really after. Figure 8.1 illustrates the use of a lower-privilege machine to obtain sensitive information. Physically securing information assets doesn’t mean just the servers; it means protecting physical access to all the organization’s computers and its entire network infrastructure.

• Figure 8.1 Using a lower-privilege machine to get at sensitive information

Physical access to a corporation’s systems can allow an attacker to perform a number of interesting activities, starting with simply plugging into an open Ethernet jack. The advent of handheld devices with the ability to run operating systems with full networking support has made this attack scenario even more feasible. Prior to handheld devices, the attacker would have to work in a secluded area with dedicated access to the Ethernet for a time. The attacker would sit down with a laptop and run a variety of tools against the network, and working internally typically put the attacker inside the firewall and IDS. Today’s capable mobile devices can assist these efforts by allowing attackers to place the small device onto the network to act as a wireless bridge, as shown in Figure 8.2.

• Figure 8.2 A wireless bridge can allow remote access.

The attacker can then use a laptop to attack a network remotely via the bridge from outside the building. If power is available near the Ethernet jack, this type of attack can also be accomplished with an off-the-shelf access point. The attacker’s only challenge is finding an Ethernet jack that

isn’t covered by furniture or some other obstruction. Another simple attack that can be used when an attacker has physical

access is called a bootdisk. Any media used to boot a computer into an operating system that is not the native OS on its hard drive could be classified as a bootdisk. These can be in the form of a floppy disk, CD, DVD, or a USB flash drive. Before bootable CDs or DVDs were available, a boot floppy was used to start the system and prepare the hard drives to load the operating system. A boot source can contain a number of programs, but the most typical ones would be NTFSDOS or a floppy- based Linux distribution that can be used to perform a number of tasks, including mounting the hard drives and performing at least read operations, all done via script. Once an attacker is able to read a hard drive, the password file can be copied off the machine for offline password-cracking attacks. If write access to the drive is obtained, the attacker could alter the password file or place a remote-control program to be executed automatically upon the next boot, guaranteeing continued access to the machine. Most new machines do not include floppy drives, so this attack is rapidly being replaced by the same concept with a USB device, CD, or DVD. The most obvious mitigation is to tell the BIOS not to boot from removable media, but this too has issues. The bootable CD-ROMs and DVD-ROMs are actually more of a threat,

because they are frequently used to carry a variety of software for updates and can utilize the much greater storage capacity of the CD or DVD media. This capacity can store an entire operating system and a complete tool set for a variety of tasks or malware, so when updating via CD/DVD, precautions must be taken to ensure the veracity of the media. There are operating system distributions specifically designed to run the

entire machine from an optical disc without using the hard drive. These are commonly referred to as LiveCDs. A LiveCD contains a bootable version of an entire operating system, typically a variant of Linux, complete with drivers for most devices. LiveCDs give an attacker a greater array of tools than could be loaded onto a floppy disk, such as scanners, sniffers, vulnerability exploits, forensic tools, drive imagers, password crackers,

and so on. These sets of tools are too numerous to list here and are changing every day. The best resource is to search the Internet for popular LiveCD distributions like Kali/Backtrack, knoppix, and PHLAK. A sample collection of LiveCDs is shown in Figure 8.3.

• Figure 8.3 A collection of sample LiveCDs

For example, with a LiveCD an attacker would likely have access to the hard disk and also to an operational network interface that would allow

him to send the drive data over the Internet if properly connected. These bootable operating systems could also be custom built to contain any tool that runs under Linux, allowing an attacker to build a standard bootable attack image or a standard bootable forensic image, or something customized for the tools he likes to use. Bootable USB flash drives emulate the function of a CD-ROM and provide a device that is both physically smaller and logically larger. Cheap USB flash drives are now commonly available that provide greater than 32GB of storage, with more expensive versions stretching that capacity to 64, 128, and even 256GB. Electronic miniaturization has made these devices small enough to be unnoticed; a recent version extends only 5mm from the USB port. Made bootable, these devices can contain entire specialized operating systems, and unlike a bootable CD-ROM, these devices can also be written to, providing an offload point for collected data if an attacker chooses to leave the device and return later.

Try This! Create a Bootdisk Bootdisks allow you to boot a computer to the disk rather than the OS that is on the hard drive. Create a bootdisk for your own personal computer. The steps differ between different OSs and depending upon the media that you wish to make bootable. Perform a little research to determine the correct procedure for your OS and give it a try. Make a bootable CD/DVD or USB flash drive.

These types of devices have spawned a new kind of attack in which a CD, DVD, or flash drive is left in an opportunistic place where members of a target organization may pick up and use them. This CD/DVD or flash drive is typically loaded with malware and is referred to as a road apple. The attack relies on curious people to plug the device into their work computer to see what’s on it. Occasionally the attacker may also try to tempt the passerby with enticing descriptions like “Employee Salaries” or even something as simple as “Confidential.” Once a user loads the CD/DVD or flash drive, the malware will attempt to infect the machine.

Drive imaging is the process of copying the entire contents of a hard drive to a single file on a different media. This process is often used by people who perform forensic investigations of computers. Typically, a bootable media is used to start the computer and load the drive imaging software. This software is designed to make a bit-by-bit copy of the hard drive in a file on another media, usually another hard drive or CD-R/DVD-R media. Drive imaging is used in investigations to make an exact copy that can be observed and taken apart, while keeping the original exactly as it was for evidence purposes.

Exam Tip: Drive imaging is a threat because all existing access controls to data can be bypassed and all the data stored on the drive can be read from the image.

From an attacker’s perspective, drive imaging software is useful because it pulls all information from a computer’s hard drive while still leaving the machine in its original state. The information contains every bit of data that is on the computer: any locally stored documents, locally stored e- mails, and every other piece of information that the hard drive contains. This data could be very valuable if the machine holds sensitive information about the company. Physical access is the most common way of imaging a drive, and the

biggest benefit for the attacker is that drive imaging leaves absolutely no trace of the crime. Besides physically securing access to your computers, you can do very little to prevent drive imaging, but you can minimize its impact. The use of encryption even for a few important files provides protection. Full encryption of the drive protects all files stored on it. Alternatively, placing files on a centralized file server keeps them from being imaged from an individual machine, but if an attacker is able to image the file server, the data will be copied.

Cross Check Forensic Images When taking a forensic-based image, it is important to follow proper forensic procedures to ensure the evidence is properly secured. Forensic processes and procedures are covered in detail in Chapter 23.

Tech Tip

Encryption to TPM-Based Keys Many computers now come with a security chip that follows the Trusted Platform Module standard. This TPM chip allows for the creation and storage of encryption keys. One of the strengths associated with this level of security is that if a copy of a drive, or even the drive itself, is stolen, the contents are unusable without the key. Having this key locked in hardware prevents hackers from stealing a copy of the key from a memory location.

A denial-of-service (DoS) attack can also be performed with physical access. Physical access to the computers can be much more effective than a network-based DoS attack. Stealing a computer, using a bootdisk to erase all data on the drives, or simply unplugging computers are all effective DoS attacks. Depending on the company’s quality and frequency of backing up critical systems, a DoS attack using these methods can have lasting effects. Physical access can negate almost all the security that the network

attempts to provide. Considering this, you must determine the level of physical access that attackers might obtain. Of special consideration are persons with authorized access to the building but who are not authorized users of the systems. Janitorial personnel and others have authorized access to many areas, but they do not have authorized system access. An attacker could pose as one of these individuals or attempt to gain access to the facilities through them.

Physical Security Safeguards While it is difficult, if not impossible, to make an organization’s computer systems totally secure, many steps can be taken to mitigate the risk to information systems from a physical threat. The following sections discuss access control methods and physical security policies and procedures that should be implemented.

Walls and Guards The primary defense against a majority of physical attacks are the barriers between the assets and a potential attacker—walls, fences, gates, and doors. Some organizations also employ full- or part-time private security staff to attempt to protect their assets. These barriers provide the foundation upon which all other security initiatives are based, but the security must be designed carefully, as an attacker has to find only a single gap to gain access.

Exam Tip: All entry points to server rooms and wiring closets should be closely controlled, and, if possible, access should be logged through an access control system.

Walls may have been one of the first inventions of man. Once he learned to use natural obstacles such as mountains to separate him from his enemy, he next learned to build his own mountain for the same purpose. Hadrian’s Wall in England, the Great Wall of China, and the Berlin Wall are all famous examples of such basic physical defenses. The walls of any building serve the same purpose, but on a smaller scale: they provide barriers to physical access to company assets. Bollards are small and round concrete pillars that are constructed and placed around a building to protect it from being damaged by someone driving a vehicle into the side of the building, or getting close and using a car bomb.

To protect the physical servers, you must look in all directions: Doors and windows should be safeguarded and a minimum number of each should be used in a server room. Less obvious entry points should also be considered: Is a drop ceiling used in the server room? Do the interior walls extend to the actual roof, raised floors, or crawlspaces? Access to the server room should be limited to the people who need access, not to all employees of the organization. If you are going to use a wall to protect an asset, make sure no obvious holes appear in that wall.

Another method of preventing surreptitious access is through the use of windows. Many high- security areas have a significant number of windows so that people’s activities within the area can’t be hidden. A closed server room with no windows makes for a quiet place for someone to achieve physical access to a device without worry of being seen. Windows remove this privacy element that many criminals depend upon to achieve their entry and illicit activities. Too many windows makes it easy to shoulder surf — balance is the key,

Fences Outside of the building’s walls, many organizations prefer to have a perimeter fence as a physical first layer of defense. Chain-link-type fencing is most commonly used, and it can be enhanced with barbed wire. Anti-scale fencing, which looks like very tall vertical poles placed close together to form a fence, is used for high-security implementations that require additional scale and tamper resistance. To increase security against physical intrusion, higher fences can be

employed. A fence that is three to four feet in height will deter casual or accidental trespassers. Six to seven feet will deter a general intruder. To deter more determined intruders, a minimum height of eight feet is recommended with the addition of barbed wire or razor wire on top for extreme levels of deterrence.

Guards

Guards provide an excellent security measure, because guards are a visible presence with direct responsibility for security. Other employees expect security guards to behave a certain way with regard to securing the facility. Guards typically monitor entrances and exits and can maintain access logs of who has entered and departed the building. In many organizations, everyone who passes through security as a visitor must sign the log, which can be useful in tracing who was at what location and why.

The bigger challenge associated with capturing surveillance activities or other attempted break-in efforts is their clandestine nature. These efforts are designed to be as low profile and nonobvious as possible to increase the chances of success. Training and awareness is necessary not just for security personnel but for all personnel. If an employee hears multiple extensions all start ringing in the middle of the night, do they know who to notify? If a security guard notes such activity, how does this information get reported to the correct team?

Security personnel are helpful in physically securing the machines on which information assets reside, but to get the most benefit from their presence, they must be trained to take a holistic approach to security. The value of data typically can be many times that of the machines on which the data is stored. Security guards typically are not computer security experts, so they need to be educated about the value of the data and be trained in network security as well as physical security involving users. They are the company’s eyes and ears for suspicious activity, so the network security department needs to train them to notice suspicious network activity as well. Multiple extensions ringing in sequence during the night, computers rebooting all at once, or strange people parked in the parking lot with laptop computers are all indicators of a network attack that might be missed without proper training. Many traditional physical security tools such as access controls and

CCTV camera systems are transitioning from closed hardwired systems to Ethernet- and IP-based systems. This transition opens up the devices to network attacks traditionally performed on computers. With physical security systems being implemented using the IP network, everyone in

physical security must become smarter about network security.

Physical Access Controls and Monitoring Physical access control means control of doors and entry points. The design and construction of all types of access control systems, as well as the physical barriers to which they are most complementary, are fully discussed in other texts. Here, we explore a few important points to help you safeguard the information infrastructure, especially where it meets with the physical access control system. This section talks about physical locks, layered access systems, and electronic access control systems. It also discusses closed circuit television (CCTV) systems and the implications of different CCTV system types.

Locks Locks have been discussed as a primary element of security. Although locks have been used for hundreds of years, their design has not changed much: a metal “token” is used to align pins in a mechanical device. As all mechanical devices have tolerances, it is possible to sneak through these tolerances by “picking” the lock. Most locks can be easily picked with simple tools, some of which are shown in Figure 8.4.

• Figure 8.4 Lockpicking tools

As we humans are always trying to build a better mousetrap, high- security locks have been designed to defeat attacks, such as the one shown in Figure 8.5; these locks are more sophisticated than a standard home deadbolt system. Typically found in commercial applications that require high security, these locks are made to resist picking and drilling, as well as other common attacks such as simply pounding the lock through the door. Another common feature of high-security locks is key control, which refers to the restrictions placed on making a copy of the key. For most residential locks, a trip to the hardware store will allow you to make a copy of the key. Key control locks use patented keyways that can only be copied at a locksmith, who will keep records on authorized users of a particular key.

• Figure 8.5 A high-security lock and its key

High-end lock security is more important now that attacks such as “bump keys” are well known and widely available. A bump key is a key cut with all notches to the maximum depth, also known as “all nines.” This key uses a technique that has been around a long time, but has recently gained a lot of popularity. The key is inserted into the lock and then sharply struck, bouncing the lock pins up above the shear line and allowing the lock to open. High-security locks attempt to prevent this type of attack through various mechanical means such as nontraditional pin layout, sidebars, and even magnetic keys. Other physical locks include programmable or cipher locks; locks with a

keypad that require a combination of keys to open the lock; and locks with a reader that require an access card to open the lock. These may have special options such as a hostage alarm (support a key combination to trigger an alarm). Master-keying (support key combinations to change the access code and configure the functions of the lock) and key-override functions (support key combinations to override the usual procedures) are also options on high-end programmable locks.

Exam Tip: Layered access is a form of defense in depth, a principle component of any strong security solution.

Device locks are used to lock a device to a physical restraint, preventing its removal. Another method of securing laptops and mobile devices is a cable trap, which allows a user to affix a cable lock to a secure structure.

Layered Access Layered access is an important concept in security. It is often mentioned in conversations about network security perimeters, but in this chapter it relates to the concept of physical security perimeters. To help prevent an attacker from gaining access to important assets, these assets should be placed inside multiple perimeters. Servers should be placed in a separate secure area, ideally with a separate authentication mechanism. For example, if an organization has an electronic door control system using contactless access cards (such as the example shown in Figure 8.6) as well as a keypad, a combination of the card and a separate PIN code would be required to open the door to the server room.

• Figure 8.6 Contactless access cards act as modern keys to a building.

Access to the server room should be limited to staff with a legitimate need to work on the servers. To layer the protection, the area surrounding

the server room should also be limited to people who need to work in that area.

Electronic Access Control Systems Many organizations use electronic access control systems to control the opening of doors. The use of proximity readers and contactless access cards provides user information to the control panel. Doorways are electronically controlled via electronic door strikes and magnetic locks. These devices rely on an electronic signal from the control panel to release the mechanism that keeps the door closed. These devices are integrated into an access control system that controls and logs entry into all the doors connected to it, typically through the use of access tokens. Security is improved by having a centralized system that can instantly grant or refuse access based upon access lists and the reading of a token that is given to the user. This kind of system also logs user access, providing nonrepudiation of a specific user’s presence in a controlled environment. The system will allow logging of personnel entry, auditing of personnel movements, and real-time monitoring of the access controls.

Exam Tip: A mantrap door arrangement can prevent unauthorized people from following authorized users through an access-controlled door, which is also known as “tailgating.”

One caution about these kinds of systems is that they usually work with a software package that runs on a computer, and as such this computer should not be attached to the company network. While attaching it to the network can allow easy administration, the last thing you want is for an attacker to have control of the system that allows physical access to your facility. With this control, an attacker could input the ID of a badge that she owns, allowing full, legitimate access to an area the system controls. Another problem with such a system is that it logs only the person who initially used the card to open the door—so no logs exist for doors that are

propped open to allow others access, or of people “tailgating” through a door opened with a card. The implementation of a mantrap is one way to combat tailgating. A mantrap comprises two doors closely spaced that require the user to card through one and then the other sequentially. Mantraps make it nearly impossible to trail through a doorway undetected —if you happen to catch the first door, you will be trapped in by the second door.

Doors Doors to secured areas should have characteristics to make them less obvious. They should have similar appearance to the other doors to avoid catching the attention of intruders. Security doors should be self-closing and have no hold-open feature. They should trigger alarms if they are forcibly opened or have been held open for a long period.

Exam Tip: A fail-soft (or fail-safe) lock is unlocked in a power interruption. A fail-secure lock is locked in a power interruption.

Door systems, like many systems, have two design methodologies: fail- safe or fail-secure. While fail-safe is a common enough phrase to have entered the lexicon, think about what it really means—being safe when a system fails. In the case of these electronic door systems, fail-safe means that the door is unlocked should power fail. To fail-secure means that the system will lock the door when power is lost. This can also apply when door systems are manually bypassed. It is important to know how each door will react to a system failure, not only for security but also for fire code compliance, as fail-secure is not allowed for certain doors in a building.

Cameras

Closed circuit television (CCTV) cameras are similar to the door control systems—they can be very effective, but how they are implemented is an important consideration. The use of CCTV cameras for surveillance purposes dates back to at least 1961, when cameras were installed in the London Transport train station. The development of smaller and more sophisticated camera components and decreasing prices for the cameras have caused a boon in the CCTV industry since then. CCTV cameras are used to monitor a workplace for security purposes.

These systems are commonplace in banks and jewelry stores, places with high-value merchandise that is attractive to thieves. As the expense of these systems dropped, they became practical for many more industry segments. Traditional cameras are analog based and require a video multiplexer to combine all the signals and make multiple views appear on a monitor. IP-based cameras are changing that, as most of them are standalone units viewable through a web browser, such as the camera shown in Figure 8.7.

• Figure 8.7 IP-based cameras leverage existing IP networks instead of needing a proprietary CCTV cable.

Tech Tip

PTZ Cameras Pan-tilt-zoom (PTZ) cameras are cameras that have the functionality to enable camera movement in multiple axes, as well as the ability to zoom in on an item. These cameras provide additional capability, especially in situations where the video is monitored and the

monitoring station can maneuver the camera.

These IP-based systems add useful functionality, such as the ability to check on the building from the Internet. This network functionality, however, makes the cameras subject to normal IP-based network attacks. A DoS attack launched at the CCTV system just as a break-in is occurring is the last thing that anyone would want (other than the criminals). For this reason, IP-based CCTV cameras should be placed on their own separate network that can be accessed only by security personnel. The same physical separation applies to any IP-based camera infrastructure. Older time-lapse tape recorders are slowly being replaced with digital video recorders. While the advance in technology is significant, be careful if and when these devices become IP-enabled, since they will become a security issue, just like everything else that touches the network. If you depend on the CCTV system to protect your organization’s

assets, carefully consider camera placement and the type of cameras used. Different iris types, focal lengths, and color or infrared capabilities are all options that make one camera superior to another in a specific location.

Alarms There are several types of alarm systems. Local alarm systems ring only locally. A central station system is one where alarms (and CCTV) are monitored by a central station. Many alarms will have auxiliary or secondary reporting functions to local police or fire departments. Alarms work by alerting personnel to the triggering of specific monitoring controls. Typical controls include the following:

Dry contact switches use metallic foil tape as a contact detector to detect whether a door or window is opened.

Electro-mechanical detection systems detect a change or break in a circuit. They can be used as a contact detector to detect whether a door or window is opened.

Vibration detection systems detect movement on walls, ceiling, floors, and so forth by vibration.

Pressure mats detect whether someone is stepping on the mat.

Photoelectric or photometric detection systems emit a beam of light and monitor the beam to detect for motion and break-in.

Wave pattern motion detectors generate microwave or ultrasonic wave and monitor the emitted waves to detect for motion.

Passive infrared detection systems detect changes of heat waves generated by an intruder.

Audio or acoustical-seismic detection systems listen for changes in noise levels.

Proximity detectors or capacitance detectors emit a magnetic field and monitor the field to detect any interruption.

Convergence There is a trend to converge elements of physical and information security to improve identification of unauthorized activity on networks. If a access control system is asked to approve access to an insider using an outside address, yet the physical security system identifies them as being in the building, then an anomaly exists and should be investigated. This trend is called convergence and can significantly improve defenses against cloned credentials.

Policies and Procedures A policy’s effectiveness depends on the culture of an organization, so all of the policies mentioned here should be followed up by functional procedures that are designed to implement them. Physical security policies and procedures relate to two distinct areas: those that affect the computers themselves and those that affect users.

To mitigate the risk to computers, physical security needs to be extended to the computers themselves. To combat the threat of bootdisks, begin by removing or disabling the ability of a system to automatically play connected devices, such as USB flash drives. Other activities that typically require physical presence should be protected, such as access to a system’s BIOS at bootup.

Try This! Exploring Your BIOS Settings Next time you boot your PC, explore the BIOS settings. Usually, pressing the F2 key immediately on power-up will allow you to enter the BIOS setup screens. Most PCs will also have a brief time when they prompt for “Setup” and give a key to press, most commonly F2, or F12. Explore elements such as the boot order for devices, options for adding passwords, and other options. For safety, do not save changes unless you are absolutely certain that you want to make those changes and are aware of the consequences. To prevent an attacker from editing the boot order, you should set BIOS passwords.

BIOS A safeguard that can be employed is the removal of removable media devices from the boot sequence in the computer’s BIOS (basic input/output system). The specifics of this operation depend on the BIOS software of the individual machine. A related step that must be taken is to set a BIOS password. Nearly all BIOS software will support password protection that allows you to boot the machine but requires a password to edit any BIOS settings. While disabling the optical drive and setting a BIOS password are both good measures, do not depend on this strategy exclusively because, in some cases, BIOS manufacturers will have a default BIOS password that still works.

Depending upon BIOS passwords is also not a guaranteed security measure. For many machines,

it is trivial to remove and then replace the BIOS battery, which will reset the BIOS to the “no password” or default password state.

UEFI Unified Extensible Firmware Interface (UEFI) is a standard firmware interface for PCs, designed to replace BIOS. Supported by Mac OS X, Linux (later versions), and Windows 8 and beyond, UEFI offers some significant security advantages. UEFI has a functionality known as secure boot, which allows only digitally signed drivers and OS loaders to be used during the boot process, preventing bootkit attacks. As UEFI is replacing BIOS, and has additional characteristics, it is important to keep policies and procedures current with the advancement of technology.

Exam Tip: USB devices can be used to inject malicious code onto any machine to which they are attached. They can be used to transport malicious code from machine to machine without using the network.

USB USB ports have greatly expanded users’ ability to connect devices to their computers. USB ports automatically recognize a device being plugged into the system and usually work without the user needing to add drivers or configure software. This has spawned a legion of USB devices, from MP3 players to CD burners. The most interesting of these, for security purposes, are the USB flash

memory–based storage devices. USB drive keys, which are basically flash memory with a USB interface in a device typically about the size of your thumb, provide a way to move files easily from computer to computer. When plugged into a USB port, these devices automount and behave like any other drive attached to the computer. Their small size and relatively large capacity, coupled with instant read-write ability, present security

problems. They can easily be used by an individual with malicious intent to conceal the removal of files or data from the building or to bring malicious files into the building and onto the company network.

Laptops and tablets are popular targets for thieves and should be locked inside a desk when not in use, or secured with special computer lockdown cables. If desktop towers are used, use computer desks that provide a space in which to lock the computer. All of these measures can improve the physical security of the computers themselves, but most of them can be defeated by attackers if users are not knowledgeable about the security program and do not follow it.

In addition, well-intentioned users could accidentally introduce malicious code from USB devices by using them on an infected home machine and then bringing the infected device to the office, allowing the malware to bypass perimeter protections and possibly infect the organization. If USB devices are allowed, aggressive virus scanning should be implemented throughout the organization. The devices can be disallowed via Active Directory policy settings or with a Windows Registry key entry. USB can also be completely disabled, either through BIOS settings or by unloading and disabling the USB drivers from users’ machines, either of which will stop all USB devices from working— however, doing this can create more trouble if users have USB keyboards and mice. There are two common ways to disable USB support in a Windows system. On older systems, editing the Registry key is probably the most effective solution for users who are not authorized to use these devices. On newer systems, the best way is through Group Policy in a domain or through the Local Security Policy MMC on a stand-alone box.

Autoplay Another boot device to consider is the CD/DVD drive. This device can probably also be removed from or disabled on a number of machines. A DVD not only can be used as a boot device, but also can be exploited via

the autoplay feature that some operating systems support. Autoplay was designed as a convenience for users, so that when a CD/DVD or USB containing an application is inserted, the computer instantly prompts for input versus requiring the user to explore the device filesystem and find the executable file. Unfortunately, since the autoplay functionality runs an executable, it can be programmed to do anything an attacker wants. If an autoplay executable is malicious, it could allow an attacker to gain remote control of the machine. Figure 8.8 illustrates an autoplay message prompt in Windows, giving a user at least minimal control over whether to run an item or not.

• Figure 8.8 Autoplay on a Windows system

Since the optical drive can be used as a boot device, a DVD loaded with

its own operating system (called a LiveCD, introduced earlier in the chapter) could be used to boot the computer with malicious system code (see Figure 8.9). This separate operating system will bypass any passwords on the host machine and can access locally stored files.

• Figure 8.9 A LiveCD boots its own OS and bypasses any built-in security of the native operating system.

Tech Tip

Disabling the Autoplay Feature in Windows Disabling the autoplay feature is an easy task using Local Group Policy Editor in Windows. Simply launch the Local Group Policy Editor (gpedit.msc) and navigate to this location:

Computer Configuration > Administrative Templates > Windows Components > AutoPlay Policies

Device Theft The outright theft of a computer is a simple physical attack. This attack can be mitigated in a number of ways, but the most effective method is to lock up equipment that contains important data. Insurance can cover the loss of the physical equipment, but this can do little to get a business up and running again quickly after a theft. Therefore, implementing special access controls for server rooms and simply locking the rack cabinets when maintenance is not being performed are good ways to secure an area. From a data standpoint, mission-critical or high-value information should be stored on a server only. This can mitigate the risk of a desktop or laptop being stolen for the data it contains. Loss of laptops has been a common cause of information breaches.

Mobile device thefts from cars and other locations can occur in seconds. Thieves have been caught taking mobile devices from security screening areas at airports while the owner was distracted in screening. Snatch and grab attacks occur in restaurants, bars, and cafes. Tablets and smartphones have significant value and physical precautions should be taken at all times.

Cross Check Mobile Device Security Mobile device security is covered in depth in Chapter 14. For a more detailed analysis of safeguards unique to mobile devices, please refer to that section of the text.

Users can perform one of the most simple, yet important, information security tasks: lock a workstation immediately before they step away from it.

Although use of a self-locking screensaver is a good policy, setting it to lock at any point less than 10 to 15 minutes after becoming idle is often considered a nuisance and counterproductive to active use of the computer on the job as the computer will often lock while the employee is still actively using the computer. Thus, computers typically sit idle for at least 15 minutes before automatically locking under this type of policy. Users should manually lock their workstations, as an attacker only needs to be lucky enough to catch a machine that has been left alone for 5 minutes.

BTU stands for British Thermal Unit; a single BTU is defined as the amount of energy required to raise the temperature of one pound of liquid water one degree Fahrenheit.

Environmental Controls While the confidentiality of information is important, so is its availability. Sophisticated environmental controls are needed for current data centers. Servers can generate large levels of heat, and managing the heat is the job of the environmental control. Controlling a data center’s temperature and humidity is important to

keeping servers running. Heating ventilating and air conditioning (HVAC) systems are critical for keeping data centers cool, because typical servers put out between 1000 and 2000 BTUs of heat. The temperature of a data center should be maintained between 70 and 74 degrees Fahrenheit (°F). If the temperature is too low, it may cause mechanisms to slow down. If the temperature is too high, it may cause equipment damage. The temperature- damaging points of different products are as follows:

Magnetic media: 100°F

Computer hardware: 175°F

Paper products: 350°F

It should be noted that these are temperatures of the materials; the surrounding air is frequently cooler. Temperature measurements should be obtained on equipment itself to ensure appropriate protection. Multiple servers in a confined area can create conditions too hot for the

machines to continue to operate. This problem is made worse with the advent of blade-style computing systems and with many other devices shrinking in size. While physically smaller, they tend to still expel the same amount of heat. This is known as increased data center density —more servers and devices per rack, putting a greater load on the cooling systems. This encourages the use of a hot aisle/cold aisle layout. A data center that is arranged into hot and cold aisles dictates that all the intake fans on all equipment face the cold aisle, and the exhaust fans all face the opposite aisle. The HVAC system is then designed to push cool air underneath the raised floor and up through perforated tiles on the cold aisle. Hot air from the hot aisle is captured by return air ducts for the HVAC system. The use of this layout is designed to control airflow, with the purpose being never to mix the hot and cold air. This requires the use of blocking plates and side plates to close open rack slots. The benefits of this arrangement are that cooling is more efficient and can handle higher density. The failure of HVAC systems for any reason is cause for concern. Rising copper prices have made HVAC systems the targets for thieves, and general vandalism can result in costly downtime. Properly securing these systems is important in helping prevent an attacker from performing a physical DoS attack on your servers.

Fire Suppression According to the Fire Suppression Systems Association (www.fssa.net), 43 percent of businesses that close as a result of a significant fire never reopen. An additional 29 percent fail within three years of the event. The ability to respond to a fire quickly and effectively is thus critical to the long-term success of any organization. Addressing potential fire hazards and vulnerabilities has long been a concern of organizations in their risk

analysis process. The goal obviously should be never to have a fire, but in the event that one does occur, it is important that mechanisms are in place to limit the damage the fire can cause.

Tech Tip

Environment and Fires While it may at first seem to the security professional that environmental controls and natural disasters such as fires don’t have anything to do with computer security, think of it in terms of availability. If the goal of the attacker is not information but rather to deny an organization the use of its resources, environmental factors, and disasters such as fires, can be used to deny the target the use of its own computing resources. This, then, becomes a security issue as well as an operational issue.

Water-Based Fire Suppression Systems Water-based fire suppression systems have long been, and still are today, the primary tool to address and control structural fires. Considering the amount of electrical equipment found in today’s office environment and the fact that, for obvious reasons, this equipment does not react well to large applications of water, it is important to know what to do with equipment if it does become subjected to a water-based sprinkler system. The National Fire Protection Association’s 2013 NFPA 75: Standard for the Protection of Information Technology Equipment outlines measures that can be taken to minimize the damage to electronic equipment exposed to water. This guidance includes these suggestions:

Open cabinet doors, remove side panels and covers, and pull out chassis drawers to allow water to run out of equipment.

Set up fans to move room-temperature air through the equipment for general drying. Move portable equipment to dry air-conditioned areas.

Use compressed air at no higher than 50 psi to blow out trapped water.

Use handheld dryers on lowest setting to dry connectors, backplane wirewraps, and printed circuit cards.

Use cotton-tipped swabs for hard-to-reach places. Lightly dab the surfaces to remove residual moisture.

Keep the dryers well away from components and wires. Overheating of electrical components can cause permanent damage.

Even if these guidelines are followed, damage to the systems may have already occurred. Since water is so destructive to electronic equipment, not only because of the immediate problems of electronic shorts to the system but also because of longer-term corrosive damage water can cause, alternative fire suppression methods have been sought.

Halon-Based Fire Suppression Systems A fire needs fuel, oxygen, and high temperatures for the chemical combustion to occur. If you remove any of these, the fire will not continue. Halon interferes with the chemical combustion present in a fire. Even though halon production was banned in 1994, a number of these systems still exist today. They were originally popular because halon will mix quickly with the air in a room and will not cause harm to computer systems. Halon is, however, dangerous to humans, especially when subjected to extremely hot temperatures (such as might be found during a fire), when it can degrade into other toxic chemicals. As a result of these dangers, and also because halon has been linked with the issue of ozone depletion, halon is banned in new fire suppression systems. It is important to note that under the Environmental Protection Agency (EPA) rules that mandated no further production of halon, existing systems were not required to be destroyed. Replacing the halon in a discharged system,

however, will be a problem, since only existing stockpiles of halon may be used and the cost is becoming prohibitive. For this reason, many organizations are switching to alternative solutions.

Tech Tip

Drills In the event of an emergency, people will be challenged to perform correct actions when stressed by the emergency. The use of drills, plans, and testing will ensure that escape plans and escape routes are known and effective and that people are familiar with their use. The time to practice is before the problem, and repeating practice over time builds confidence and strengthens familiarity.

Clean-Agent Fire Suppression Systems These alternatives are known as clean-agent fire suppression systems, since they not only provide fire suppression capabilities but also protect the contents of the room, including people, documents, and electronic equipment. Examples of clean agents include carbon dioxide, argon, Inergen, and FM-200 (heptafluoropropane). Carbon dioxide (CO2) has been used as a fire suppression agent for a long time. The Bell Telephone Company used portable CO2 extinguishers in the early part of the 20th century. Carbon dioxide extinguishers attack all three necessary elements for a fire to occur. CO2 displaces oxygen so that the amount of oxygen remaining is insufficient to sustain the fire. It also provides some cooling in the fire zone and reduces the concentration of “gasified” fuel. Argon extinguishes fire by lowering the oxygen concentration below the 15 percent level required for combustible items to burn. Argon systems are designed to reduce the oxygen content to about 12.5 percent, which is below the 15 percent needed for the fire but is still above the 10 percent required by the EPA for human safety. Inergen, a product of Ansul Corporation, is composed of three gases: 52 percent nitrogen, 40 percent

argon, and 8 percent carbon dioxide. In a manner similar to pure argon systems, Inergen systems reduce the level of oxygen to about 12.5 percent, which is sufficient for human safety but not sufficient to sustain a fire. Another chemical used in the phase-out of halon is FE-13, or trifluoromethane. This chemical was originally developed as a chemical refrigerant and works to suppress fires by inhibiting the combustion chain reaction. FE-13 is gaseous, leaves behind no residue that would harm equipment, and is considered safe to use in occupied areas. Other halocarbons are also approved for use in replacing halon systems, including FM-200 (heptafluoropropane), a chemical used as a propellant for asthma medication dispensers.

Handheld Fire Extinguishers Automatic fire suppression systems designed to discharge when a fire is detected are not the only systems you should be aware of. If a fire can be caught and contained before the automatic systems discharge, it can mean significant savings to the organization in terms of both time and equipment costs (including the recharging of the automatic system). Handheld extinguishers are common in offices, but the correct use of them must be understood or disaster can occur. There are four different types of fire, as shown in Table 8.1. Each type of fire has its own fuel source and method for extinguishing it. Type A systems, for example, are designed to extinguish fires with normal combustible material as the fire’s source. Water can be used in an extinguisher of this sort, since it is effective against fires of this type. Water, as we’ve discussed, is not appropriate for fires involving wiring or electrical equipment. Using a type A extinguisher against an electrical fire will not only be ineffective but can result in additional damage. Some extinguishers are designed to be effective against more than one type of fire, such as the common ABC fire extinguishers. This is probably the best type of system to have in a data processing facility. All fire extinguishers should be easily accessible and should be clearly marked. Before anybody uses an extinguisher, they should know

what type of extinguisher it is and what the source of the fire is. When in doubt, evacuate and let the fire department handle the situation.

Table 8.1 Types of Fire and Suppression Methods

Exam Tip: The type of fire distinguishes the type of extinguisher that should be used to suppress it. Remember that the most common type is the ABC fire extinguisher, which is designed to handle all types of fires except flammable-metal fires, which are rare.

Try This! Handheld Fire Extinguishers Computer security professionals typically do not have much influence over the type of fire suppression system that their office includes. It is, however, important that they are aware of what type has been installed, what they should do in case of an emergency, and what needs to be done to recover after the release of the system. One area that they can influence, however, is the type of handheld fire extinguisher that is located in their area. Check your facility to see what type of fire suppression system is installed. Also check to see where the fire extinguishers are in your office and what type of fires they are designed to handle.

Fire Detection Devices An essential complement to fire suppression systems and devices are fire detection devices (fire detectors). Detectors may be able to detect a fire in its very early stages, before a fire suppression system is activated, and sound a warning that potentially enables employees to address the fire before it becomes serious enough for the fire suppression equipment to kick in. There are several different types of fire detectors. One type, of which

there are two varieties, is activated by smoke. The two varieties of smoke detector are ionization and photoelectric. A photoelectric detector is good for potentially providing advance warning of a smoldering fire. This type of device monitors an internal beam of light. If something degrades the light, for example by obstructing it, the detector assumes it is something like smoke and the alarm sounds. An ionization style of detector uses an ionization chamber and a small radioactive source to detect fast-burning fires. Shown in Figure 8.10, the chamber consists of two plates, one with a positive charge and one with a negative charge. Oxygen and nitrogen particles in the air become “ionized” (an ion is freed from the molecule). The freed ion, which has a negative charge, is attracted to the positive plate, and the remaining part of the molecule, now with a positive charge, is attracted to the negative plate. This movement of particles creates a very small electric current that the device measures. Smoke inhibits this process, and the detector will detect the resulting drop in current and sound an alarm. Both of these devices are often referred to generically as smoke detectors, and combinations of both varieties are possible. For more information on smoke detectors, see http://home.howstuffworks.com/home-improvement/household- safety/fire/smoke2.htm.

• Figure 8.10 An ionization chamber for an ionization type of smoke detector

Tech Tip

Testing Controls Because of the importance of their protection, safety controls should be periodically tested for proper operation and alerting. This should be a system-level, not device-level, test to ensure the entire control system performs in the intended manner.

Another type of fire detector is activated by heat. These devices also come in two varieties. Fixed-temperature or fixed-point devices activate if the temperature in the area ever exceeds some predefined level. Rate-of- rise or rate-of-increase temperature devices activate when there is a sudden increase in local temperature that may indicate the beginning stages of a fire. Rate-of-rise sensors can provide an earlier warning but are also responsible for more false warnings. A third type of detector is flame activated. This type of device relies on

the flames from the fire to provide a change in the infrared energy that can

be detected. Flame-activated devices are generally more expensive than the other two types but can frequently detect a fire sooner.

Power Protection Computer systems require clean electrical power, and for critical systems, uninterrupted power can be important as well. There are several elements used to manage the power to systems, including uninterruptible power supplies and backup power systems.

Tech Tip

UPS Attributes UPS systems have several attributes to consider:

The electrical load they can support (measured in kVA)

The length of time they can support the load The speed of providing power when there is a power failure

The physical space they occupy

UPS An uninterruptible power supply (UPS) is used to protect against short- duration power failures. There are two types of UPS, online and standby. An online UPS is in continuous use because the primary power source goes through it to the equipment. It uses AC line voltage to charge a bank of batteries. When the primary power source fails, an inverter in the UPS will change DC of the batteries into AC. A standby UPS has sensors to detect power failures. If there is a power failure, the load will be switched to the UPS. It stays inactive before a power failure, and takes more time than an online UPS to provide power when the primary source fails.

Backup Power and Cable Shielding Backup power sources, such as a motor generator, another electrical substation, and so on, are used to protect against a long-duration power failure. A voltage regulator and line conditioner are used to protect against unstable power supply and spikes. Proper grounding is essential for all electrical devices to protect against short circuits and static electricity. In more sensitive areas, cable shielding can be employed to avoid

interference. Power line monitoring can be used to detect changes in frequency and voltage amplitude, warning of brownouts or spikes. An emergency power off (EPO) switch can be installed to allow for the quick shutdown of power when required. To prevent electromagnetic interference and voltage spikes, electrical cables should be placed away from powerful electrical motors and lighting. Another source of power- induced interference can be fluorescent lighting, which can cause radio frequency interference.

Electromagnetic Interference Electromagnetic interference, or EMI, can plague any type of electronics, but the density of circuitry in the typical data center can make it a haven for EMI. EMI is defined as the disturbance on an electrical circuit caused by that circuit’s reception of electromagnetic radiation. Magnetic radiation enters the circuit by induction, where magnetic waves create a charge on the circuit. The amount of sensitivity to this magnetic field depends on a number of factors, including the length of the circuit, which can act like an antenna. EMI is grouped into two general types: narrowband and broadband. Narrowband EMI is, by its nature, electromagnetic energy with a small frequency band and, therefore, typically sourced from a device that is purposefully transmitting in the specified band. Broadband EMI covers a wider array of frequencies and is typically caused by some type of general electrical power use such as power lines or electric motors. In the United States, the Federal Communications Commission has

responsibility for regulating products that produce EMI and has developed a program for equipment manufacturers to adhere to standards for EMI immunity. Modern circuitry is designed to resist EMI. Cabling is a good example; the twist in unshielded twisted pair, or Category 6/6a, cable is there to reduce EMI. EMI is also controlled by metal computer cases that are grounded; by providing an easy path to ground, the case acts as an EMI shield. A bigger example would be a Faraday cage or Faraday shield, which is an enclosure of conductive material that is grounded. These can be room sized or built into a building’s construction; the critical element is that there is no significant gap in the enclosure material. These measures can help shield EMI, especially in high radio frequency environments. While we have talked about the shielding necessary to keep EMI

radiation out of your circuitry, there is also technology to try and help keep it in. Known by some as TEMPEST, it is also known as Van Eck emissions. A computer’s monitor or LCD display produces electromagnetic radiation that can be remotely observed with the correct equipment. TEMPEST was the code word for an NSA program to secure equipment from this type of eavesdropping. While some of the information about TEMPEST is still classified, there are guides on the Internet that describe protective measures, such as shielding and electromagnetic- resistant enclosures. A company has even developed a commercial paint that offers radio frequency shielding.

Tech Tip

Master Keys Mechanical keying systems with industrial-grade locks have provisions for multiple master keys. This allows individual master keys to be designated by floor, by department, by the whole building, and so forth. This provides tremendous flexibility, although if a master key is lost, significant rekeying will be required.

Electronic Access Control Systems Access tokens are defined as “something you have.” An access token is a physical object that identifies specific access rights. Access tokens are frequently used for physical access solutions, just as your house key is a basic physical access token that allows you access into your home. Although keys have been used to unlock devices for centuries, they do have several limitations. Keys are paired exclusively with a lock or a set of locks, and they are not easily changed. It is easy to add an authorized user by giving the user a copy of the key, but it is far more difficult to give that user selective access unless that specified area is already set up as a separate key. It is also difficult to take access away from a single key or key holder, which usually requires a rekey of the whole system. In many businesses, physical access authentication has moved to

contactless radio frequency cards and proximity readers. When passed near a card reader, the card sends out a code using radio waves. The reader picks up this code and transmits it to the control panel. The control panel checks the code against the reader from which it is being read and the type of access the card has in its database. One of the advantages of this kind of token-based system is that any card can be deleted from the system without affecting any other card or the rest of the system. The RFID-based contactless entry card shown in Figure 8.11 is a common form of this token device employed for door controls and is frequently put behind an employee badge. In addition, all doors connected to the system can be segmented in any form or fashion to create multiple access areas, with different permissions for each one. The tokens themselves can also be grouped in multiple ways to provide different access levels to different groups of people. All of the access levels or segmentation of doors can be modified quickly and easily if building space is retasked. Newer technologies are adding capabilities to the standard token-based systems.

• Figure 8.11 Smart cards have an internal chip as well as multiple external contacts for interfacing with a smart card reader.

The advent of smart cards (cards that contain integrated circuits capable of generating and storing cryptographic keys) has enabled cryptographic types of authentication. Smart card technology has proven reliable enough that it is now part of a governmental standard for physical and logical authentication. Known as Personal Identity Verification, or PIV, cards, they adhere to the FIPS 201 standard. This smart card includes a cryptographic chip and connector, as well as a contactless proximity card circuit. It also has standards for a printed photo and name printing on the front. Biometric data can be stored on the card, providing an additional authentication factor, and if the PIV standard is followed, several forms of

identification are needed to get a card.

Tech Tip

Personnel ID Badges Having personnel wear a visible ID badge with their picture is a common form of physical security. If everyone is supposed to wear a badge visibly, then anyone who sees someone without a badge can ask them who they are, and why they are there. This greatly increases the number of eyes watching for intruders in large, publicly accessible facilities.

The primary drawback of token-based authentication is that only the token is being authenticated. Therefore, the theft of the token could grant anyone who possessed the token access to what the system protects. The risk of theft of the token can be offset by the use of multiple-factor authentication. One of the ways that people have tried to achieve multiple- factor authentication is to add a biometric factor to the system.

Access Tokens Electronic access control systems were spawned from the need to have more logging and control than provided by the older method of metallic keys. Most electronic systems currently use a token-based card that if passed near a reader will unlock the door strike and let you pass into the area (assuming you have permission from the system). Newer technology attempts to make the authentication process easier and more secure. The following sections discuss how tokens and biometrics are being

used for authentication. It also looks into how multiple-factor authentication can be used for physical access.

Biometrics Biometrics use the measurements of certain biological factors to identify one specific person from others. These factors are based on parts of the

human body that are unique. The most well known of these unique biological factors is the fingerprint. Fingerprint readers have been available for several years in laptops. These come in a variety of form factors, such as the example shown in Figure 8.12, and as standalone USB devices.

• Figure 8.12 Newer laptop computers often include a fingerprint reader.

However, many other biological factors can be used, such as the retina or iris of the eye, the geometry of the hand, and the geometry of the face. When these are used for authentication, there is a two-part process: enrollment and then authentication. During enrollment, a computer takes the image of the biological factor and reduces it to a numeric value. When the user attempts to authenticate, their feature is scanned by the reader, and the computer compares the numeric value being read to the one stored in the database. If they match, access is allowed. Since these physical factors are unique, theoretically only the actual authorized person would be

allowed access. In the real world, however, the theory behind biometrics breaks down.

Tokens that have a digital code work very well because everything remains in the digital realm. A computer checks your code, such as 123, against the database; if the computer finds 123 and that number has access, the computer opens the door. Biometrics, however, take an analog signal, such as a fingerprint or a face, and attempt to digitize it, and it is then matched against the digits in the database. The problem with an analog signal is that it might not encode the exact same way twice. For example, if you came to work with a bandage on your chin, would the face-based biometrics grant you access or deny it? Engineers who designed these systems understood that if a system was

set to exact checking, an encoded biometric might never grant access since it might never scan the biometric exactly the same way twice. Therefore, most systems have tried to allow a certain amount of error in the scan, while not allowing too much. This leads to the concepts of false positives and false negatives. A false positive occurs when a biometric is scanned and allows access to someone who is not authorized—for example, two people who have very similar fingerprints might be recognized as the same person by the computer, which grants access to the wrong person. A false negative occurs when the system denies access to someone who is actually authorized—for example, a user at the hand geometry scanner forgot to wear a ring he usually wears and the computer doesn’t recognize his hand and denies him access. For biometric authentication to work properly, and also be trusted, it must minimize the existence of both false positives and false negatives. To do that, a balance between exacting and error must be created so that the machines allow a little physical variance—but not too much.

False Positives and False Negatives When a decision is made on information and an associated range of probabilities, the conditions exist for a false decision. Figure 8.13 illustrates two overlapping probabilities; an item belongs to either the red curve or the blue curve, but not both. The

problem in deciding which curve an item belongs to occurs when the curves overlap.

• Figure 8.13 Overlapping probabilities

When there is an overlapping area, it is typically referred to as the false positive and false negative rate. Note that in the accompanying figures, the size of overlap is greatly exaggerated to make it easy to see. Figure 8.14 illustrates a false positive detection. If the value observed is the dotted line, then it could be considered either a match or a non-match. If in fact it should not match, and the system tags it as a match, it is a false positive. In biometrics, a false positive would allow access to an unauthorized party.

• Figure 8.14 False positive

Figure 8.15 illustrates a false negative detection. If the value observed is the dotted line, then it could be considered either a match or a non-match. If in fact it should match, and the system tags it as a non-match, it is a false negative. A false negative would prevent an authorized user from obtaining access.

• Figure 8.15 False negative

Exam Tip: False positive and false negative are frequently confused. The true definitions revolve around the statistical term null hypothesis. For authentication, it is assumed that the person is not authorized. If the person is not authorized, and the test incorrectly rejects the null hypothesis and allows entry, this is a false positive—also called a Type I error. If the person is authorized, and the test fails to allow entry, then this is a false negative, or Type II error. The important element is the direction of the null hypothesis, which, for authentication, would be to deny entry.

To solve the false positive and false negative issue, the probabilistic engine must produce two sets of curves that do not overlap. This is equivalent to very low, <0.001%, false positive and false negative rates. Because the curves technically have tails that go forever, there will always be some false rates, but the numbers have to be exceedingly small to assure security. Figure 8.16 illustrates the desired, but typically impractical, separation of the curves.

• Figure 8.16 Desired situation

A more realistic situation has the two curves crossing over at some point, and this point is known as the crossover error rate (CER). The CER is the point where the false acceptance and false rejection rates are equal. While a system has the ability to adjust which of the two false rates to favor, the CER provides a means of comparing systems performance at discriminating signals. A system with a CER of 2 percent is more accurate (and has more separation) than one with a CER of 5 percent. Another concern with biometrics is that if someone is able to steal the

uniqueness factor that the machine scans—your fingerprint from a glass, for example—and is able to reproduce that factor in a substance that fools the scanner, that person now has your access privileges. This idea is compounded by the fact that it is impossible for you to change your fingerprint if it gets stolen. It is easy to replace a lost or stolen token and delete the missing one from the system, but it is far more difficult to replace a human hand. Another problem with biometrics is that parts of the human body can change. A human face can change, through scarring, weight loss or gain, or surgery. A fingerprint can be changed through damage to the fingers. Eye retinas can be affected by some types of diabetes or by pregnancy. All of these changes force the biometric system

to allow a higher tolerance for variance in the biometric being read. This has led the way for high-security installations to move toward multiple- factor authentication.

Multiple-Factor Authentication Multiple-factor authentication is simply the combination of two or more types of authentication. Three broad categories of authentication can be used: what you are (for example, biometrics), what you have (for instance, tokens), and what you know (passwords and other information). Two- factor authentication combines any two of these before granting access. An example would be a card reader that then turns on a fingerprint scanner—if your fingerprint matches the one on file for the card, you are granted access. Three-factor authentication would combine all three types, such as a smart card reader that asks for a PIN before enabling a retina scanner. If all three correspond to a valid user in the computer database, access is granted.

Exam Tip: Two-factor authentication combines any two methods of authentication, matching items such as a token with a biometric. Three-factor authentication combines any three, such as a passcode, biometric, and a token.

Multiple-factor authentication methods greatly enhance security by making it very difficult for an attacker to obtain all the correct materials for authentication. They also protect against the risk of stolen tokens, as the attacker must have the correct biometric, password, or both. More important, multiple-factor authentication enhances the security of biometric systems, by protecting against a stolen biometric. Changing the token makes the biometric useless unless the attacker can steal the new token. It also reduces false positives by trying to match the supplied biometric with the one that is associated with the supplied token. This prevents the computer from seeking a match using the entire database of

biometrics. Using multiple factors is one of the best ways to ensure proper authentication and access control.

Chapter 8 Review

Chapter Summary After reading this chapter and completing the exercises, you should understand the following facts about how physical security impacts network security.

Describe how physical security directly affects computer and network security

Physical access defeats all network security protections.

Bootdisks allow file system access.

Drive imaging is simple to accomplish with physical access.

Access to the internal network is simple with physical access.

Theft of hardware can be an attack in and of itself.

Discuss steps that can be taken to help mitigate risks

Removal of floppy drives and other media drives when they are unnecessary can help mitigate bootdisk attacks.

Removal of CD-ROM devices also makes physical access attacks more difficult.

BIOS passwords should be used to protect the boot sequence.

USB devices are a threat and thus, if possible, USB drivers should be removed.

All users need security training.

Authentication systems should use multiple factors when feasible.

Identify the different types of fires and the various fire suppression systems designed to limit the damage caused by fires

Fires can be caused by and can consume a number of different materials. It is important to recognize what type of fire is occurring, because the extinguisher to use depends on the type of fire.

The ABC fire extinguisher is the most common type and is designed to handle most types of fires. The only type of fire it is not designed to address is one with combustible metals.

Explain electronic access controls and the principles of convergence

Access controls should have layered areas and electronic access control systems.

Electronic physical security systems need to be protected from network-based attacks.

Key Terms access tokens (210) autoplay (201) biometrics (211) BIOS passwords (200) bootdisk (192) closed circuit television (CCTV) (198) contactless access cards (197) convergence (200) crossover error rate (CER) (214) drive imaging (194) false negative (212)

false positive (212) layered access (197) LiveCD (193) mantrap (198) multiple-factor authentication (214) physical access control (196) policies and procedures (200) smart cards (211) Unified Extensible Firmware Interface (UEFI) (200) USB devices (201)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. A door system designed to only allow a single person through is called a(n) _______________.

2. _______________ include MP3 players and flash drives. 3. A(n) _______________ happens when an unauthorized user is

allowed access.

4. Removable media from which a computer can be booted is called a(n) _______________.

5. _______________ forces a user to authenticate again when entering a more secure area.

6. Items carried by the user to allow them to be authenticated are called _______________.

7. _______________ is the measurement of unique biological properties, like the fingerprint.

8. _______________ prevent an attacker from making the machine boot off the DVD drive.

9. _______________ is a system where the camera and monitor are directly linked.

10. Using a token, fingerprint reader, and PIN keypad would be an example of _______________.

Multiple-Choice Quiz 1. What is the most common example of an access token?

A. Smart card

B. Handwriting sample

C. PDA

D. Key

2. Which one is not commonly used as a biometric? A. Eye retina

B. Hand geometry

C. Shoulder-to-waist geometry

D. Fingerprint

3. Probably the simplest physical attack on the computer system is: A. Accessing an Ethernet jack to attack the network

B. Using an imitation to fool a biometric authenticator

C. Installing a virus on the CCTV system

D. Outright theft of the computers

4. What is a common threat to token-based access controls?

A. The key

B. Demagnetization of the strip

C. A system crash

D. Loss or theft of the token

5. Why can USB flash drives be a threat? A. They use too much power.

B. They can bring malicious code past other security mechanisms.

C. They can be stolen.

D. They can be encrypted.

6. Why is HVAC important to computer security? A. Sabotage of the AC unit could take out the electrical power.

B. Sabotage of the AC unit would make the computers overheat and shut down.

C. The AC units could be connected to the network.

D. HVAC is not important to security.

7. Why should security guards get cross-training in network security? A. They are the eyes and ears of the corporation when it comes to

security.

B. They are the only people in the building at night.

C. They are more qualified to know what a security threat is.

D. They have the authority to detain violators.

8. Why is enrollment important to biometrics? A. Fingerprints are unique.

B. It adds another layer to the layered access model.

C. If enrollment is not done carefully, false positives will increase.

D. It completely prevents false positives.

9. Why is physical security so important to good network security? A. Because encryption is not involved

B. Because physical access defeats nearly all network security measures

C. Because an attacker can steal biometric identities

D. Authentication

10. How does multiple-factor authentication improve security? A. By using biometrics, no other person can authenticate.

B. It restricts users to smaller spaces.

C. By using a combination of authentications, it is more difficult for someone to gain illegitimate access.

D. It denies access to an intruder multiple times.

Essay Questions 1. You have been asked to report on the feasibility of installing an IP

CCTV camera system at your organization. Detail the pros and cons of an IP CCTV system and how you would implement the system.

2. Write a memo justifying layered access for devices in an organization.

3. Write a memo justifying more user education about physical security.

4. Write a sample policy regarding the use of USB devices in an

organization.

Lab Projects

• Lab Project 8.1 Load a LiveCD on your machine and examine the tools it provides. You will need the following materials:

A computer with a version of Windows installed and a CD/DVD burner

An empty CD or DVD Then do the following:

1. Download a copy of Kali Linux. A good site from which to obtain this is www.kali.org/downloads/.

2. Burn the ISO file to the CD/DVD.

3. Reboot the machine, allowing the LiveCD to start the machine in Linux. 4. Once Kali Linux is running, open a terminal window and type wireshark.

5. With Wireshark open as a sniffing program, record the traffic to and from this computer. A. Open Capture | Options.

B. Select Start on your Ethernet interface, usually eth0.

C. Stop Capture by selecting Capture | Stop.

D. Click any packet listed to view the analysis.

6. View the other tools on the CD under KDE | Kali.

• Lab Project 8.2 Disable autoplay on your system for several types of media. You will need the following materials:

A computer with Windows A USB flash drive that is set to be bootable

A CD/DVD with an autoplay file

Then do the following:

1. Insert the CD/DVD and verify that autoplay is on and working.

2. Follow this chapter’s instructions on disabling autoplay. 3. Reinsert the CD/DVD and verify that autoplay is disabled—nothing should appear when

the CD/DVD is inserted now.

4. Insert the USB flash drive and see if autoplay works for it; if it does, disable it using the same method.

chapter 9 Network Fundamentals

The value of a communications network is proportional to the square of the number of its users.

—METCALFE’S LAW

B

In this chapter, you will learn how to

Identify the basic network architectures

Define the basic network protocols

Explain routing and address translation

Classify security zones

y the simplest definition in the data world, a network is a means to connect two or more computers together for the purposes of sharing information. The term “network” has different meanings depending on

the context and usage. A network can be a group of friends and associates, a series of interconnected tunnels, or, from a computer-oriented perspective, a collection of interconnected devices. Network sizes and shapes vary drastically, ranging from two personal computers connected with a crossover cable or wireless router all the way up to the Internet, encircling the globe and linking together untold numbers of individual, distributed systems. Though data networks vary widely in size and scope, they are generally defined in terms of their architecture, topology, and protocols.

Network Architectures Every network has an architecture—whether by design or by accident. Defining or describing a specific network’s architecture involves identifying the network’s physical configuration, logical operation, structure, procedures, data formats, protocols, and other components. For the sake of simplicity and categorization, people tend to divide network architectures into two main categories: LANs and WANs. A local area network (LAN) typically is smaller in terms of size and geographic coverage and consists of two or more connected devices. Home networks and most small office networks can be classified as LANs. A wide area

network (WAN) tends to be larger, covering more geographic area, and consists of two or more systems in geographically separated areas connected by any of a variety of methods such as leased lines, radio waves, satellite relays, microwaves, or even dial-up connections. With the advent of wireless networking, optical, and cellular technology, the lines between LAN and WAN sometimes seem to merge seamlessly into a single network entity. For example, most corporations have multiple LANs within each office location that all connect to a WAN that provides intercompany connectivity. Figure 9.1 shows an example of a corporate network. Each office location will typically have one or more LANs, which are connected to the other offices and the company headquarters through a corporate WAN.

• Figure 9.1 Corporate WAN connecting multiple offices

Exam Tip: A LAN is a local area network—an office building, home network, and so on. A WAN is a wide area network—a corporate network connecting offices in Dallas, New York, and San Jose, for example.

Over time, as networks have grown, diversified, and multiplied, the line between LAN and WAN has become blurred. To better describe emerging, specialized network structures, new terms have been coined to classify networks based on size and use:

Campus area network (CAN) A network connecting any number of buildings in an office or university complex (also referred to as a campus wide area network).

Intranet A “private” network that is accessible only to authorized users. Many large corporations host an intranet to facilitate information sharing within their organization.

Internet The “global network” connecting hundreds of millions of systems and users.

Metropolitan area network (MAN) A network designed for a specific geographic locality such as a town or a city.

Storage area network (SAN) A high-speed network connecting a variety of storage devices such as tape systems, RAID arrays, optical drives, file servers, and others.

Virtual local area network (VLAN) A logical network allowing systems on different physical networks to interact as if they were connected to the same physical network.

Client/server A network in which powerful, dedicated systems called servers provide resources to individual workstations or clients.

Peer-to-peer A network in which every system is treated as an equal, such as a home network.

Network Topology One major component of every network’s architecture is the network’s topology—how the network is physically or logically arranged. Terms to classify a network’s topology have been developed, often reflecting the physical layout of the network. The main classes of network topologies are star, ring, bus, and mixed.

Star topology Network components are connected to a central point. (See Figure 9.2.)

• Figure 9.2 Star topology

Bus topology Network components are connected to the same cable, often called “the bus” or “the backbone.” (See Figure 9.3.)

• Figure 9.3 Bus topology

Ring topology Network components are connected to each other in a closed loop with each device directly connected to two other devices. (See Figure 9.4.)

• Figure 9.4 Ring topology

Larger networks, such as those inside an office complex, may use more than one topology at the same time. For example, an office complex may have a large ring topology that interconnects all the buildings in the complex. Each building may have a large bus topology to interconnect star topologies located on each floor of the building. This is called a mixed topology or hybrid topology. (See Figure 9.5.)

• Figure 9.5 Mixed topology

With recent advances in technology, these topology definitions often break down. While a network consisting of five computers connected to the same coaxial cable is easily classified as a bus topology, what about those same computers connected to a switch using Cat-5 cables? With a switch, each computer is connected to a central node, much like a star topology, but the backplane of the switch is essentially a shared medium.

With a switch, each computer has its own exclusive connection to the switch like a star topology, but has to share the switch’s communications backbone with all the other computers, much like a bus topology. To avoid this type of confusion, many people use topology definitions only to identify the physical layout of the network, focusing on how the devices are connected to the network. If we apply this line of thinking to our example, the five-computer network becomes a star topology whether we use a hub or a switch.

Wireless networks use radio waves as their medium to transmit packets, and those radio waves don’t stop at the walls of your house or your organization. Anyone within range can “see” those radio waves and attempt to either sniff your traffic or connect to your network. Encryption, MAC address filtering, and suppression of beacon frames are all security mechanisms to consider when using wireless networks. Wireless networks, because of the signal propagation, can easily assume a mesh structure.

Network Protocols How do all these interconnected devices communicate? What makes a PC in China able to view web pages on a server in Brazil? When engineers first started to connect computers together via networks, they quickly realized they needed a commonly accepted method for communicating—a protocol.

Protocols A protocol is an agreed-upon format for exchanging or transmitting data between systems. A protocol defines a number of agreed-upon parameters, such as the data compression method, the type of error checking to use, and mechanisms for systems to signal when they have finished either receiving or transmitting data. There is a wide variety of protocols, each

designed with certain benefits and uses in mind. Some of the more common protocols that have been used in networking are listed next. Today, most networks are dominated by Ethernet and Internet Protocol.

AppleTalk The communications protocol developed by Apple to connect Macintosh computers and printers.

Asynchronous Transfer Mode (ATM) A protocol based on transferring data in fixed-size packets. The fixed packet sizes help ensure that no single data type monopolizes the available bandwidth.

Ethernet The LAN protocol developed jointly by Xerox, DEC, and Intel—the most widely implemented LAN standard.

Fiber Distributed Data Interface (FDDI) The protocol for sending digital data over fiber-optic cabling.

Internet Protocols (IP) The protocols for managing and transmitting data between packet-switched computer networks, originally developed for the Department of Defense. Most users are familiar with Internet protocols such as e-mail, File Transfer Protocol (FTP), Telnet, and Hypertext Transfer Protocol (HTTP).

Internetwork Packet Exchange (IPX) The networking protocol created by Novell for use with Novell NetWare operating systems.

Signaling System 7 (SS7) The telecommunications protocol used between private branch exchanges (PBXs) to handle tasks such as call setup, routing, and teardown.

Systems Network Architecture (SNA) A set of network protocols developed by IBM, originally used to connect IBM’s mainframe systems.

Token Ring A LAN protocol developed by IBM that requires systems to possess the network “token” before transmitting data.

Transmission Control Protocol/Internet Protocol (TCP/IP) The collection of communications protocols used to connect hosts on the

Internet. TCP/IP is by far the most commonly used network protocol and is a combination of the TCP and IP protocols.

X.25A protocol Developed by the Comité Consultatif International Téléphonique et Télégraphique (CCITT) for use in packet-switched networks. The CCITT was a subgroup within the International Telecommunication Union (ITU) before the CCITT was disbanded in 1992.

A little history on the IP protocol from Wikipedia: “In May, 1974, the Institute of Electrical and Electronic Engineers (IEEE) published a paper entitled ‘A Protocol for Packet Network Interconnection.’ The paper’s authors, Vint Cerf and Bob Kahn, described an internetworking protocol for sharing resources using packet-switching among the nodes.”

In most cases, communications protocols were developed around the Open System Interconnection (OSI) model. The OSI model, or OSI Reference Model, is an International Organization for Standardization (ISO) standard for worldwide communications that defines a framework for implementing protocols and networking components in seven distinct layers. Within the OSI model, control is passed from one layer to another (top-down) before it exits one system and enters another system, where control is passed bottom-up to complete the communications cycle. It is important to note that most protocols only loosely follow the OSI model; several protocols combine one or more layers into a single function. The OSI model also provides a certain level of abstraction and isolation for each layer, which only needs to know how to interact with the layer above and below it. The application layer, for example, only needs to know how to communicate with the presentation layer—it does not need to talk directly to the physical layer. Figure 9.6 shows the different layers of the OSI model.

• Figure 9.6 The OSI Reference Model

Packets Networks are built to share information and resources, but like other forms of communication, networks and the protocols they use have limits and rules that must be followed for effective communication. For example, large chunks of data must typically be broken up into smaller, more manageable chunks before they are transmitted from one computer to another. Breaking the data up has advantages—you can more effectively share bandwidth with other systems and you don’t have to retransmit the entire dataset if there is a problem in transmission. When data is broken up into smaller pieces for transmission, each of the smaller pieces is typically called a packet. Each protocol has its own definition of a packet—

dictating how much data can be carried, what information is stored where, how the packet should be interpreted by another system, and so on.

The concept of breaking a message into pieces before sending it is as old as networking. The terms used to describe these pieces can vary from protocol to protocol. Frame Relay and Ethernet both use the term frame. ATM calls them cells. Many protocols use the generic term packet. In the OSI model, the term datagram is used. At the end of the day, regardless of what it is called, these pieces are protocol-defined, formatted structures used to carry information.

A standard packet structure is a crucial element in a protocol definition. Without a standard packet structure, systems would not be able to interpret the information coming to them from other systems. Packet-based communication systems have other unique characteristics, such as size, which need to be addressed. This is done via a defined maximum and fragmenting packets that are too big, as shown in the next sections.

Maximum Transmission Unit When transmitting packets across a network, there are many intervening protocols and pieces of equipment, each with its own set of limitations. One of the factors used to determine how many packets a message must be broken into is the Maximum Transmission Unit (MTU). The MTU is the largest packet that can be carried across a network channel. The value of the MTU is used by TCP to prevent packet fragmentation at intervening devices. Packet fragmentation is the splitting of a packet while in transit into two packets so that they fit past an MTU bottleneck.

Packet Fragmentation Built into the Internet Protocol is a mechanism for handling of packets that are larger than allowed across a hop. Under ICMP v4, a router has two options when it encounters a packet that is too large for the next hop: break the packet into two fragments, sending each separately, or drop the packet

and send an ICMP message back to the originator, indicating that the packet is too big. When a fragmented packet arrives at the receiving host, it must be reunited with the other packet fragments and reassembled. One of the problems with fragmentation is that it can cause excessive levels of packet retransmission as TCP must retransmit an entire packet for the loss of a single fragment. In IPv6, to avoid fragmentation, hosts are required to determine the minimal path MTU before transmission of packets to avoid fragmentation en route. Any fragmentation requirements in IPv6 are resolved at the origin, and if fragmentation is required, it occurs before sending.

Tech Tip

IPv6 and Fragmentation IPv6 systems calculate the MTU and then adhere to that from host to host. This prevents fragmentation en route; instead all fragmentation is done by the originating host to fit under the MTU limit.

IP fragmentation can be exploited in a variety of ways to bypass security measures. Packets can be purposefully constructed to split exploit code into multiple fragments to avoid IDS detection. Because the reassembly of fragments is dependent upon data in the fragments, it is possible to manipulate the fragments to result in datagrams that exceed the 64KB limit, resulting in denial of service.

Internet Protocol The Internet Protocol is not a single protocol but a suite of protocols. The relationship between some of the IP suite and the OSI model is shown in Figure 9.7. As you can see, there are differences between the two versions of the protocol in use, v4 and v6. The protocol elements and their security implications are covered in the next sections of this chapter. One of these

differences is the replacement of the Internet Group Management Protocol (IGMP) with the Internet Control Message Protocol (ICMP) and Multicast Listener Discovery (MLD) in IPv6.

• Figure 9.7 Internet Protocol suite components

IP Packets To better understand packet structure, let’s examine the packet structure defined by the IP protocol. An IP packet, often called a datagram, has two main sections: the header and the data section (sometimes called the payload). The header section contains all of the information needed to describe the packet (see Figure 9.8).

• Figure 9.8 Logical layout of an IP packet, (a) IPv4 (b) IPv6

In IPv4, there are common fields to describe the following options.

What kind of packet it is (protocol version number)

How large the header of the packet is (packet header length)

How to process this packet (type of service telling the network whether or not to use options such as minimize delay, maximize throughput, maximize reliability, and minimize cost)

How large the entire packet is (overall length of packet—since this is a 16-bit field, the maximum size of an IP packet is 65,535 bytes, but in practice most packets are around 1500 bytes)

A unique identifier so that this packet can be distinguished from other packets

Whether or not this packet is part of a longer data stream and should be handled relative to other packets

Flags that indicate whether or not special handling of this packet is necessary

A description of where this packet fits into the data stream as compared to other packets (the fragment offset)

A “time to live” field that indicates the packet should be discarded if the value is zero

A protocol field that describes the encapsulated protocol

A checksum of the packet header (to minimize the potential for data corruption during transmission)

Where the packet is from (source IP address, such as 10.10.10.5)

Where the packet is going (destination IP address, such as 10.10.10.10)

Option flags that govern security and handling restrictions, whether or not to record the route this packet has taken, whether or not to record time stamps, and so on

The data this packet carries

In IPv6, the source and destination addresses take up much greater

room, and for equipment and packet handling reasons, most of the informational options have been moved to the optional area after the addresses. This series of optional extension headers allows the efficient use of the header in processing the routing information during packet routing operations. One of the most common options is the IPsec extension, which is used

to establish IPsec connections. IPsec uses encryption to provide a variety of protections to packets. IPsec is fully covered in Chapter 11.

Tech Tip

The Importance of Understanding TCP/IP Protocols A security professional must understand how the various TCP/IP protocols operate. For example, if you’re looking at a packet capture of a suspected port scan, you need to know how “normal” TCP and UDP traffic works so you will be able to spot “abnormal” traffic. This chapter provides a very basic overview of the most popular protocols: TCP, UDP, and ICMP.

As you can see, this standard packet definition allows systems to communicate. Without this type of “common language,” the global connectivity we enjoy today would be impossible—the IP protocol is the primary means for transmitting information across the Internet.

TCP vs. UDP Protocols are typically developed to enable a certain type of communication or solve a specific problem. Over the years, this approach has led to the development of many different protocols, each critical to the function or process it supports. However, there are two protocols that have grown so much in popularity and use that without them, the Internet as we know it would cease to exist. These two protocols, the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), are protocols that run on top of the IP network protocol. As separate protocols,

they each have their own packet definitions, capabilities, and advantages, but the most important difference between TCP and UDP is the concept of “guaranteed” reliability and delivery.

Exam Tip: TCP is a “connection-oriented” protocol and offers reliability and guaranteed delivery of packets. UDP is a “connectionless” protocol with no guarantees of delivery.

UDP is known as a “connectionless” protocol as it has very few error- recovery services and no guarantee of packet delivery. With UDP, packets are created and sent on their way. The sender has no idea whether the packets were successfully received or whether they were received in order. In that respect, UDP packets are much like postcards—you address them and drop them in the mailbox, not really knowing if, when, or how the postcards reach your intended audience. Even though packet loss and corruption are relatively rare on modern networks, UDP is considered to be an unreliable protocol and is often only used for network services that are not greatly affected by the occasional lost or dropped packet. Time synchronization requests, name lookups, and streaming audio are good examples of network services based on UDP. UDP also happens to be a fairly “efficient” protocol in terms of content delivery versus overhead. With UDP, more time and space is dedicated to content (data) delivery than with other protocols such as TCP. This makes UDP a good candidate for streaming protocols, as more of the available bandwidth and resources are used for data delivery than with other protocols. TCP is a “connection-oriented” protocol and was specifically designed

to provide a reliable connection between two hosts exchanging data. TCP was also designed to ensure that packets are processed in the same order in which they were sent. As part of TCP, each packet has a sequence number to show where that packet fits into the overall conversation. With the sequence numbers, packets can arrive in any order and at different times and the receiving system will still know the correct order for processing

them. The sequence numbers also let the receiving system know if packets are missing—receiving packets 1, 2, 4, and 7 tells us that packets 3, 5, and 6 are missing and needed as part of this conversation. The receiving system can then request retransmission of packets from the sender to fill in any gaps. The “guaranteed and reliable” aspect of TCP makes it very popular for

many network applications and services such as HTTP, FTP, and Telnet. As part of the connection, TCP requires that systems follow a specific pattern when establishing communications. This pattern, often called the three-way handshake (shown in Figure 9.9), is a sequence of very specific steps:

• Figure 9.9 TCP’s three-way handshake

1. The originating host (usually called the client) sends a SYN (synchronize) packet to the destination host (usually called the server). The SYN packet tells the server what port the client wants to connect to and the initial packet sequence number of the client.

2. The server sends a SYN/ACK packet back to the client. This SYN/ACK (synchronize/acknowledge) tells the client “I received your request” and also contains the server’s initial packet sequence number.

3. The client responds to the server with an ACK packet to complete the connection establishment process.

Think of the three-way handshake as being similar to a phone call. You place a call to your friend —that’s the SYN. Your friend answers the phone and says “hello”—that’s the SYN/ACK. Then you say “Hi, it’s me”—that’s the ACK. Your connection is established and you can start your conversation.

ICMP While TCP and UDP are arguably the most common protocols, the Internet Control Message Protocol (ICMP) is probably the third most commonly used protocol. During the early development of large networks, it was quickly discovered that there needed to be some mechanism for managing the overall infrastructure—handling connection status, traffic flow, availability, and errors. This mechanism is ICMP. ICMP is a control and information protocol and is used by network devices to determine such things as a remote network’s availability, the length of time to reach a remote network, and the best route for packets to take when traveling to that remote network (using ICMP redirect messages, for example). ICMP can also be used to handle the flow of traffic, telling other network devices to “slow down” transmission speeds if packets are coming in too fast.

Tech Tip

TCP Packet Flags TCP packets contain flags—dedicated fields that are used to help the TCP protocol control and manage the TCP session. There are eight different flags in a TCP packet, and when a flag is “set,” it is set to a value of 1. The eight different flags are

CWR (Congestion Window Reduced) Set by a host to indicate that it received a packet with the ECE flag set and is taking action to help reduce congestion.

ECE (ECN-Echo) Indicates that the TCP peer is ECN capable when used during the three-way handshake. During normal traffic, this flag means that a packet with a Congestion Experienced flag in its IP header was received by the host sending this

packet.

URG (Urgent) When set, the urgent pointer in the packets should be read as valid and followed for additional data.

ACK (Acknowledgment) Indicates that the data in the ACK field should be processed.

PSH (Push) Indicates that data delivery should start immediately rather than waiting for buffers to fill up first.

RST (Reset) Resets the current connection—a start-over feature often used by IPS/IDS devices to interrupt sessions.

SYN (Synchronize) Used to help synchronize sequence numbers. FIN (Finish) Indicates the sender is finished and has no more data to send.

ICMP, like UDP, is a connectionless protocol. ICMP was designed to carry small messages quickly with minimal overhead or impact to bandwidth. ICMP packets are sent using the same header structure as IP packets, with the protocol field set to 1 to indicate that it is an ICMP packet. ICMP packets also have their own header, which follows the IP header and contains type, code, checksum, sequence number, identifier, and data fields. The “type” field indicates what type of ICMP message it is, and the “code” field tells us what the message really means. For example, an ICMP packet with a type of 3 and a code of 2 would tell us this is a “destination unreachable” message and, more specifically, a “host unreachable” message—usually indicating that we are unable to communicate with the intended destination. Because ICMP messages in IPv6 can use IPsec, ICMP v6 messages can have significant protections from alteration. Unfortunately, ICMP has been greatly abused by attackers over the last

few years to execute denial-of-service (DoS) attacks. Because ICMP packets are very small and connectionless, thousands and thousands of ICMP packets can be generated by a single system in a very short period of time. Attackers have developed methods to trick many systems into generating thousands of ICMP packets with a common destination—the attacker’s target. This creates a literal flood of traffic that the target, and in most cases the network the target sits on, is incapable of dealing with. The

ICMP flood drowns out any other legitimate traffic and prevents the target from accomplishing its normal duties—denying access to the service the target normally provides. This has led to many organizations blocking all external ICMP traffic at the perimeter of their organization.

Tech Tip

ICMP Message Codes With ICMP packets, the real message of the packet is contained in the “type and code” fields, not the data field. Following are some of the more commonly seen ICMP type codes. Note that ICMP v6 has broken the listing into two types: error messages (0—127) and informational messages (128—255, presented in the latter half of the table). IPv6 introduces many new protocols, two of which will have significant implications: the Neighbor Discovery Protocol (NDP), which manages the interactions between neighboring IPv6 nodes, and Multicast Listener Discovery (MLD), which manages IPv6 multicast groups.

Tech Tip

Many of the messages have associated code values that make the message more specific. For

example, ICMP v4 messages with a type of 3 can have any of the following codes:

Cross Check Ping Sweep In Chapter 1 you learned about a “ping sweep.” What is a ping sweep and what is it used for? What types of ICMP packets could you use to conduct a ping sweep? How does this differ between ICMP v4 and ICMP v6?

Tech Tip

Should You Block ICMP? ICMP is a protocol used for troubleshooting, error reporting, and a wide variety of associated functionality. This functionality expands in ICMP v6 into multicasting. ICMP got a bad name primarily because of issues associated with ping and traceroute commands, but these represent a tiny minority of the protocol functionality. There are numerous important uses associated with ICMP, and blocking it in its entirety is a bad practice. Blocking specific commands and specific sources makes sense; blanket blocking is a poor practice that will lead to network inefficiencies. Blocking ICMP v6 in its entirety will block a lot of IPv6 functionality because ICMP is now an integral part of the protocol suite.

IPv4 vs. IPv6 The most common version of IP in use is IPv4, but the release of IPv6, spurred by the depletion of the IPv4 address space, has begun a typical logarithmic adoption curve. IPv6 has many similarities to the previous version, but it also has significant new enhancements, many of which have significant security implications.

Expanded Address Space The expansion of the address space from 32 bits to 128 bits is a significant change. Where IPv4 did not have enough addresses for each person on earth, IPv6 has over 1500 addresses per square meter of the entire earth’s surface. This has one immediate implication: where you could use a scanner to search all addresses for responses in IPv4, doing the same in IPv6 will take significantly longer. A one millisecond scan in IPv4 equates to a 2.5 billion year scan in IPv6. In theory, the 128 bits of IPv6 address space will express 3.4 × 1038 possible nodes. The IPv6 addressing protocol has been designed to allow for a hierarchal division of the address space into several layers of subnets, to assist in the maintaining of both efficient and logical address allocations. One example is the embedding of the IPv4

address space in the IPv6 space. This also has an intentional effect of simplifying the backbone routing infrastructures by reducing the routing table size.

Tech Tip

IPv6 Top Security Concerns There are numerous IPv6 security concerns, some technical, some operational. Some of the top security concerns are

Lack of IPv6 security training/education.

Security device bypass via IPv6. Poor IPv6 security policies.

Address notation makes grepping through logs difficult if not impossible. IPv6 complexity increases operational challenges for correct deployment.

Network Discovery IPv6 introduces the Network Discovery (NDP) protocol, which is useful for auto-configuration of networks. NDP can enable a variety of interception and interruption threat modes. A malevolent router can attach itself to a network and reroute or interrupt traffic flows.

Benefits of IPv6 Change is always a difficult task, and when the change will touch virtually everything in your system, this makes it even more difficult. Changing from IPv4 to IPv6 is not a simple task, for it will have an effect on every networked resource. The good news is that this is not a sudden or surprise process; vendors have been making products IPv6 capable for almost a decade. By this point, virtually all the network equipment you rely upon will be dual-stack capable, meaning that they can operate in both IPv4 and IPv6 networks. This provides a method for an orderly transfer from IPv4

to IPv6. IPv6 has many useful benefits and ultimately will be more secure

because it has many security features built into the base protocol series. IPv6 has a simplified packet header and new addressing scheme. This can lead to more efficient routing through smaller routing tables and faster packet processing. IPv6 was designed to incorporate multicasting flows natively, which allows bandwidth-intensive multimedia streams to be sent simultaneously to multiple destinations. IPv6 has a host of new services, from auto-configuration to mobile device addressing, and service enhancements to improve the robustness of QoS and VoIP functions. The security model of IPv6 is baked into the protocol, and is

significantly enhanced from the nonexistent one in IPv4. IPv6 is designed to be secure from sender to receiver, with IPsec available natively across the protocol. This will significantly improve communication level security, but it has also drawn a lot of attention. The use of IPsec will change the way security functions are performed across the enterprise. Old IPv4 methods, such as NAT and packet inspection methods of IDS, will need to be adjusted to the new model. Security appliances will have to adapt to the new protocol and its enhanced nature.

Packet Delivery Protocols are designed to help information get from one place to another, but in order to deliver a packet we have to know where it is going. Packet delivery can be divided into two sections: local and remote. Ethernet is common for local delivery, while IP works for remote delivery. Local packet delivery applies to packets being sent out on a local network, while remote packet delivery applies to packets being delivered to a remote system, such as across the Internet. Ultimately, packets may follow a local delivery–remote delivery–local delivery pattern before reaching their intended destination. The biggest difference in local versus remote delivery is how packets are addressed. Network systems have addresses, not unlike office numbers or street addresses, and before a packet can be

successfully delivered, the sender needs to know the address of the destination system.

Tech Tip

MAC Addresses Every network device should have a unique MAC address. Manufacturers of network cards and network chipsets have blocks of MAC addresses assigned to them, so you can often tell what type of equipment is sending packets by looking at the first three pairs of hexadecimal digits in a MAC address. For example “00-00-0C” would indicate the network device was built by Cisco Systems.

Ethernet Ethernet is the most widely implemented Layer 2 protocol. Ethernet is standardized under IEEE 802.3. Ethernet works by forwarding packets on a hop-to-hop basis using MAC addresses. Layer 2 addressing can have numerous security implications. Layer 2 addresses can be poisoned, spanning tree algorithms can be attacked, VLANs can be hopped, and more. Because of its near ubiquity, Ethernet is a common attack vector. It has many elements that make it useful from a networking point of view, such as its broadcast nature and its ability to run over a wide range of media. But these can also act against security concerns. Wireless connections are frequently considered to be weak from a security point of view, but so should Ethernet, for unless you own the network, you should consider the network to be at risk.

Local Packet Delivery Packets delivered on a network, such as an office LAN, are usually sent using the destination system’s hardware address, or Media Access Control (MAC) address. Each network card or network device is

supposed to have a unique hardware address so that it can be specifically addressed for network traffic. MAC addresses are assigned to a device or network card by the manufacturer, and each manufacturer is assigned a specific block of MAC addresses to prevent two devices from sharing the same MAC address. MAC addresses are usually expressed as six pairs of hexadecimal digits, such as 00:07:e9:7c:c8:aa. In order for a system to send data to another system on the network, it must first find out the destination system’s MAC address.

Try This! Finding MAC Addresses on Windows Systems Open a command prompt on a Windows system. Type the command ipconfig /all and find your system’s MAC address. Hint: It should be listed under “Physical Address” on your network adapters. Now type the command arp –a and press ENTER. What information does this display? Can you find the MAC address of your default gateway?

Maintaining a list of every local system’s MAC address is both costly and time consuming, and although a system may store MAC addresses temporarily for convenience, in many cases the sender must find the destination MAC address before sending any packets. To find another system’s MAC address, the Address Resolution Protocol (ARP) is used. Essentially, this is the computer’s way of finding out “who owns the blue convertible with license number 123JAK.” In most cases, systems know the IP address they wish to send to, but not the MAC address. Using an ARP request, the sending system will send out a query: Who is 10.1.1.140? This broadcast query is examined by every system on the local network, but only the system whose IP address is 10.1.1.140 will respond. That system will send back a response that says “I’m 10.1.1.140 and my MAC address is 00:07:e9:7c:c8:aa.” The sending system will then format the packet for delivery and drop it on the network media, stamped with the MAC address of the destination workstation.

MAC addresses can be “spoofed” or faked. Some operating systems allow users with administrator-level privileges to explicitly set the MAC address for their network card(s). For example, in Linux operating systems you can use the ifconfig command to change a network adapter’s MAC address. The command ifconfig eth0 hw ether 00:07:e9:7c:c8:aa will set the MAC address of adapter eth0 to 00:07:e9:7c:c8:aa. There are also a number of software utilities that allow you to do this through a GUI, such as the GNU MAC Changer. GUI utilities to change MAC addresses on Windows systems are also available.

Cross Check Mandatory Access Control vs. Media Access Control In Chapter 2 you learned about a different MAC—mandatory access control. What is the difference between mandatory access control and Media Access Control? What is each used for? When using acronyms it can be critical to ensure all parties are aware of the context of their usage.

ARP Attacks ARP operates in a simplistic and efficient manner—a broadcast request followed by a unicast reply. This method leaves ARP open to attack, which in turn can result in losses of integrity, confidentiality, and availability. Because ARP serves to establish communication channels, failures at this level can lead to significant system compromises. There is a wide range of ARP-specific attacks, but one can classify them into types based on effect.

Tech Tip

Rogue Device Detection There is always a risk of a rogue (unauthorized) device being inserted into the network. To detect when this happens, maintaining a list of all authorized MAC addresses can help detect these devices. Although MACs can be copied and spoofed, this would also set up a conflict if

the original device was present. Monitoring for these conditions can detect the insertion of a rogue device.

ARP can be a vector employed to achieve a man-in-the-middle attack. There are many specific ways to create false entries in a machine’s ARP cache, but the effect is the same: communications will be routed to an attacker. This type of attack is called ARP poisoning. The attacker can use this method to inject himself into the middle of a communication, hijack a session, sniff traffic to obtain passwords or other sensitive items, or block the flow of data, creating a denial of service. Although ARP is not secure, all is not lost with many ARP-based

attacks. Higher-level packet protections such as IPsec can be employed so that the packets are unreadable by interlopers. This is one of the security gains associated with IPv6, because when security is employed at the IPsec level, packets are protected below the IP level, making Layer 2 attacks less successful.

Remote Packet Delivery While packet delivery on a LAN is usually accomplished with MAC addresses, packet delivery to a distant system is usually accomplished using Internet Protocol (IP) addresses. IP addresses are 32-bit numbers that usually are expressed as a group of four numbers (such as 10.1.1.132). In order to send a packet to a specific system on the other side of the world, you have to know the remote system’s IP address. Storing large numbers of IP addresses on every PC is far too costly, and most humans are not good at remembering collections of numbers. However, humans are good at remembering names, so the Domain Name System (DNS) protocol was created.

DNS DNS translates names into IP addresses. When you enter the name of your favorite web site into the location bar of your web browser and press

ENTER, the computer has to figure out what IP address belongs to that name. Your computer takes the entered name and sends a query to a local DNS server. Essentially, your computer asks the DNS server, “What IP address goes with www.myfavoritesite.com?” The DNS server, whose main purpose in life is to handle DNS queries, looks in its local records to see if it knows the answer. If it doesn’t, the DNS server queries another, higher-level domain server. That server checks its records and queries the server above it, and so on until a match is found. That name-to−IP address matching is passed back down to your computer so it can create the web request, stamp it with the right destination IP address, and send it.

The Domain Name System is critical to the operation of the Internet—if your computer can’t translate www.espn.com into 68.71.212.159, then your web browser won’t be able to access the latest scores. (As DNS is a dynamic system, the IP address may change for www.espn.com; you can check with the tracert command.)

Before sending the packet, your system will first determine if the destination IP address is on a local or remote network. In most cases, it will be on a remote network and your system will not know how to reach that remote network. Again, it would not be practical for your system to know how to directly reach every other system on the Internet, so your system will forward the packet to a network gateway. Network gateways, usually called routers, are devices that are used to interconnect networks and move packets from one network to another. That process of moving packets from one network to another is called routing and is critical to the flow of information across the Internet. To accomplish this task, routers use forwarding tables to determine where a packet should go. When a packet reaches a router, the router looks at the destination address to determine where to send the packet. If the router’s forwarding tables indicate where the packet should go, the router sends the packet out along the appropriate route. If the router does not know where the destination network is, it forwards the packet to its defined gateway, which repeats the

same process. Eventually, after traversing various networks and being passed through various routers, your packet arrives at the router serving the network with the web site you are trying to reach. This router determines the appropriate MAC address of the destination system and forwards the packet accordingly.

DNSSEC Because of the critical function DNS performs and the security implications of DNS, a cryptographically signed version of DNS was created. DNSSEC is an extension of the original DNS specification, making it trustworthy. DNS is one of the pillars of authority associated with the Internet—it provides the addresses used by machines for communications. Lack of trust in DNS and the inability to authenticate DNS messages drove the need for and creation of DNSSEC. The DNSSEC specification was formally published in 2005, but system-wide adoption has been slow. In 2008, Dan Kaminsky introduced a method of DNS cache poisoning, demonstrating the need for DNSSEC adoption. Although Kaminsky worked with virtually all major vendors and was behind one of the most coordinated patch rollouts ever, the need for DNSSEC still remains and enterprises are slow to adopt the new methods. One of the reasons for slow adoption is complexity. Having DNS requests and replies digitally signed requires significantly more work and the increase in complexity goes against the stability desires of network engineers. DNS was designed in the 1980s when the threat model was substantially

different than today. The Internet today, and its use for all kinds of critical communications, needs a trustworthy addressing mechanism. DNSSEC is that mechanism, and as it rolls out, it will significantly increase the level of trust associated with addresses. Although certificate-based digital signatures are not perfect, the level of effort to compromise this type of protection mechanism changes the nature of the attack game, making it out of reach to all but the most resourced players. The coupled nature of the trust chains in DNS also serves to alert to any intervening attacks, making attacks much harder to hide.

IP Addresses and Subnetting The last section mentioned that IPv4 addresses are 32-bit numbers. Those 32 bits are represented as four groups of 8 bits each (called octets). You will usually see IP addresses expressed as four sets of decimal numbers in dotted-decimal notation, 10.120.102.15 for example. Of those 32 bits in an IP address, some are used for the network portion of the address (the network ID), and some are used for the host portion of the address (the host ID). Subnetting is the process that is used to divide those 32 bits in an IP address and tell you how many of the 32 bits are being used for the network ID and how many are being used for the host ID. As you can guess, where and how you divide the 32 bits determines how many networks and how many host addresses you may have. To interpret the 32- bit space correctly, we must use a subnet mask, which tells us exactly how much of the space is the network portion and how much is the host portion. Let’s look at an example using the IP address 10.10.10.101 with a subnet mask of 255.255.255.0.

Tech Tip

How DNS Works DNS is a hierarchical distributed database structure of names and addresses. This system is delegated from root servers to other DNS servers that each manage local requests for information. The top level of authorities, referred to as authoritative sources, maintain the correct authoritative record. As records change, they are pushed out between DNS servers, so records can be maintained in as near a current fashion as possible. Transfers of DNS records between DNS servers are called DNS zone transfers. Because these can result in massive poisoning attacks, zone transfers need to be tightly controlled between trusted parties. To avoid request congestion, DNS responses are handled by a myriad of lower name servers, referred to as resolvers. Resolvers have a counter that refreshes their record after a time limit has been reached. Under normal operation, the DNS function is a two-step process:

1. The client requests a DNS record. 2. The resolver replies with a DNS reply.

If the resolver is out of date, the steps expand:

1. The client requests a DNS record. 2. The recursive resolver queries the authoritative server. 3. The authoritative server replies to the recursive resolver. 4. The recursive resolver replies with a DNS response to client. For a more detailed explanation of DNS, check out DNS for Rocket Scientists, www.zytrax.com/books/dns/.

First we must convert the address and subnet mask to their binary representations:

Subnet Mask: 11111111.11111111.11111111.00000000 IP Address: 00001010.00001010.00001010.01100101

Then, we perform a bitwise AND operation to get the network address. The bitwise AND operation examines each set of matching bits from the binary representation of the subnet mask and the binary representation of the IP address. For each set where both the mask and address bits are 1, the result of the AND operation is a 1. Otherwise, if either bit is a 0, the result is a 0. So, for our example we get

Network Address: 00001010.00001010.00001010.00000000

which in decimal is 10.10.10.0, the network ID of our IP network address (translate the binary representation to decimal). The network ID and subnet mask together tell us that the first three

octets of our address are network-related (10.10.10.), which means that the last octet of our address is the host portion (101 in this case). In our example, the network portion of the address is 10.10.10 and the host portion is 101. Another shortcut in identifying which of the 32 bits is being used in the network ID is to look at the subnet mask after it’s been converted to its binary representation. If there’s a 1 in the subnet mask, then the corresponding bit in the binary representation of the IP address is being used as part of the network ID. In the preceding example, the subnet mask of 255.255.255.0 in binary representation is 11111111.11111111.11111111.00000000. We can see that there’s a 1 in the first 24 spots, which means that the first 24 bits of the IP address are

being used as the network ID (which is the first three octets of 255.255.255). Network address spaces are usually divided into one of three classes:

Class A Supports 16,777,214 hosts on each network with a default subnet mask of 255.0.0.0 Subnets: 0.0.0.0 to 126.255.255.255 (127.0.0.0 to 127.255.255.255 is reserved for loopback)

Class B Supports 65,534 hosts on each network with a default subnet mask of 255.255.0.0 Subnets: 128.0.0.0 to 191.255.255.255

Class C Supports 253 hosts on each network with a default subnet mask of 255.255.255.0 (see Figure 9.10) Subnets: 192.0.0.0 to 223.255.255.255

• Figure 9.10 A subnet mask of 255.255.255.0 indicates this is a Class C address space.

Everything above 224.0.0.0 is reserved for either multicasting or future use.

Tech Tip

RFC 1918—Private Address Spaces RFC 1918 is the technical specification for private address space. RFC stands for “Request for Comment” and there are RFCs for just about everything to do with the Internet— protocols, routing, how to handle e-mail, and so on. You can find RFCs at www.ietf.org/rfc.html.

In addition, certain subnets are reserved for private use and are not routed across public networks such as the Internet:

10.0.0.0 to 10.255.255.255

172.16.0.0 to 172.31.255.255

192.168.0.0 to 192.168.255.255

169.254.0.0 to 169.254.255.255 (Automatic Private IP Addressing)

Finally, when determining the valid hosts that can be placed on a particular subnet, you have to keep in mind that the “all 0’s” address of the host portion is reserved for the network address and the “all 1’s” address of the host portion is reserved for the broadcast address of that particular subnet. Again from our earlier example:

Subnet Network Address: 10.10.10.0 00001010.00001010.00001010.00000000

Broadcast Address: 10.10.10.255 00001010.00001010.00001010.11111111

In their forwarding tables, routers maintain lists of networks and the accompanying subnet mask. With these two pieces, the router can examine

the destination address of each packet and then forward the packet on to the appropriate destination. As mentioned earlier, subnetting allows us to divide networks into

smaller logical units, and we use subnet masks to do this. But how does this work? Remember that the subnet mask tells us how many bits are being used to describe the network ID—adjusting the subnet mask (and the number of bits used to describe the network ID) allows us to divide an address space into multiple, smaller logical networks. Let’s say you have a single address space of 192.168.45.0 that you need to divide into multiple networks. The default subnet mask is 255.255.255.0, which means you’re using 24 bits as the network ID and 8 bits as the host ID. This gives you 254 different host addresses. But what if you need more networks and don’t need as many host addresses? You can simply adjust your subnet mask to borrow some of the host bits and use them as network bits. If you use a subnet mask of 255.255.255.224, you are essentially “borrowing” the first 3 bits from the space you were using to describe host IDs and using them to describe the network ID. This gives you more space to create different networks but means that each network will now have fewer available host IDs. With a 255.255.255.224 subnet mask, you can create six different subnets, but each subnet can only have 30 unique host IDs. If you borrow 6 bits from the host ID portion and use a subnet mask of 255.255.255.252, you can create 62 different networks but each of them can only have two unique host IDs.

Try This! Calculating Subnets and Hosts Given a network ID of 192.168.10.X and a subnet mask of 255.255.255.224, you should be able to create eight networks with space for 30 hosts on each network. Calculate the network address, the first usable IP address in that subnet, and the last usable IP address in that subnet. Hint: The first network will be 192.168.10.0. The first usable IP address in that subnet is 192.168.10.1 and the last usable IP address in that subnet is 192.168.10.30.

Tech Tip

Dynamic Host Configuration Protocol When an administrator sets up a network, they usually assign IP addresses to systems in one of two ways: statically or through DHCP. A static IP address assignment is fairly simple; the administrator decides what IP address to assign to a server or PC, and that IP address stays assigned to that system until the administrator decides to change it. The other popular method is through the Dynamic Host Configuration Protocol (DHCP). Under DHCP, when a system boots up or is connected to the network, it sends out a query looking for a DHCP server. If a DHCP server is available on the network, it answers the new system and temporarily assigns to the new system an IP address from a pool of dedicated, available addresses. DHCP is an “as available” protocol—if the server has already allocated all the available IP addresses in the DHCP pool, the new system will not receive an IP address and will not be able to connect to the network. Another key feature of DHCP is the ability to limit how long a system may keep its DHCP-assigned IP address. DHCP addresses have a limited lifespan, and once that time period expires, the system using that IP address must either renew use of that address or request another address from the DHCP server. The requesting system either may end up with the same IP address or may be assigned a completely new address, depending on how the DHCP server is configured and on the current demand for available addresses. DHCP is very popular in large user environments where the cost of assigning and tracking IP addresses among hundreds or thousands of user systems is extremely high.

Network Address Translation If you’re thinking that a 32-bit address space that’s chopped up and subnetted isn’t enough to handle all the systems in the world, you’re right. While IPv4 address blocks are assigned to organizations such as companies and universities, there usually aren’t enough Internet-visible IP addresses to assign to every system on the planet a unique, Internet- routable IP address. To compensate for this lack of available IP address space, we use Network Address Translation (NAT). NAT translates private (nonroutable) IP addresses into public (routable) IP addresses. From our discussions earlier in this chapter, you may remember that

certain IP address blocks are reserved for “private use,” and you’d probably agree that not every system in an organization needs a direct, Internet-routable IP address. Actually, for security reasons, it’s much

better if most of an organization’s systems are hidden from direct Internet access. Most organizations build their internal networks using the private IP address ranges (such as 10.1.1.X) to prevent outsiders from directly accessing those internal networks. However, in many cases those systems still need to be able to reach the Internet. This is accomplished by using a NAT device (typically a firewall or router) that translates the many internal IP addresses into one of a small number of public IP addresses. For example, consider a fictitious company, ACME.com. ACME has

several thousand internal systems using private IP addresses in the 10.X.X.X range. To allow those IPs to communicate with the outside world, ACME leases an Internet connection and a few public IP addresses, and deploys a NAT-capable device. ACME administrators configure all their internal hosts to use the NAT device as their default gateway. When internal hosts need to send packets outside the company, they send them to the NAT device. The NAT device removes the internal source IP address out of the outbound packets and replaces it with the NAT device’s public, routable address and sends them on their way. When response packets are received from outside sources, the device performs NAT in reverse, stripping off the external, public IP address in the destination address field and replacing it with the correct internal, private IP address in the destination address field and replacing it with the correct internal, private IP address before sending it on into the private ACME.com network. Figure 9.11 illustrates this NAT process.

• Figure 9.11 Logical depiction of NAT

Tech Tip

Different Approaches for Implementing NAT While the concept of NAT remains the same, there are actually several different approaches to implementing NAT. For example:

Static NAT Maps an internal, private address to an external, public address. The same public address is always used for that private address. This technique is often used when hosting something you wish the public to be able to get to, such as a web server, behind a firewall.

Dynamic NAT Maps an internal, private IP address to a public IP address selected from a pool of registered (public) IP addresses. This technique is often used when translating addresses for end-user workstations and the NAT device must keep track of internal/external address mappings.

Port Address Translation (PAT) Allows many different internal, private addresses to share a single external IP address. Devices performing PAT replace the source IP address

with the NAT IP address and replace the source port field with a port from an available connection pool. PAT devices keep a translation table to track which internal hosts are using which ports so that subsequent packets can be stamped with the same port number. When response packets are received, the PAT device reverses the process and forwards the packet to the correct internal host. PAT is a very popular NAT technique and in use at many organizations.

In Figure 9.11, we see an example of NAT being performed. An internal workstation (10.10.10.12) wants to visit the ESPN web site at www.espn.com (68.71.212.159). When the packet reaches the NAT device, the device translates the 10.10.10.12 source address to the globally routable 63.69.110.110 address, the IP address of the device’s externally visible interface. When the ESPN web site responds, it responds to the device’s address just as if the NAT device had originally requested the information. The NAT device must then remember which internal workstation requested the information and route the packet to the appropriate destination.

Security Zones The first aspect of security is a layered defense. Just as a castle has a moat, an outside wall, an inside wall, and even a keep, so, too, does a modern secure network have different layers of protection. Different zones are designed to provide layers of defense, with the outermost layers providing basic protection and the innermost layers providing the highest level of protection. A constant issue is that accessibility tends to be inversely related to level of protection, so it is more difficult to provide complete protection and unfettered access at the same time. Trade-offs between access and security are handled through zones, with successive zones guarded by firewalls enforcing ever-increasingly strict security policies. The outermost zone is the Internet, a free area, beyond any specific controls. Between the inner, secure corporate network and the Internet is an area where machines are considered at risk. This zone has come to be called the DMZ, after its military counterpart, the demilitarized zone,

where neither side has any specific controls. Once inside the inner, secure network, separate branches are frequently carved out to provide specific functionality; under this heading, we will also discuss intranets, extranets, flat networks, enclaves, virtual LANs (VLANs), and zones and conduits.

DMZ The DMZ is a military term for ground separating two opposing forces, by agreement and for the purpose of acting as a buffer between the two sides. A DMZ in a computer network is used in the same way; it acts as a buffer zone between the Internet, where no controls exist, and the inner, secure network, where an organization has security policies in place (see Figure 9.12). To demarcate the zones and enforce separation, a firewall is used on each side of the DMZ. The area between these firewalls is accessible from either the inner, secure network or the Internet. Figure 9.12 illustrates these zones as caused by firewall placement. The firewalls are specifically designed to prevent access across the DMZ directly, from the Internet to the inner, secure network. It is important to note that typically only filtered Internet traffic is allowed into the DMZ. For example, an organization hosting a web server and an FTP server in its DMZ may want the public to be able to “see” those services but nothing else. In that case the firewall may allow FTP, HTTP, and HTTPS traffic into the DMZ from the Internet and then filter out everything else.

• Figure 9.12 The DMZ and zones of trust

Special attention should be paid to the security settings of network devices placed in the DMZ, and they should be considered at all times to be at risk for compromise by unauthorized use. A common industry term, hardened operating system, applies to machines whose functionality is locked down to preserve security—unnecessary services and software are removed or disabled, functions are limited, and so on. This approach needs to be applied to the machines in the DMZ, and although it means that their functionality is limited, such precautions ensure that the machines will work properly in a less-secure environment. Many types of servers belong in this area, including web servers that are

serving content to Internet users, as well as remote access servers and external e-mail servers. In general, any server directly accessed from the outside, untrusted Internet zone needs to be in the DMZ. Other servers should not be placed in the DMZ. Domain name servers for your inner,

trusted network and database servers that house corporate databases should not be accessible from the outside. Application servers, file servers, print servers—all of the standard servers used in the trusted network—should be behind both firewalls and the routers and switches used to connect these machines. The idea behind the use of the DMZ topology is to provide publicly

visible services without allowing untrusted users access to your internal network. If the outside user makes a request for a resource from the trusted network, such as a data element from an internal database that is accessed via a publicly visible web page in the DMZ, then this request needs to follow this scenario:

1. A user from the untrusted network (the Internet) requests data via a web page from a web server in the DMZ.

2. The web server in the DMZ requests the data from the application server, which can be in the DMZ or in the inner, trusted network.

3. The application server requests the data from the database server in the trusted network.

4. The database server returns the data to the requesting application server.

5. The application server returns the data to the requesting web server. 6. The web server returns the data to the requesting user from the

untrusted network.

Exam Tip: DMZs act as a buffer zone between unprotected areas of a network (the Internet) and protected areas (sensitive company data stores), allowing for the monitoring and regulation of traffic between these two zones.

This separation accomplishes two specific, independent tasks. First, the user is separated from the request for data on a secure network. By having

intermediaries do the requesting, this layered approach allows significant security levels to be enforced. Users do not have direct access or control over their requests, and this filtering process can put controls in place. Second, scalability is more easily realized. The multiple-server solution can be made to be very scalable, literally to millions of users, without slowing down any particular layer.

Internet The Internet is a worldwide connection of networks and is used to transport e-mail, files, financial records, remote access—you name it— from one network to another. The Internet is not a single network, but a series of interconnected networks that allows protocols to operate and enable data to flow across it. This means that even if your network doesn’t have direct contact with a resource, as long as a neighbor, or a neighbor’s neighbor, and so on, can get there, so can you. This large web allows users almost infinite ability to communicate between systems.

There are over 3.2 billion users on the Internet, and English is the most used language.

Because everything and everyone can access this interconnected web and it is outside of your control and ability to enforce security policies, the Internet should be considered an untrusted network. A firewall should exist at any connection between your trusted network and the Internet. This is not to imply that the Internet is a bad thing—it is a great resource for all networks and adds significant functionality to our computing environments. The term World Wide Web (WWW) is frequently used synonymously

to represent the Internet, but the WWW is actually just one set of services available via the Internet. WWW or “the Web” is more specifically the Hypertext Transfer Protocol (HTTP)–based services that are made

available over the Internet. This can include a variety of actual services and content, including text files, pictures, streaming audio and video, and even viruses and worms.

Intranet An intranet describes a network that has the same functionality as the Internet for users but lies completely inside the trusted area of a network and is under the security control of the system and network administrators. Typically referred to as campus or corporate networks, intranets are used every day in companies around the world. An intranet allows a developer and a user the full set of protocols—HTTP, FTP, instant messaging, and so on—that is offered on the Internet, but with the added advantage of trust from the network security. Content on intranet web servers is not available over the Internet to untrusted users. This layer of security offers a significant amount of control and regulation, allowing users to fulfill business functionality while ensuring security. Two methods can be used to make information available to outside

users: Duplication of information onto machines in the DMZ can make it available to other users. Proper security checks and controls should be made prior to duplicating the material to ensure security policies concerning specific data availability are being followed. Alternatively, extranets (discussed in the next section) can be used to publish material to trusted partners.

Exam Tip: An intranet is a private, internal network that uses common network technologies (such as HTTP, FTP, and so on) to share information and provide resources to organizational users.

Should users inside the intranet require access to information from the Internet, a proxy server can be used to mask the requestor’s location. This

helps secure the intranet from outside mapping of its actual topology. All Internet requests go to the proxy server. If a request passes filtering requirements, the proxy server, assuming it is also a cache server, looks in its local cache of previously downloaded web pages. If it finds the page in its cache, it returns the page to the requestor without needing to send the request to the Internet. If the page is not in the cache, the proxy server, acting as a client on behalf of the user, uses one of its own IP addresses to request the page from the Internet. When the page is returned, the proxy server relates it to the original request and forwards it on to the user. This masks the user’s IP address from the Internet. Proxy servers can perform several functions for a firm; for example, they can monitor traffic requests, eliminating improper requests such as inappropriate content for work. They can also act as a cache server, cutting down on outside network requests for the same object. Finally, proxy servers protect the identity of internal IP addresses using NAT, although this function can also be accomplished through a router or firewall using NAT as well.

Extranet An extranet is an extension of a selected portion of a company’s intranet to external partners. This allows a business to share information with customers, suppliers, partners, and other trusted groups while using a common set of Internet protocols to facilitate operations. Extranets can use public networks to extend their reach beyond a company’s own internal network, and some form of security, typically VPN, is used to secure this channel. The use of the term extranet implies both privacy and security. Privacy is required for many communications, and security is needed to prevent unauthorized use and events from occurring. Both of these functions can be achieved through the use of technologies described in this chapter and other chapters in this book. Proper firewall management, remote access, encryption, authentication, and secure tunnels across public networks are all methods used to ensure privacy and security for extranets.

Exam Tip: An extranet is a semiprivate network that uses common network technologies (such as HTTP, FTP, and so on) to share information and provide resources to business partners. Extranets can be accessed by more than one company, because they share information between organizations.

Flat Networks As networks have become more complex, with multiple layers of tiers and interconnections, a problem can arise in connectivity. One of the limitations of the Spanning Tree Protocol (STP) is its inability to manage Layer 2 traffic efficiently across highly complex networks. STP was created to prevent loops in Layer 2 networks and has been improved to the current version of Rapid Spanning Tree Protocol (RSTP). RSTP creates a spanning tree within the network of Layer 2 switches, disabling links that are not part of the spanning tree. RSTP, IEEE 802.1w, provides a more rapid convergence to a new spanning tree solution after topology changes are detected. The problem with the spanning tree algorithms is that the network traffic is interrupted while the system recalculates and reconfigures. These disruptions can cause problems in network efficiencies and have led to a push for flat network designs, which avoid packet- looping issues through an architecture that does not have tiers. One name associated with flat network topologies is network fabric, a

term meant to describe a flat, depthless network. These are becoming increasingly popular in data centers, and other areas of high traffic density, as they can offer increased throughput and lower levels of network jitter and other disruptions. While this is good for efficiency of network operations, this “everyone can talk to everyone” idea is problematic with respect to security.

Enclaves

Modern networks, with their increasingly complex connections, result in systems where navigation can become complex between nodes. Just as a DMZ-based architecture allows for differing levels of trust, the isolation of specific pieces of the network using security rules can provide differing trust environments. The concept of breaking a network into enclaves can create areas of trust where special protections can be employed and traffic from outside the enclave is limited or properly screened before admission. Enclaves are not diametrically opposed to the concept of a flat network

structure; they are just carved-out areas, like gated neighborhoods, where one needs special credentials to enter. A variety of security mechanisms can be employed to create a secure enclave. Layer 2 addressing (subnetting) can be employed, making direct addressability an issue. Firewalls, routers, and application-level proxies can be employed to screen packets before entry or exit from the enclave. Even the people side of the system can be restricted through the use of a special set of sysadmins to manage the systems. Enclaves are an important tool in modern secure network design. Figure

9.13 shows a network design with a standard two-firewall implementation of a DMZ. On the internal side of the network, multiple firewalls can be seen, carving off individual security enclaves, zones where the same security rules apply. Common enclaves include those for high-security databases, low-security users (call centers), public-facing kiosks, and the management interfaces to servers and network devices. Having each of these in its own zone provides for more security control. On the management layer, using a nonroutable IP address scheme for all of the interfaces prevents them from being directly accessed from the Internet.

• Figure 9.13 Secure enclaves

VLANs A LAN is a set of devices with similar functionality and similar communication needs, typically co-located and operated off a single switch. This is the lowest level of a network hierarchy and defines the domain for certain protocols at the data link layer for communication. A virtual LAN (VLAN) is a logical implementation of a LAN and allows computers connected to different physical networks to act and communicate as if they were on the same physical network. A VLAN has many of the same characteristic attributes of a LAN and behaves much like a physical LAN but is implemented using switches and software. This very powerful technique allows significant network flexibility, scalability, and performance and allows administrators to perform network reconfigurations without having to physically relocate or recable systems.

Exam Tip: A broadcast domain is a logical division of a computer network. Systems connected to a broadcast domain can communicate with each other as if they were connected to the same physical network even when they are not.

Trunking Trunking is the process of spanning a single VLAN across multiple switches. A trunk-based connection between switches allows packets from a single VLAN to travel between switches, as shown in Figure 9.14. Two trunks are shown in the figure: VLAN 10 is implemented with one trunk and VLAN 20 is implemented with the other. Hosts on different VLANs cannot communicate using trunks and thus are switched across the switch network. Trunks enable network administrators to set up VLANs across multiple switches with minimal effort. With a combination of trunks and VLANs, network administrators can subnet a network by user functionality without regard to host location on the network or the need to recable machines.

• Figure 9.14 VLANs and trunks

Security Implications VLANs are used to divide a single network into multiple subnets based on functionality. This permits accounting and marketing, for example, to share a switch because of proximity yet still have separate traffic domains. The physical placement of equipment and cables is logically and programmatically separated so that adjacent ports on a switch can reference separate subnets. This prevents unauthorized use of physically

close devices through separate subnets that are on the same equipment. VLANs also allow a network administrator to define a VLAN that has no users and map all of the unused ports to this VLAN (some managed switches allow administrators to simply disable unused ports as well). Then, if an unauthorized user should gain access to the equipment, that user will be unable to use unused ports, as those ports will be securely defined to nothing. Both a purpose and a security strength of VLANs is that systems on separate VLANs cannot directly communicate with each other.

Trunks and VLANs have security implications that you need to heed so that firewalls and other segmentation devices are not breached through their use. You also need to understand how to use trunks and VLANs, to prevent an unauthorized user from reconfiguring them to gain undetected access to secure portions of a network.

Zones and Conduits The terms zones and conduits have specialized meaning in control system networks. Control systems are the computers used to control physical processes, ranging from traffic lights to refineries, manufacturing plants, critical infrastructure, and more. These networks are now being attached to enterprise networks and this will result in the inclusion of control system network terminology into IT/network/security operations terminology. A term commonly used in control system networks is zone. A zone is a grouping of elements that share common security requirements. A conduit is defined as the path for the flow of data between zones. Zones are similar to enclaves in that they have a defined set of common

security requirements that differ from outside the zone. The zone is marked on a diagram, indicating the boundary between what is in and outside the zone. All data flows in or out of a zone must be by a defined conduit. The conduit allows a means to focus the security function on the

data flows, ensuring the appropriate conditions are met before data enters or leaves a zone.

Tunneling Tunneling is a method of packaging packets so that they can traverse a network in a secure, confidential manner. Tunneling involves encapsulating packets within packets, enabling dissimilar protocols to coexist in a single communication stream, as in IP traffic routed over an Asynchronous Transfer Mode (ATM) network. Tunneling also can provide significant measures of security and confidentiality through encryption and encapsulation methods. The best example of this is a VPN that is established over a public network through the use of a tunnel, as shown in Figure 9.15, connecting a firm’s Boston office to its New York City (NYC) office.

• Figure 9.15 Tunneling across a public network

Assume, for example, that a company has multiple locations and decides to use the public Internet to connect the networks at these locations. To make these connections secure from outside unauthorized use, the company can employ a VPN connection between the different networks. On each network, an edge device, usually a router or VPN concentrator, connects to another edge device on the other network. Then, using IPsec protocols, these routers establish a secure, encrypted path between them.

This securely encrypted set of packets cannot be read by outside routers; only the addresses of the edge routers are visible. This arrangement acts as a tunnel across the public Internet and establishes a private connection, secure from outside snooping or use. Because of ease of use, low-cost hardware, and strong security, tunnels

and the Internet are a combination that will see more use in the future. IPsec, VPN, and tunnels will become a major set of tools for users requiring secure network connections across public segments of networks. For more information on VPNs and remote access, refer to Chapter 11.

A VPN concentrator is a specialized piece of hardware designed to handle the encryption and decryption required for remote, secure access to an organization’s network.

Storage Area Networks Storage area networks (SANs) are systems which provide remote storage of data across a network connection. The design of SAN protocols is such that the disk appears to actually be on the client machine as a local drive rather than as attached storage, as in network attached storage (NAS). This makes the disk visible in disk and volume management utilities and allows their functionality. Common SAN protocols include iSCSI and Fibre Channel.

iSCSI The Internet Small Computer System Interface (iSCSI) is a protocol for IP-based storage. iSCSI can be used to send data over existing network infrastructures, enabling SANs. Positioned as a low-cost alternative to Fibre Channel storage, the only real limitation is one of network bandwidth.

Fibre Channel Fibre Channel (FC) is a high-speed network technology (with throughput up to 16 Gbps) used to connect storage to computer systems. The FC protocol is a transport protocol similar to the TCP protocol in IP networks. Carried via special cables, one of the drawbacks of FC-based storage is cost.

FCoE The Fibre Channel over Ethernet (FCoE) protocol encapsulates the FC frames, enabling FC communication over 10-Gigabit Ethernet networks.

Chapter 9 Review

For More Information Networking CompTIA Network+ Certification All-in-One Exam Guide, Premium Fifth Edition, McGraw-Hill, 2014

The Internet Engineering Task Force www.ietf.org

Wikipedia articles: Routing http://en.wikipedia.org/wiki/Routing NAT http://en.wikipedia.org/wiki/Network_address_translation ICMP http://en.wikipedia.org/wiki/Internet_Control_Message_Protocol

Subnetting http://en.wikipedia.org/wiki/Subnetting

Lab Manual Exercises The following lab exercises from the companion lab manual, Principles of Computer Security Lab Manual, Fourth Edition, provide practical application of material covered in this chapter:

Chapter Summary After reading this chapter and completing the exercises, you should understand the following about networks.

Identify the basic network architectures

There are two broad categories of networks: LANs and WANs.

The physical arrangement of a network is typically called the network’s topology.

There are four main types of network topologies: ring, bus, star, and mixed.

Define the basic network protocols

Protocols, agreed-upon formats for exchanging or transmitting data between systems, enable computers to communicate.

When data is transmitted over a network, it is usually broken up into smaller pieces called packets.

Most protocols define the types and format for packets used in that protocol.

TCP is connection oriented, requires the three-way handshake to initiate a connection, and provides guaranteed and reliable data delivery.

UDP is connectionless, lightweight, and provides limited error checking and no delivery guarantee.

Each network device has a unique hardware address known as a MAC address. The MAC address is used for packet delivery.

Network devices are also typically assigned a 32-bit number known as an IP address.

The Domain Name Service (DNS) translates names, like www.cnn.com, into IP addresses.

Explain routing and address translation

The process of moving packets from one end device to another through different networks is called routing.

Subnetting is the process of dividing a network address space into smaller networks.

DHCP allows network devices to be automatically configured on a network and temporarily assigned an IP address.

Network Address Translation (NAT) converts private, internal IP addresses to public, routable IP addresses and vice versa.

Classify security zones

A DMZ is a buffer zone between networks with different trust levels. Companies often place public resources in a DMZ so that Internet users and internal users may access those resources without exposing the internal company network to the Internet.

An intranet is a private, internal network that uses common network technologies (such as HTTP, FTP, and so on) to share information and provide resources to organizational users.

An extranet is a semiprivate network that uses common network technologies (such as HTTP, FTP, and so on) to share information and provide resources to business partners.

An enclave is a specialized security zone with common security requirements.

A VLAN (or virtual LAN) is a group of ports on a switch that is configured to create a logical network of computer that appears to be connected to the same network even if they are located on different physical network segments. Systems on a VLAN can communicate with each other but cannot communicate directly with systems on other VLANs.

Trunking is the process of spanning a single VLAN across multiple switches.

Tunneling is a method of packaging packets so that they can traverse a network in a secure, confidential manner.

Key Terms Address Resolution Protocol (ARP) (234) bus topology (222) datagram (226) denial-of-service (DoS) (229)

Domain Name System (DNS) (235) DMZ (240) Dynamic Host Configuration Protocol (DHCP) (238) enclave (243) Ethernet (233) extranet (243) flat network (243) Internet Control Message Protocol (ICMP) (229) Internet Protocol (IP) (226) intranet (242) local area network (LAN) (221) Media Access Control (MAC) address (233) Network Address Translation (NAT) (238) network (220) packet (225) protocol (223) ring topology (222) routing (235) star topology (222) storage area network (SAN) (221) subnetting (236) subnet mask (236) three-way handshake (228) topology (222) Transmission Control Protocol (TCP) (228) trunking (245) tunneling (246) User Datagram Protocol (UDP) (228) virtual local area network (VLAN) (222) wide area network (WAN) (221)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. A(n) _______________ is a group of two or more devices linked together to share data.

2. A packet in an IP network is sometimes called a(n) _______________.

3. Moving packets from source to destination across multiple networks is called ____________.

4. The _______________ is the hardware address used to uniquely identify each device on a network.

5. A(n) _______________ tells you what portion of a 32-bit IP address is being used as the network ID and what portion is being used as the host ID.

6. The shape or arrangement of a network, such as bus, star, ring, or mixed, is known as the _______________ of the network.

7. A small, typically local network covering a relatively small area such as a single floor of an office building is called a(n) _______________.

8. A(n) _______________ is an agreed-upon format for exchanging information between systems.

9. The packet exchange sequence (SYN, SYN/ACK, ACK) that initiates a TCP connection is called the _______________.

10. _______________ is the protocol that allows the use of private, internal IP addresses for internal traffic and public IP addresses for external traffic.

Multiple-Choice Quiz 1. What is Layer 1 of the OSI model called?

A. The physical layer

B. The network layer

C. The initial layer

D. The presentation layer

2. The UDP protocol: A. Provides excellent error-checking algorithms

B. Is a connectionless protocol

C. Guarantees delivery of packets

D. Requires a permanent connection between source and destination

3. The process that dynamically assigns an IP address to a network device is called:

A. NAT

B. DNS

C. DHCP

D. Routing

4. What is the three-way handshake sequence used to initiate TCP connections?

A. ACK, SYN/ACK, ACK

B. SYN, SYN/ACK, ACK

C. SYN, SYN, ACK/ACK

D. ACK, SYN/ACK, SYN

5. Which of the following is a control and information protocol used by network devices to determine such things as a remote network’s availability and the length of time required to reach a remote network?

A. UDP

B. NAT

C. TCP

D. ICMP

6. What is the name of the protocol that translates names into IP addresses?

A. TCP

B. DNS

C. ICMP

D. DHCP

7. Dividing a network address space into smaller, separate networks is called what?

A. Translating

B. Network configuration

C. Subnetting

D. Address translation

8. Which protocol translates private (nonroutable) IP addresses into public (routable) IP addresses?

A. NAT

B. DHCP

C. DNS

D. ICMP

9. The TCP protocol: A. Is connectionless

B. Provides no error checking

C. Allows for packets to be processed in the order they were sent

D. Has no overhead

10. Which of the following would be a valid MAC address? A. 00:07:e9

B. 00:07:e9:7c:c8

C. 00:07:e9:7c:c8:aa

D. 00:07:e9:7c:c8:aa:ba

Essay Quiz 1. A developer in your company is building a new application and has

asked you if it should use TCP- or UDP-based communications. Provide her with a brief discussion of the advantages and disadvantages of each protocol.

2. Your boss wants to know if DHCP is appropriate for both server and PC environments. Provide her with your opinion and be sure to include a discussion of how DHCP works.

3. Describe the three basic types of network topologies and provide a sample diagram of each type.

4. Describe the three-way handshake process used to initiate TCP

connections.

5. Your boss wants to know how subnetting works. Provide her with a brief description and be sure to include an example to illustrate how subnetting works.

Lab Projects

• Lab Project 9.1 A client of yours only has five external, routable IP addresses but has over 50 systems that it wants to be able to reach the Internet for web surfing, e-mail, and so on. Design a network solution for the client that addresses their immediate needs but will still let them grow in the future.

• Lab Project 9.2 Your boss wants you to learn how to use the arp and nslookup commands. Find a Windows machine and open a command/DOS prompt. Type in arp and press ENTER to see the options for the arp command. Use the arp command to find the MAC address of your system and at least five other systems on your network. When you are finished with arp, type in nslookup and press ENTER. At the prompt, type in the name of your favorite web site, such as www.cnn.com. The nslookup command will return the IP addresses that match that domain name. Find the IP addresses of at least five different web sites.

chapter 10 Infrastructure Security

The higher your structure is to be, the deeper must be its foundation.

—SAINT AUGUSTINE

I

In this chapter, you will learn how to

Construct networks using different types of network devices

Enhance security using security devices

Enhance security using NAC/NAP methodologies

Identify the different types of media used to carry network signals

Describe the different types of storage media used to store information

Use basic terminology associated with network functions related to information security

Describe the different types and uses of cloud computing

nfrastructure security begins with the design of the infrastructure itself. The proper use of components improves not only performance but security as well. Network components are not isolated from the

computing environment and are an essential aspect of a total computing environment. From the routers, switches, and cables that connect the devices, to the firewalls and gateways that manage communication, from the network design, to the protocols that are employed—all these items play essential roles in both performance and security.

Devices A complete network computer solution in today’s business environment consists of more than just client computers and servers. Devices are needed to connect the clients and servers and to regulate the traffic between them. Devices are also needed to expand this network beyond simple client computers and servers to include yet other devices, such as wireless and handheld systems. Devices come in many forms and with many functions, from hubs and switches, to routers, wireless access points, and special- purpose devices such as virtual private network (VPN) devices. Each device has a specific network function and plays a role in maintaining

network infrastructure security.

Cross Check The Importance of Availability In Chapter 2, we examined the CIA of security: confidentiality, integrity, and availability. Unfortunately, the availability component is often overlooked, even though availability is what has moved computing into the modern networked framework and plays a significant role in security. Security failures can occur in two ways. First, a failure can allow unauthorized users access to

resources and data they are not authorized to use, compromising information security. Second, a failure can prevent a user from accessing resources and data the user is authorized to use. This second failure is often overlooked, but it can be as serious as the first. The primary goal of network infrastructure security is to allow all authorized use and deny all unauthorized use of resources.

Workstations Most users are familiar with the client computers used in the client/server model called workstation devices. The workstation is the machine that sits on the desktop and is used every day for sending and reading e-mail, creating spreadsheets, writing reports in a word processing program, and playing games. If a workstation is connected to a network, it is an important part of the security solution for the network. Many threats to information security can start at a workstation, but much can be done in a few simple steps to provide protection from many of these threats.

Cross Check Workstations and Servers Servers and workstations are key nodes on networks. The specifics for securing these devices ares covered in Chapter 14.

Servers Servers are the computers in a network that host applications and data for everyone to share. Servers come in many sizes, from small single-CPU boxes that may be less powerful than a workstation, to multiple-CPU monsters, up to and including mainframes. The operating systems used by servers range from Windows Server, to UNIX, to Multiple Virtual Storage (MVS) and other mainframe operating systems. The OS on a server tends to be more robust than the OS on a workstation system and is designed to service multiple users over a network at the same time. Servers can host a variety of applications, including web servers, databases, e-mail servers, file servers, print servers, and application servers for middleware applications.

Virtualization Virtualization technology is used to allow a computer to have more than one OS present and, in many cases, operating at the same time. Virtualization is an abstraction of the OS layer, creating the ability to host multiple OSs on a single piece of hardware. One of the major advantages of virtualization is the separation of the software and the hardware, creating a barrier that can improve many system functions, including security. The underlying hardware is referred to as the host machine, and on it is a host OS. Either the host OS has built-in hypervisor capability or an application is needed to provide the hypervisor function to manage the virtual machines (VMs). The virtual machines are typically referred to as the guest OSs.

Exam Tip: A hypervisor is the interface between a virtual machine and the host machine hardware. Hypervisors are the layer that enables virtualization.

Newer OSs are designed to natively incorporate virtualization hooks, enabling virtual machines to be employed with greater ease. There are several common virtualization solutions, including Microsoft Hyper-V, VMware, Oracle VM VirtualBox, Parallels, and Citrix Xen. It is important to distinguish between virtualization and boot loaders that allow different OSs to boot on hardware. Apple’s Boot Camp allows you to boot into Microsoft Windows on Apple hardware. This is different from Parallels, a product with complete virtualization capability for Apple hardware. Virtualization offers much in terms of host-based management of a

system. From snapshots that allow easy rollback to previous states, faster system deployment via preconfigured images, ease of backup, and the ability to test systems, virtualization offers many advantages to system owners. The separation of the operational software layer from the hardware layer can offer many improvements in the management of systems.

Snapshots A snapshot is a point-in-time saving of the state of a virtual machine. Snapshots have great utility because they are like a savepoint for an entire system. Snapshots can be used to roll a system back to a previous point in time, undo operations, or provide a quick means of recovery from a complex, system-altering change that has gone awry. Snapshots act as a form of backup and are typically much faster than normal system backup and recovery operations.

Patch Compatibility Having an OS operate in a virtual environment does not change the need for security associated with the OS. Patches are still needed and should be applied, independent of the virtualization status. Because of the nature of a virtual environment, it should have no effect on the utility of patching, as the patch is for the guest OS.

Host Availability/Elasticity When you set up a virtualization environment, protecting the host OS and hypervisor level is critical for system stability. The best practice is to avoid the installation of any applications on the host-level machine. All apps should be housed and run in a virtual environment. This aids in the stability by providing separation between the application and the host OS. The term elasticity refers to the ability of a system to expand/contract as system requirements dictate. One of the advantages of virtualization is that a virtual machine can be moved to larger or smaller environments based on needs. If a VM needs more processing power, then migrating the VM to a new hardware system with greater CPU capacity allows the system to expand without having to rebuild it.

Security Control Testing When applying security controls to a system to manage security operations, it is important to test the controls to ensure that they are providing the desired results. Putting a system into a VM does not change this requirement. In fact, it may complicate it because of the nature of the guest OS to hypervisor relationship. It is essential to specifically test all security controls inside the virtual environment to ensure their behavior is still effective.

Sandboxing Sandboxing refers to the quarantine or isolation of a system from its surroundings. Virtualization can be used as a form of sandboxing with respect to an entire system. You can build a VM, test something inside the VM, and, based on the results, make a decision with regard to stability or whatever concern was present.

Mobile Devices Mobile devices such as laptops, tablets, and mobile phones are the latest

devices to join the corporate network. Mobile devices can create a major security gap, as a user may access separate e-mail accounts, one personal, without antivirus protection, and the other corporate. Mobile devices are covered in detail in Chapter 12.

Device Security, Common Concerns As more and more interactive devices (that is, devices you can interact with programmatically) are being designed, a new threat source has appeared. In an attempt to build security into devices, typically, a default account and password must be entered to enable the user to access and configure the device remotely. These default accounts and passwords are well known in the hacker community, so one of the first steps you must take to secure such devices is to change the default credentials. Anyone who has purchased a home office router knows the default configuration settings and can check to see if another user has changed theirs. If they have not, this is a huge security hole, allowing outsiders to “reconfigure” their network devices.

Tech Tip

Default Accounts Always reconfigure all default accounts on all devices before exposing them to external traffic. This is to prevent others from reconfiguring your devices based on known access settings.

Network Attached Storage Because of the speed of today’s Ethernet networks, it is possible to manage data storage across the network. This has led to a type of storage known as Network Attached Storage (NAS). The combination of inexpensive hard drives, fast networks, and simple application-based

servers has made NAS devices in the terabyte range affordable for even home users. Because of the large size of video files, this has become popular for some users as a method of storing TV and video libraries. Because NAS is a network device, it is susceptible to various attacks, including sniffing of credentials and a variety of brute-force attacks to obtain access to the data.

Removable Storage Because removable devices can move data outside of the corporate- controlled environment, their security needs must be addressed. Removable devices can bring unprotected or corrupted data into the corporate environment. All removable devices should be scanned by antivirus software upon connection to the corporate environment. Corporate policies should address the copying of data to removable devices. Many mobile devices can be connected via USB to a system and used to store data—and in some cases vast quantities of data. This capability can be used to avoid some implementations of data loss prevention mechanisms.

Networking Networks are used to connect devices together. Networks are composed of components that perform networking functions to move data between devices. Networks begin with network interface cards, then continue in layers of switches and routers. Specialized networking devices are used for specific purposes, such as security and traffic management.

Network Interface Cards To connect a server or workstation to a network, a device known as a network interface card (NIC) is used. A NIC is a card with a connector port for a particular type of network connection, either Ethernet or Token

Ring. The most common network type in use for LANs is the Ethernet protocol, and the most common connector is the RJ-45 connector. A NIC is the physical connection between a computer and the network.

The purpose of a NIC is to provide lower-level protocol functionality from the OSI (Open System Interconnection) model. Because the NIC defines the type of physical layer connection, different NICs are used for different physical protocols. NICs come as single-port and multiport, and most workstations use only a single-port NIC, as only a single network connection is needed. Figure 10.1 shows a common form of a NIC. For servers, multiport NICs are used to increase the number of network connections, increasing the data throughput to and from the network.

• Figure 10.1 Linksys network interface card (NIC)

Each NIC port is serialized with a unique code, 48 bits long, referred to as a Media Access Control address (MAC address). These are created by the manufacturer, with 24 bits representing the manufacturer and 24 bits being a serial number, guaranteeing uniqueness. MAC addresses are used in the addressing and delivery of network packets to the correct machine and in a variety of security situations. Unfortunately, these addresses can be changed, or “spoofed,” rather easily. In fact, it is common for personal routers to clone a MAC address to allow users to use multiple devices over a network connection that expects a single MAC.

Hubs A hub is networking equipment that connects devices that are using the same protocol at the physical layer of the OSI model. A hub allows multiple machines in an area to be connected together in a star configuration, with the hub as the center. This configuration can save significant amounts of cable and is an efficient method of configuring an Ethernet backbone. All connections on a hub share a single collision domain, a small cluster in a network where collisions occur. As network traffic increases, it can become limited by collisions. The collision issue has made hubs obsolete in newer, higher performance networks, with inexpensive switches and switched Ethernet keeping costs low and usable bandwidth high. Hubs also create a security weakness in that all connected devices see all traffic, enabling sniffing and eavesdropping to occur. In today’s networks, hubs have all but disappeared, being replaced by low- cost switches.

Tech Tip

Device/OSI Level Interaction

Different network devices operate using different levels of the OSI networking model to move packets from device to device:

Bridges Bridges are networking equipment that connect devices using the same protocol at the data link layer of the OSI model. A bridge operates at the data link layer, filtering traffic based on MAC addresses. Bridges can reduce collisions by separating pieces of a network into two separate collision domains, but this only cuts the collision problem in half. Although bridges are useful, a better solution is to use switches for network connections.

Switches A switch forms the basis for connections in most Ethernet-based LANs. Although hubs and bridges still exist, in today’s high-performance network environment, switches have replaced both. A switch has separate collision

domains for each port. This means that for each port, two collision domains exist: one from the port to the client on the downstream side, and one from the switch to the network upstream. When full duplex is employed, collisions are virtually eliminated from the two nodes, host and client. This also acts as a hub-based system, where a single sniffer can see all of the traffic to and from connected devices. Switches operate at the data link layer, while routers act at the network

layer. For intranets, switches have become what routers are on the Internet —the device of choice for connecting machines. As switches have become the primary network connectivity device, additional functionality has been added to them. A switch is usually a Layer 2 device, but Layer 3 switches incorporate routing functionality. Hubs have been replaced by switches because switches perform a

number of features that hubs cannot perform. For example, the switch improves network performance by filtering traffic. It filters traffic by only sending the data to the port on the switch that the destination system resides on. The switch knows what port each system is connected to and sends the data only to that port. The switch also provides security features, such as the option to disable a port so that it cannot be used without authorization. The switch also supports a feature called port security, which allows the administrator to control which systems can send data to each of the ports. The switch uses the MAC address of the systems to incorporate traffic filtering and port security features, which is why it is considered a Layer 2 device.

Exam Tip: MAC filtering can be employed on switches, permitting only specified MACs to connect to the switch. This can be bypassed if an attacker can learn an allowed MAC, as they can clone the permitted MAC onto their own NIC card and spoof the switch. To filter edge connections, IEEE 802.1X is more secure and is covered in Chapter 11. This can also be referred to as MAC limiting. Be careful to pay attention to context on the exam, however, because MAC limiting also can refer to preventing flooding attacks on switches by limiting the number of MAC addresses that can be “learned” by a switch.

Port address security based on MAC addresses can determine whether a packet is allowed or blocked from a connection. This is the very function that a firewall uses for its determination, and this same functionality is what allows an 802.1X device to act as an “edge device.”

Exam Tip: Network traffic segregation by switches can also act as a security mechanism, preventing access to some devices from other devices. This can prevent someone from accessing critical data servers from a machine in a public area.

One of the security concerns with switches is that, like routers, they are intelligent network devices and are therefore subject to hijacking by hackers. Should a hacker break into a switch and change its parameters, he might be able to eavesdrop on specific or all communications, virtually undetected. Switches are commonly administered using the Simple Network Management Protocol (SNMP) and Telnet protocol, both of which have a serious weakness in that they send passwords across the network in cleartext. A hacker armed with a sniffer that observes maintenance on a switch can capture the administrative password. This allows the hacker to come back to the switch later and configure it as an administrator. An additional problem is that switches are shipped with default passwords, and if these are not changed when the switch is set up, they offer an unlocked door to a hacker.

To secure a switch, you should disable all access protocols other than a secure serial line or a secure protocol such as Secure Shell (SSH). Using only secure methods to access a switch will limit the exposure to hackers and malicious users. Maintaining secure network switches is even more important than securing individual boxes, for the span of control to intercept data is much wider on a switch, especially if it’s reprogrammed by a hacker.

Switches are also subject to electronic attacks, such as ARP poisoning

and MAC flooding. ARP poisoning is where a device spoofs the MAC address of another device, attempting to change the ARP tables through spoofed traffic and the ARP table-update mechanism. MAC flooding is where a switch is bombarded with packets from different MAC addresses, flooding the switch table and forcing the device to respond by opening all ports and acting as a hub. This enables devices on other segments to sniff traffic.

Loop Protection Switches operate at Layer 2, at which there is no countdown mechanism to kill packets that get caught in loops or on paths that will never resolve. The Layer 2 space acts as a mesh, where potentially the addition of a new device can create loops in the existing device interconnections. To prevent loops, a technology called spanning trees is employed by virtually all switches. The Spanning Tree Protocol (STP) allows for multiple, redundant paths, while breaking loops to ensure a proper broadcast pattern. Loop protection is covered in detail in Chapter 9.

Routers A router is a network traffic management device used to connect different network segments together. Routers operate at the network layer (Layer 3) of the OSI model, using the network address (typically an IP address) to route traffic and using routing protocols to determine optimal routing paths across a network. Routers form the backbone of the Internet, moving traffic from network to network, inspecting packets from every communication as they move traffic in optimal paths. Routers operate by examining each packet, looking at the destination

address, and using algorithms and tables to determine where to send the packet next. This process of examining the header to determine the next hop can be done in quick fashion.

ACLs can require significant effort to establish and maintain. Creating them is a straightforward task, but their judicious use will yield security benefits with a limited amount of maintenance. Cisco routers have standard and extended ACLs; standard ACLs can filter traffic based only on the source IP address, whereas extended ACLs can filter traffic by source/destination IP address, protocol, and port. This can be very important in security zones such as a DMZ and at edge devices, blocking undesired outside contact while allowing known inside traffic.

Routers use access control lists (ACLs) as a method of deciding whether a packet is allowed to enter the network. With ACLs, it is also possible to examine the source address and determine whether or not to allow a packet to pass. This allows routers equipped with ACLs to drop packets according to rules built into the ACLs. This can be a cumbersome process to set up and maintain, and as the ACL grows in size, routing efficiency can be decreased. It is also possible to configure some routers to act as quasi– application gateways, performing stateful packet inspection and using contents as well as IP addresses to determine whether or not to permit a packet to pass. This can tremendously increase the time for a router to pass traffic and can significantly decrease router throughput. Configuring ACLs and other aspects of setting up routers for this type of use are beyond the scope of this book. One serious security concern regarding router operation is limiting who

has access to the router and control of its internal functions. Like a switch, a router can be accessed using SNMP and Telnet and programmed remotely. Because of the geographic separation of routers, this can become a necessity, for many routers in the world of the Internet can be hundreds of miles apart, in separate locked structures. Physical control over a router is absolutely necessary, for if any device, be it a server, switch, or router, is physically accessed by a hacker, it should be considered compromised. Thus, such access must be prevented. As with switches, it is important to ensure that the administrator password is never passed in the clear, that only secure mechanisms are used to access the router, and that all of the default passwords are reset to strong passwords.

As with switches, the most assured point of access for router management control is via the serial control interface port. This allows access to the control aspects of the router without having to deal with traffic-related issues. For internal company networks, where the geographic dispersion of routers may be limited, third-party solutions to allow out-of-band remote management exist. This allows complete control over the router in a secure fashion, even from a remote location, although additional hardware is required. Routers are available from numerous vendors and come in sizes big and

small. A typical small home office router for use with cable modem/DSL service is shown in Figure 10.2. Larger routers can handle traffic of up to tens of gigabytes per second per channel, using fiber-optic inputs and moving tens of thousands of concurrent Internet connections across the network. These routers, which can cost hundreds of thousands of dollars, form an essential part of e-commerce infrastructure, enabling large enterprises such as Amazon and eBay to serve many customers’ use concurrently.

• Figure 10.2 A small home office router for cable modem/DSL

Firewalls A firewall is a network device—hardware, software, or a combination thereof—whose purpose is to enforce a security policy across its connections by allowing or denying traffic to pass into or out of the network. A firewall is a lot like a gate guard at a secure facility. The guard examines all the traffic trying to enter the facility—cars with the correct sticker or delivery trucks with the appropriate paperwork are allowed in; everyone else is turned away (see Figure 10.3).

• Figure 10.3 How a firewall works

Exam Tip: A firewall is a network device (hardware, software, or combination of the two) that enforces a security policy. All network traffic passing through the firewall is examined—traffic that does not meet the specified security criteria or violates the firewall policy is blocked.

The heart of a firewall is the set of security policies that it enforces. Management determines what is allowed in the form of network traffic between devices, and these policies are used to build rule sets for the firewall devices used to filter network traffic across the network.

Tech Tip

Firewall Rules Firewalls are in reality policy enforcement devices. Each rule in a firewall should have a policy behind it, as this is the only manner of managing firewall rule sets over time. The steps for successful firewall management begin and end with maintaining a policy list by firewall of the traffic restrictions to be imposed. Managing this list via a configuration management process is important to prevent network instabilities from faulty rule sets or unknown “left- over” rules.

Orphan or left-over rules are rules that were created for a special purpose (testing, emergency, visitor or vendor, etc.) and then forgotten about and not removed after their use ended. These rules can clutter up a firewall and result in unintended challenges to the network security team.

Firewall security policies are a series of rules that defines what traffic is permissible and what traffic is to be blocked or denied. These are not universal rules, and there are many different sets of rules for a single company with multiple connections. A web server connected to the Internet may be configured only to allow traffic on port 80 for HTTP, and

have all other ports blocked. An e-mail server may have only necessary ports for e-mail open, with others blocked. A key to security policies for firewalls is the same as has been seen for other security policies—the principle of least access. Only allow the necessary access for a function; block or deny all unneeded functionality. How an organization deploys its firewalls determines what is needed for security policies for each firewall. You may even have a small office–home office firewall at your house, such as the RVS4000 shown in Figure 10.4. This device from Linksys provides both routing and firewall functions.

• Figure 10.4 Linksys RVS4000 SOHO firewall

The security topology determines what network devices are employed at what points in a network. At a minimum, the corporate connection to the Internet should pass through a firewall, as shown in Figure 10.5. This firewall should block all network traffic except that specifically authorized by the security policy. This is actually easy to do: blocking communications on a port is simply a matter of telling the firewall to close the port. The issue comes in deciding what services are needed and by

whom, and thus which ports should be open and which should be closed. This is what makes a security policy useful but, in some cases, difficult to maintain.

• Figure 10.5 Logical depiction of a firewall protecting an organization from the Internet

The perfect firewall policy is one that the end user never sees and one that never allows even a single unauthorized packet to enter the network. As with any other perfect item, it will be rare to find the perfect security policy for a firewall. To develop a complete and comprehensive security policy, it is first

necessary to have a complete and comprehensive understanding of your network resources and their uses. Once you know what your network will be used for, you will have an idea of what to permit. Also, once you understand what you need to protect, you will have an idea of what to block. Firewalls are designed to block attacks before they get to a target machine. Common targets are web servers, e-mail servers, DNS servers, FTP services, and databases. Each of these has separate functionality, and each of these has separate vulnerabilities. Once you have decided who should receive what type of traffic and what types should be blocked, you can administer this through the firewall.

Routers help control the flow of traffic into and out of your network. Through the use of ACLs, routers can act as first-level firewalls and can help weed out malicious traffic.

How Do Firewalls Work? Firewalls enforce the established security policies. They can do this through a variety of mechanisms, including:

Network Address Translation (NAT) As you may remember from Chapter 9, NAT translates private (nonroutable) IP addresses into public (routable) IP addresses.

Basic packet filtering Basic packet filtering looks at each packet entering or leaving the network and then either accepts the packet or rejects the packet based on user-defined rules. Each packet is examined separately.

Stateful packet filtering Stateful packet filtering also looks at each packet, but it can examine the packet in its relation to other packets. Stateful firewalls keep track of network connections and can apply slightly different rule sets based on whether the packet is part of an established session or not.

NAT is the process of modifying network address information in datagram packet headers while in transit across a traffic routing device, such as a router or firewall, for the purpose of remapping a given address space into another. See Chapter 9 for a more detailed discussion on NAT.

Access control lists (ACLs) ACLs are simple rule sets that are applied to port numbers and IP addresses. They can be configured for inbound and outbound traffic and are most commonly used on routers and switches.

Application layer proxies An application layer proxy can examine the content of the traffic as well as the ports and IP addresses. For example, an application layer has the ability to look inside a user’s web traffic, detect a malicious web site attempting to download malware to the user’s system, and block the malware.

One of the most basic security functions provided by a firewall is NAT. This service allows you to mask significant amounts of information from outside of the network. This allows an outside entity to communicate with an entity inside the firewall without truly knowing its address. Basic packet filtering, also known as stateless packet inspection,

involves looking at packets, their protocols and destinations, and checking that information against the security policy. Telnet and FTP connections may be prohibited from being established to a mail or database server, but they may be allowed for the respective service servers. This is a fairly simple method of filtering based on information in each packet header, like IP addresses and TCP/UDP ports. This will not detect and catch all undesired packets, but it is fast and efficient. To look at all packets, determining the need for each and its data,

requires stateful packet filtering. Advanced firewalls employ stateful packet filtering to prevent several types of undesired communications. Should a packet come from outside the network, in an attempt to pretend that it is a response to a message from inside the network, the firewall will

have no record of it being requested and can discard it, blocking access. As many communications will be transferred to high ports (above 1023), stateful monitoring will enable the system to determine which sets of high- port communications are permissible and which should be blocked. The disadvantage to stateful monitoring is that it takes significant resources and processing to do this type of monitoring, and this reduces efficiency and requires more robust and expensive hardware. However, this type of monitoring is essential in today’s comprehensive networks, particularly given the variety of remotely accessible services.

Tech Tip

Firewalls and Access Control Lists Many firewalls read firewall and ACL rules from top to bottom and apply the rules in sequential order to the packets they are inspecting. Typically they will stop processing rules when they find a rule that matches the packet they are examining. If the first line in your rule set reads “allow all traffic,” then the firewall will pass any network traffic coming into or leaving the firewall—ignoring the rest of your rules below that line. Many firewalls have an implied “deny all” line as part of their rule sets. This means that any traffic that is not specifically allowed by a rule will get blocked by default.

As they are in routers, switches, servers, and other network devices, ACLs are a cornerstone of security in firewalls. Just as you must protect the device from physical access, ACLs do the same task for electronic access. Firewalls can extend the concept of ACLs by enforcing them at a packet level when packet-level stateful filtering is performed. This can add an extra layer of protection, making it more difficult for an outside hacker to breach a firewall.

Exam Tip: Many firewalls contain, by default, an implicit deny at the end of every ACL or firewall rule set. This simply means that any traffic not specifically permitted by a previous rule

in the rule set is denied.

Some high-security firewalls also employ application layer proxies. As the name implies, packets are not allowed to traverse the firewall, but data instead flows up to an application that in turn decides what to do with it. For example, an SMTP proxy may accept inbound mail from the Internet and forward it to the internal corporate mail server, as depicted in Figure 10.6. While proxies provide a high level of security by making it very difficult for an attacker to manipulate the actual packets arriving at the destination, and while they provide the opportunity for an application to interpret the data prior to forwarding it to the destination, they generally are not capable of the same throughput as stateful packet-inspection firewalls. The trade-off between performance and speed is a common one and must be evaluated with respect to security needs and performance requirements.

• Figure 10.6 Firewall with SMTP application layer proxy

Tech Tip

Firewall Operations Application layer firewalls such as proxy servers can analyze information in the header and data portion of the packet, whereas packet-filtering firewalls can analyze only the header of a

packet.

Firewalls can also act as network traffic regulators in that they can be configured to mitigate specific types of network-based attacks. In denial- of-service and distributed denial-of-service attacks, an attacker can attempt to flood a network with traffic. Firewalls can be tuned to detect these types of attacks and act as flood guards, mitigating the effect on the network.

Exam Tip: Firewalls can act as flood guards, detecting and mitigating specific types of DoS/DDoS attacks.

Next-Generation Firewalls Firewalls operate by inspecting packets and by using rules associated with IP addresses and ports. Next-generation firewalls have significantly more capability and are characterized by these features:

Deep packet inspection

Move beyond port/protocol inspection and blocking

Add application-level inspection

Add intrusion prevention

Bring intelligence from outside the firewall

Next-generation firewalls are more than just a firewall and IDS coupled together; they offer a deeper look at what the network traffic represents. In a legacy firewall, with port 80 open, all web traffic is allowed to pass. Using a next-generation firewall, traffic over port 80 can be separated by web site, or even activity on a web site (for example, allow Facebook, but not games on Facebook). Because of the deeper packet inspection and the

ability to create rules based on content, traffic can be managed based on content, not merely site or URL.

Web Application Firewalls vs. Network Firewalls Increasingly, the term “firewall” is getting attached to any device or software package that is used to control the flow of packets or data into or out of an organization. For example, a web application firewall is the term given to any software package, appliance, or filter that applies a rule set to HTTP/HTTPS traffic. Web application firewalls shape web traffic and can be used to filter out SQL injection attacks, malware, cross-site scripting (XSS), and so on. By contrast, a network firewall is a hardware or software package that controls the flow of packets into and out of a network. Web application firewalls operate on traffic at a much higher level than network firewalls, as web application firewalls must be able to decode the web traffic to determine whether or not it is malicious. Network firewalls operate on much simpler aspects of network traffic such as source/destination port and source/destination address.

Concentrators Network devices called concentrators act as traffic management devices, managing flows from multiple points into single streams. Concentrators typically act as endpoints for a particular protocol, such as SSL/TLS or VPN. The use of specialized hardware can enable hardware-based encryption and provide a higher level of specific service than a general- purpose server. This provides both architectural and functional efficiencies.

Wireless Devices Wireless devices bring additional security concerns. There is, by definition, no physical connection to a wireless device; radio waves or

infrared carry data, which allows anyone within range access to the data. This means that unless you take specific precautions, you have no control over who can see your data. Placing a wireless device behind a firewall does not do any good, because the firewall stops only physically connected traffic from reaching the device. Outside traffic can come literally from the parking lot directly to the wireless device and into the network. The point of entry from a wireless device to a wired network is

performed at a device called a wireless access point. Wireless access points can support multiple concurrent devices accessing network resources through the network node they create. A typical wireless access point is shown here.

• A typical wireless access point

To prevent unauthorized wireless access to the network, configuration of remote access protocols to a wireless access point is common. Forcing authentication and verifying authorization is a seamless method of performing basic network security for connections in this fashion. These access protocols are covered in Chapter 11.

Several mechanisms can be used to add wireless functionality to a machine. For PCs, this can be done via an expansion card. For notebooks, a PCMCIA adapter for wireless networks is available from several vendors. For both PCs and notebooks, vendors have introduced USB- based wireless connectors. The following illustration shows one vendor’s card—note the extended length used as an antenna. Not all cards have the same configuration, although they all perform the same function: to enable a wireless network connection. The numerous wireless protocols (802.11a, b, g, i, and n) are covered in Chapter 12. Wireless access points and cards must be matched by protocol for proper operation.

Modems Modems were once a slow method of remote connection that was used to connect client workstations to remote services over standard telephone lines. Modem is a shortened form of modulator/demodulator, converting analog signals to digital and vice versa. Connecting a digital computer signal to the analog telephone line required one of these devices. Today, the use of the term has expanded to cover devices connected to special digital telephone lines—DSL modems—and to cable television lines— cable modems. Although these devices are not actually modems in the true sense of the word, the term has stuck through marketing efforts directed to consumers. DSL and cable modems offer broadband high-speed connections and the opportunity for continuous connections to the Internet. Along with these new desirable characteristics come some undesirable ones, however. Although they both provide the same type of service, cable and DSL modems have some differences. A DSL modem provides a direct

connection between a subscriber’s computer and an Internet connection at the local telephone company’s switching station. This private connection offers a degree of security, as it does not involve others sharing the circuit. Cable modems are set up in shared arrangements that theoretically could allow a neighbor to sniff a user’s cable modem traffic.

• A typical PCMCIA wireless network card

Cable modems were designed to share a party line in the terminal signal area, and the cable modem standard, Data Over Cable Service Interface Specification (DOCSIS), was designed to accommodate this concept. DOCSIS includes built-in support for security protocols, including

authentication and packet filtering. Although this does not guarantee privacy, it prevents ordinary subscribers from seeing others’ traffic without using specialized hardware. Figure 10.7 is a modern cable modem. It has an imbedded wireless

access point, a VoIP connection, a local router, and DHCP server. The size of the device is fairly large, but it has a built-in lead-acid battery to provide VoIP service when power is out.

• Figure 10.7 Modern cable modem

Both cable and DSL services are designed for a continuous connection, which brings up the question of IP address life for a client. Although some services originally used a static IP arrangement, virtually all have now adopted the Dynamic Host Configuration Protocol (DHCP) to manage their address space. A static IP address has an advantage of remaining the same and enabling convenient DNS connections for outside users. As cable and DSL services are primarily designed for client services as opposed to host services, this is not a relevant issue. A security issue of a static IP address is that it is a stationary target for hackers. The move to DHCP has not significantly lessened this threat, however, because the typical IP lease on a cable modem DHCP server is for days. This is still relatively stationary, and some form of firewall protection needs to be employed by the user.

Cable/DSL Security The modem equipment provided by the subscription service converts the cable or DSL signal into a standard Ethernet signal that can then be connected to a NIC on the client device. This is still just a direct network connection, with no security device separating the two. The most common security device used in cable/DSL connections is a router that acts as a hardware firewall. The firewall/router needs to be installed between the cable/DSL modem and client computers.

Telephony A private branch exchange (PBX) is an extension of the public telephone network into a business. Although typically considered separate entities from data systems, PBXs are frequently interconnected and have security requirements as part of this interconnection, as well as security requirements of their own. PBXs are computer-based switching equipment

designed to connect telephones into the local phone system. Basically digital switching systems, they can be compromised from the outside and used by phone hackers (phreakers) to make phone calls at the business’s expense. Although this type of hacking has decreased as the cost of long- distance calling has decreased, it has not gone away, and as several firms learn every year, voice mail boxes and PBXs can be compromised and the long-distance bills can get very high, very fast.

Tech Tip

Coexisting Communications Data and voice communications have coexisted in enterprises for decades. Recent connections inside the enterprise of Voice over IP (VoIP) and traditional private branch exchange (PBX) solutions increase both functionality and security risks. Specific firewalls to protect against unauthorized traffic over telephony connections are available to counter the increased risk.

Another problem with PBXs arises when they are interconnected to the data systems, either by corporate connection or by rogue modems in the hands of users. In either case, a path exists for connection to outside data networks and the Internet. Just as a firewall is needed for security on data connections, one is needed for these connections as well. Telecommunications firewalls are a distinct type of firewall designed to protect both the PBX and the data connections. The functionality of a telecommunications firewall is the same as that of a data firewall: it is there to enforce security policies. Telecommunication security policies can be enforced even to cover hours of phone use, to prevent unauthorized long-distance usage through the implementation of access codes and/or restricted service hours.

VPN Concentrator A virtual private network (VPN) is a construct used to provide a secure

communication channel between users across public networks such as the Internet. The most common implementation of VPN is via IPsec, a protocol for IP security. IPsec is mandated in IPv6 and is optional in IPv4. IPsec can be implemented in hardware, software, or a combination of both and is used to encrypt all IP traffic. In Chapter 11, a variety of techniques are described that can be employed to instantiate a VPN connection. The use of encryption technologies allows either the data in a packet to be encrypted or the entire packet to be encrypted. If the data is encrypted, the packet header can still be sniffed and observed between source and destination, but the encryption protects the contents of the packet from inspection. If the entire packet is encrypted, it is then placed into another packet and sent via tunnel across the public network. Tunneling can protect even the identity of the communicating parties.

Exam Tip: A VPN concentrator is a hardware device designed to act as a VPN endpoint, managing VPN connections to an enterprise.

Security Devices There are a range of security devices that can be employed at the network layer to instantiate security functionality in the network layer. Devices can be used for intrusion detection, network access control, and a wide range of other security functions. Each device has a specific network function and plays a role in maintaining network infrastructure security.

Intrusion Detection Systems Intrusion detection systems (IDSs) are an important element of infrastructure security. IDSs are designed to detect, log, and respond to unauthorized network or host use, both in real time and after the fact. IDSs

are available from a wide selection of vendors and are an essential part of a comprehensive network security program. These systems are implemented using software, but in large networks or systems with significant traffic levels, dedicated hardware is typically required as well. IDSs can be divided into two categories: network-based systems and host-based systems.

Cross Check Intrusion Detection From a network infrastructure point of view, network-based IDSs can be considered part of infrastructure, whereas host-based IDSs are typically considered part of a comprehensive security program and not necessarily infrastructure. Two primary methods of detection are used: signature-based and anomaly-based. IDSs are covered in detail in Chapter 13.

Network Access Control Networks comprise connected workstations and servers. Managing security on a network involves managing a wide range of issues, from various connected hardware and the software operating these devices. Assuming that the network is secure, each additional connection involves risk. Managing the endpoints on a case-by-case basis as they connect is a security methodology known as network access control. Two main competing methodologies exist that deal with network access control: Network Access Protection (NAP) is a Microsoft technology for controlling network access of a computer host, and Network Admission Control (NAC) is Cisco’s technology for controlling network admission.

Tech Tip

NAC and NAP Interoperability Although Microsoft’s NAP and Cisco’s NAC appear to be competing methodologies, they are

in fact complementary. NAP allows much finer-grain control for Windows-based devices, while NAC is a more general-purpose methodology for controlling admission through edge devices. Recognizing how they can work together, Microsoft and Cisco have deployed guides on how to combine these two systems, preserving the advantages and investments in each.

Microsoft’s NAP system is based on measuring the system health of the connecting machine, including patch levels of the OS, antivirus protection, and system policies. The objective behind NAP is to enforce policy and governance standards on network devices before they are allowed data- level access to a network. NAP was first utilized in Windows XP Service Pack 3, Windows Vista, and Windows Server 2008, and it requires additional infrastructure servers to implement the health checks. The system includes enforcement agents that interrogate clients and verify admission criteria. Admission criteria can include client machine ID, status of updates, and so forth. Using NAP, network administrators can define granular levels of network access based on multiple criteria; who a client is, what groups a client belongs to, and the degree to which that client is compliant with corporate client health requirements. These health requirements include OS updates, antivirus updates, and critical patches. Response options include rejection of the connection request or restriction of admission to a subnet. NAP also provides a mechanism for automatic remediation of client health requirements and restoration of normal access when healthy. Cisco’s NAC system is built around an appliance that enforces policies

chosen by the network administrator. A series of third-party solutions can interface with the appliance, allowing the verification of many different options, including client policy settings, software updates, and client security posture. The use of third-party devices and software makes this an extensible system across a wide range of equipment. Both Cisco NAC and Microsoft NAP are in their early stages of

widespread implementation, with only large enterprises typically taking these steps. Although they have been available for over 5 years, they are not being embraced across most firms. The concept of automated admission checking based on client device characteristics is here to stay, as

it provides timely control in the ever-changing network world of today’s enterprises.

Network Monitoring/Diagnostic A computer network itself can be considered a large computer system, with performance and operating issues. Just as a computer needs management, monitoring, and fault resolution, so do networks. SNMP was developed to perform this function across networks. The idea is to enable a central monitoring and control center to maintain, configure, and repair network devices, such as switches and routers, as well as other network services, such as firewalls, IDSs, and remote access servers. SNMP has some security limitations, and many vendors have developed software solutions that sit on top of SNMP to provide better security and better management tool suites.

SNMP, Simple Network Management Protocol, is a part of the Internet Protocol suite of protocols. It is an open standard, designed for transmission of management functions between devices. Do not confuse this with SMTP, Simple Mail Transfer Protocol, which is used to transfer mail between machines.

The concept of a network operations center (NOC) comes from the old phone company network days, when central monitoring centers monitored the health of the telephone network and provided interfaces for maintenance and management. This same concept works well with computer networks, and companies with midsize and larger networks employ the same philosophy. The NOC allows operators to observe and interact with the network, using the self-reporting and, in some cases, self- healing nature of network devices to ensure efficient network operation. Although generally a boring operation under normal conditions, when things start to go wrong, as in the case of a virus or worm attack, the NOC

can become a busy and stressful place as operators attempt to return the system to full efficiency while not interrupting existing traffic. As networks can be spread out literally around the world, it is not

feasible to have a person visit each device for control functions. Software enables controllers at NOCs to measure the actual performance of network devices and make changes to the configuration and operation of devices remotely. The ability to make remote connections with this level of functionality is both a blessing and a security issue. Although this allows efficient network operations management, it also provides an opportunity for unauthorized entry into a network. For this reason, a variety of security controls are used, from secondary networks to VPNs and advanced authentication methods with respect to network control connections. Network monitoring is an ongoing concern for any significant network.

In addition to monitoring traffic flow and efficiency, monitoring of security-related events is necessary. IDSs act merely as alarms, indicating the possibility of a breach associated with a specific set of activities. These indications still need to be investigated and an appropriate response needs to be initiated by security personnel. Simple items such as port scans may be ignored by policy, but an actual unauthorized entry into a network router, for instance, would require NOC personnel to take specific actions to limit the potential damage to the system. In any significant network, coordinating system changes, dynamic network traffic levels, potential security incidents, and maintenance activities is a daunting task requiring numerous personnel working together. Software has been developed to help manage the information flow required to support these tasks. Such software can enable remote administration of devices in a standard fashion, so that the control systems can be devised in a hardware vendor– neutral configuration. SNMP is the main standard embraced by vendors to permit

interoperability. Although SNMP has received a lot of security-related attention of late due to various security holes in its implementation, it is still an important part of a security solution associated with network infrastructure. Many useful tools have security issues; the key is to

understand the limitations and to use the tools within correct boundaries to limit the risk associated with the vulnerabilities. Blind use of any technology will result in increased risk, and SNMP is no exception. Proper planning, setup, and deployment can limit exposure to vulnerabilities. Continuous auditing and maintenance of systems with the latest patches is a necessary part of operations and is essential to maintaining a secure posture.

Load Balancers Certain systems, such as servers, are more critical to business operations and should therefore be the object of fault-tolerance measures. Load balancers are designed to distribute the processing load over two or more systems. They are used to help improve resource utilization and throughput but also have the added advantage of increasing the fault tolerance of the overall system since a critical process may be split across several systems. Should any one system fail, the others can pick up the processing it was handling.

Proxies Proxies serve to manage connections between systems, acting as relays for the traffic. Proxies can function at the circuit level, where they support multiple traffic types, or they can be application-level proxies, which are designed to relay specific application traffic. An HTTP proxy can manage an HTTP conversation as it understands the type and function of the content. Application-specific proxies can serve as security devices if they are programmed with specific rules designed to provide protection against undesired content. Though not strictly a security tool, a proxy server (or simply proxy) can

be used to filter out undesirable traffic and prevent employees from accessing potentially hostile web sites. A proxy server takes requests from a client system and forwards them to the destination server on behalf of the

client, as shown in Figure 10.8. Proxy servers can be completely transparent (these are usually called gateways or tunneling proxies), or a proxy server can modify the client request before sending it on, or even serve the client’s request without needing to contact the destination server. Several major categories of proxy servers are in use:

• Figure 10.8 HTTP proxy handling client requests and web server responses

Anonymizing proxy An anonymizing proxy is designed to hide information about the requesting system and make a user’s web browsing experience “anonymous.” This type of proxy service is often

used by individuals who are concerned about the amount of personal information being transferred across the Internet and the use of tracking cookies and other mechanisms to track browsing activity.

Caching proxy This type of proxy keeps local copies of popular client requests and is often used in large organizations to reduce bandwidth usage and increase performance. When a request is made, the proxy server first checks to see whether it has a current copy of the requested content in the cache; if it does, it services the client request immediately without having to contact the destination server. If the content is old or the caching proxy does not have a copy of the requested content, the request is forwarded to the destination server.

Content-filtering proxy Content-filtering proxies examine each client request and compare it to an established acceptable use policy (AUP). Requests can usually be filtered in a variety of ways, including by the requested URL, destination system, or domain name or by keywords in the content itself. Content-filtering proxies typically support user-level authentication, so access can be controlled and monitored and activity through the proxy can be logged and analyzed. This type of proxy is very popular in schools, corporate environments, and government networks.

Open proxy An open proxy is essentially a proxy that is available to any Internet user and often has some anonymizing capabilities as well. This type of proxy has been the subject of some controversy, with advocates for Internet privacy and freedom on one side of the argument, and law enforcement, corporations, and government entities on the other side. As open proxies are often used to circumvent corporate proxies, many corporations attempt to block the use of open proxies by their employees.

Reverse proxy A reverse proxy is typically installed on the server side of a network connection, often in front of a group of web servers. The reverse proxy intercepts all incoming web requests and can perform a number of functions, including traffic filtering and shaping, SSL

decryption, serving of common static content such as graphics, and performing load balancing.

Web proxy A web proxy is solely designed to handle web traffic and is sometimes called a web cache. Most web proxies are essentially specialized caching proxies.

Exam Tip: A proxy server is a system or application that acts as a go-between for clients’ requests for network services. The client tells the proxy server what it wants and, if the client is authorized to have it, the proxy server connects to the appropriate network service and gets the client what it asked for. Web proxies are the most commonly deployed type of proxy server.

Deploying a proxy solution within a network environment is usually done either by setting up the proxy and requiring all client systems to configure their browsers to use the proxy or by deploying an intercepting proxy that actively intercepts all requests without requiring client-side configuration. From a security perspective, proxies are most useful in their ability to

control and filter outbound requests. By limiting the types of content and web sites employees can access from corporate systems, many administrators hope to avoid loss of corporate data, hijacked systems, and infections from malicious web sites. Administrators also use proxies to enforce corporate AUPs and track use of corporate resources. Most proxies can be configured to either allow or require individual user authentication —this gives them the ability to log and control activity based on specific users or groups. For example, an organization might want to allow the human resources group to browse Facebook during business hours but not allow the rest of the organization to do so.

Web Security Gateways Some security vendors combine proxy functions with content-filtering

functions to create a product called a web security gateway. Web security gateways are intended to address the security threats and pitfalls unique to web-based traffic. Web security gateways typically provide the following capabilities:

Real-time malware protection (a.k.a. malware inspection) The ability to scan all outgoing and incoming web traffic to detect and block undesirable traffic such as malware, spyware, adware, malicious scripts, file-based attacks, and so on.

Content monitoring The ability to monitor the content of web traffic being examined to ensure that it complies with organizational policies.

Productivity monitoring The ability to measure types and quantities of web traffic that is being generated by specific users, groups of users, or the entire organization.

Data protection and compliance Scanning web traffic for sensitive or proprietary information being sent outside of the organization as well as the use of social network sites or inappropriate sites.

Internet Content Filters With the dramatic proliferation of Internet traffic and the push to provide Internet access to every desktop, many corporations have implemented content-filtering systems, called an Internet content filter, to protect them from employees’ viewing of inappropriate or illegal content at the workplace and the subsequent complications that occur when such viewing takes place. Internet content filtering is also popular in schools, libraries, homes, government offices, and any other environment where there is a need to limit or restrict access to undesirable content. In addition to filtering undesirable content, such as pornography, some content filters can also filter out malicious activity such as browser hijacking attempts or XSS attacks. In many cases, content filtering is performed with or as a part of a proxy solution as the content requests can be filtered and serviced by

the same device. Content can be filtered in a variety of ways, including via the requested URL, the destination system, the domain name, by keywords in the content itself, and by type of file requested.

The term “Internet content filter” or “content filter” is applied to any device, application, or software package that examines network traffic (especially web traffic) for undesirable or restricted content. A content filter could be a software package loaded on a specific PC or a network appliance capable of filtering an entire organization’s web traffic.

Content-filtering systems face many challenges, because the ever- changing Internet makes it difficult to maintain lists of undesirable sites (sometime called black lists); terms used on a medical site can also be used on a pornographic site, making keyword filtering challenging; and determined users are always seeking ways to bypass proxy filters. To help administrators, most commercial content-filtering solutions provide an update service, much like IDS or antivirus products that updates keywords and undesirable sites automatically.

Data Loss Prevention Data loss prevention (DLP) refers to technology employed to detect and prevent transfers of data across an enterprise. Employed at key locations, DLP technology can scan packets for specific data patterns. This technology can be tuned to detect account numbers, secrets, specific markers, or files. When specific data elements are detected, the system can block the transfer. The primary challenge in employing DLP technologies is the placement of the sensor. The DLP sensor needs to be able observe the data, so if the channel is encrypted, DLP technology can be thwarted.

Unified Threat Management Many security vendors offer “all-in-one security appliances,” which are

devices that combine multiple functions into the same hardware appliance. Most commonly these functions are firewall, IDS/IPS, and antivirus, although all-in-one appliances can include VPN capabilities, antispam, malicious web traffic filtering, antispyware, content filtering, traffic shaping, and so on. All-in-one appliances are often sold as being cheaper, easier to manage, and more efficient than having separate solutions that accomplish each of the functions the all-in-one appliance is capable of performing. A common name for these all-in-one appliances is a unified threat management (UTM) appliance. Using a UTM solution simplifies the security activity as a single task, under a common software package for operations. This reduces the learning curve to a single tool rather than a collection of tools. A UTM solution can have better integration and efficiencies in handling network traffic and incidents than a collection of tools connected together. Figure 10.9 illustrates the advantages of UTM processing. Rather than

processing elements in a linear fashion, as shown in 10.9a, the packets are processed in a parallelized fashion (b). There is a need to coordinate between the elements and many modern solutions do this with parallelized hardware.

• Figure 10.9 Unified threat management architecture

URL Filtering URL filters block connections to web sites that are in a prohibited list. The use of a UTM appliance, typically backed by a service to keep the list of prohibited web sites updated, provides an automated means to block access to sites deemed dangerous or inappropriate. Because of the highly volatile nature of web content, automated enterprise-level protection is needed to ensure a reasonable chance of blocking sources of inappropriate

content, malware, and other malicious content.

Content Inspection Instead of just relying on a URL to determine the acceptability of content, UTM appliances can also inspect the actual content being served. Content inspection is used to filter web requests that return content with specific components, such as names of body parts, music or video content, and other content that is inappropriate for the business environment.

Malware Inspection Malware is another item that can be detected during network transmission, and UTM appliances can be tuned to detect malware. Network-based malware detection has the advantage of having to update only a single system as opposed to all machines.

Media The base of communications between devices is the physical layer of the OSI model. This is the domain of the actual connection between devices, whether by wire, fiber, or radio frequency waves. The physical layer separates the definitions and protocols required to transmit the signal physically between boxes from higher-level protocols that deal with the details of the data itself. Four common methods are used to connect equipment at the physical layer:

Coaxial cable

Twisted-pair cable

Fiber-optics

Wireless

Coaxial Cable Coaxial cable is familiar to many households as a method of connecting televisions to VCRs or to satellite or cable services. It is used because of its high bandwidth and shielding capabilities. Compared to standard twisted-pair lines such as telephone lines, coaxial cable (“coax”) is much less prone to outside interference. It is also much more expensive to run, both from a cost-per-foot measure and from a cable-dimension measure. Coax costs much more per foot than standard twisted-pair wires and carries only a single circuit for a large wire diameter.

• A coax connector

An original design specification for Ethernet connections, coax was used from machine to machine in early Ethernet implementations. The connectors were easy to use and ensured good connections, and the limited distance of most office LANs did not carry a large cost penalty. Today, almost all of this older Ethernet specification has been replaced by faster, cheaper twisted-pair alternatives, and the only place you’re likely to see coax in a data network is from the cable box to the cable modem.

• A typical 8-wire UTP line

Because of its physical nature, it is possible to drill a hole through the outer part of a coax cable and connect to the center connector. This is called a “vampire tap” and is an easy method to get access to the signal and data being transmitted.

UTP/STP Twisted-pair wires have all but completely replaced coaxial cables in Ethernet networks. Twisted-pair wires use the same technology used by the phone company for the movement of electrical signals. Single pairs of twisted wires reduce electrical crosstalk and electromagnetic interference. Multiple groups of twisted pairs can then be bundled together in common groups and easily wired between devices.

• A typical 8-wire STP line

• A bundle of UTP wires

Twisted pairs come in two types, shielded and unshielded. Shielded twisted-pair (STP) has a foil shield around the pairs to provide extra shielding from electromagnetic interference. Unshielded twisted-pair (UTP) relies on the twist to eliminate interference. UTP has a cost advantage over STP and is usually sufficient for connections, except in very noisy electrical areas.

Twisted-pair lines are categorized by the level of data transmission they can support. Three current categories are in use:

Category 3 (Cat 3) Minimum for voice and 10-Mbps Ethernet. Category 5 (Cat 5/Cat 5e) For 100-Mbps Fast Ethernet; Cat 5e is an enhanced version of the Cat 5 specification to address far-end crosstalk and is suitable for 1000 Mbps.

Category 6 (Cat 6/Cat 6a) For 10-Gigabit Ethernet over short distances; Cat 6a is used for longer, up to 100m, 10-Gbps cables.

The standard method for connecting twisted-pair cables is via an 8-pin connector, called an RJ-45 connector that looks like a standard phone jack connector but is slightly larger. One nice aspect of twisted-pair cabling is that it’s easy to splice and change connectors. Many a network administrator has made Ethernet cables from stock Cat-5 wire, two connectors, and a crimping tool. This ease of connection is also a security issue; because twisted-pair cables are easy to splice into, rogue connections for sniffing could be made without detection in cable runs. Both coax and fiber are much more difficult to splice because each requires a tap to connect, and taps are easier to detect.

Fiber Fiber-optic cable uses beams of laser light to connect devices over a thin glass wire. The biggest advantage to fiber is its bandwidth, with transmission capabilities into the terabits per second range. Fiber-optic cable is used to make high-speed connections between servers and is the backbone medium of the Internet and large networks. For all of its speed and bandwidth advantages, fiber has one major drawback—cost. The cost of using fiber is a two-edged sword. When measured by

bandwidth, using fiber is cheaper than using competing wired technologies. The length of runs of fiber can be much longer, and the data capacity of fiber is much higher. But connections to a fiber are difficult

and expensive, and fiber is impossible to splice. Making the precise connection on the end of a fiber-optic line is a highly skilled job and is done by specially trained professionals who maintain a level of proficiency. Once the connector is fitted on the end, several forms of connectors and blocks are used, as shown in the images above.

• A type of fiber terminator

• A typical fiber-optic fiber, terminator, and connector block

Splicing fiber is practically impossible; the solution is to add connectors and connect through a repeater. This adds to the security of fiber in that unauthorized connections are all but impossible to make. The high cost of connections to fiber and the higher cost of fiber per foot also make it less attractive for the final mile in public networks where users are connected to the public switching systems. For this reason, cable companies use coax and DSL providers use twisted-pair to handle the “last mile” scenario.

Unguided Media

Electromagnetic waves have been transmitted to convey signals literally since the inception of radio. Unguided media is a phrase used to cover all transmission media not guided by wire, fiber, or other constraints; it includes radio frequency, infrared, and microwave methods. Unguided media have one attribute in common: they are unguided and as such can travel to many machines simultaneously. Transmission patterns can be modulated by antennas, but the target machine can be one of many in a reception zone. As such, security principles are even more critical, as they must assume that unauthorized users have access to the signal.

Infrared Infrared (IR) is a band of electromagnetic energy just beyond the red end of the visible color spectrum. IR has been used in remote-control devices for years. IR made its debut in computer networking as a wireless method to connect to printers. Now that wireless keyboards, wireless mice, and mobile devices exchange data via IR, it seems to be everywhere. IR can also be used to connect devices in a network configuration, but it is slow compared to other wireless technologies. IR cannot penetrate walls but instead bounces off them. Nor can it penetrate other solid objects, so if you stack a few items in front of the transceiver, the signal is lost.

RF/Microwave The use of radio frequency (RF) waves to carry communication signals goes back to the beginning of the 20th century. RF waves are a common method of communicating in a wireless world. They use a variety of frequency bands, each with special characteristics. The term microwave is used to describe a specific portion of the RF spectrum that is used for communication and other tasks, such as cooking. Point-to-point microwave links have been installed by many network

providers to carry communications over long distances and rough terrain. Many different frequencies are used in the microwave bands for many different purposes. Today, home users can use wireless networking throughout their house and enable laptops to surf the Web while they’re

moved around the house. Corporate users are experiencing the same phenomenon, with wireless networking enabling corporate users to check e-mail on laptops while riding a shuttle bus on a business campus. These wireless solutions are covered in detail in Chapter 12.

Tech Tip

Wireless Options There are numerous radio-based alternatives for carrying network traffic. They vary in capacity, distance, and other features. Commonly found examples are WiFi, WiMAX, ZigBee, Bluetooth, 900 MHz, and NFC. Understanding the security requirements associated with each is important and is covered in more detail in Chapter 12.

One key feature of microwave communications is that microwave RF energy can penetrate reasonable amounts of building structure. This allows you to connect network devices in separate rooms, and it can remove the constraints on equipment location imposed by fixed wiring. Another key feature is broadcast capability. By its nature, RF energy is unguided and can be received by multiple users simultaneously. Microwaves allow multiple users access in a limited area, and microwave systems are seeing application as the last mile of the Internet in dense metropolitan areas. Point-to-multipoint microwave devices can deliver data communication to all the business users in a downtown metropolitan area through rooftop antennas, reducing the need for expensive building-to-building cables. Just as microwaves carry cell phone and other data communications, the same technologies offer a method to bridge the last-mile solution. The “last mile” problem is the connection of individual consumers to a

backbone, an expensive proposition because of the sheer number of connections and unshared line at this point in a network. Again, cost is an issue, as transceiver equipment is expensive, but in densely populated areas, such as apartments and office buildings in metropolitan areas, the user density can help defray individual costs. Speed on commercial microwave links can exceed 10 Gbps, so speed is not a problem for

connecting multiple users or for high-bandwidth applications.

Removable Media One concept common to all computer users is data storage. Sometimes storage occurs on a file server and sometimes it occurs on movable media, allowing it to be transported between machines. Moving storage media represents a security risk from a couple of angles, the first being the potential loss of control over the data on the moving media. Second is the risk of introducing unwanted items, such as a virus or a worm, when the media are attached back to a network. Both of these issues can be remedied through policies and software. The key is to ensure that the policies are enforced and the software is effective. To describe media- specific issues, media can be divided into three categories: magnetic, optical, and electronic.

Removable and transportable media make the physical security of the data a more difficult task. The only solution to this problem is encryption, which is covered in Chapter 5.

Magnetic Media Magnetic media store data through the rearrangement of magnetic particles on a nonmagnetic substrate. Common forms include hard drives, floppy disks, zip disks, and magnetic tape. Although the specific format can differ, the basic concept is the same. All these devices share some common characteristics: Each has sensitivity to external magnetic fields. Attach a floppy disk to the refrigerator door with a magnet if you want to test the sensitivity. They are also affected by high temperatures, as in fires, and by exposure to water.

Hard Drives Hard drives used to require large machines in mainframes. Now they are small enough to attach to mobile devices. The concepts remain the same among all of them: a spinning platter rotates the magnetic media beneath heads that read the patterns in the oxide coating. As drives have gotten smaller and rotation speeds have increased, the capacities have also grown. Today gigabytes of data can be stored in a device slightly larger than a bottle cap. Portable hard drives in the 1TB to 3TB range are now available and affordable.

• 2TB USB hard drive

One of the security controls available to help protect the confidentiality of the data is full drive encryption built into the drive hardware. Using a key that is controlled, through a Trusted Platform Module (TPM) interface

for instance, this technology protects the data if the drive itself is lost or stolen. This may not be important if a thief takes the whole PC, but in larger storage environments, drives are placed in separate boxes and remotely accessed. In the specific case of notebook machines, this layer can be tied to smart card interfaces to provide more security. As this is built into the controller, encryption protocols such as Advanced Encryption Standard (AES) and Triple Data Encryption Standard (3DES) can be performed at full drive speed.

Diskettes Floppy disks were the computer industry’s first attempt at portable magnetic media. The movable medium was placed in a protective sleeve, and the drive remained in the machine. Capacities up to 1.4MB were achieved, but the fragility of the device as the size increased, as well as competing media, has rendered floppies almost obsolete. Diskettes are part of history now.

Tape Magnetic tape has held a place in computer centers since the beginning of computing. Its primary use has been bulk offline storage and backup. Tape functions well in this role because of its low cost. The disadvantage of tape is its nature as a serial access medium, making it slow to work with for large quantities of data. Several types of magnetic tape are in use today, ranging from quarter inch to digital linear tape (DLT) and digital audio tape (DAT). These cartridges can hold upward of 60GB of compressed data. Tapes are still a major concern from a security perspective, as they are

used to back up many types of computer systems. The physical protection afforded the tapes is of concern, because if a tape is stolen, an unauthorized user could establish a network and recover your data on his system, because it’s all stored on the tape. Offsite storage is needed for proper disaster recovery protection, but secure offsite storage and transport is what is really needed. This important issue is frequently overlooked in

many facilities. The simple solution to maintain control over the data even when you can’t control the tape is through encryption. Backup utilities can secure the backups with encryption, but this option is frequently not used, for a variety of reasons. Regardless of the rationale for not encrypting data, once a tape is lost, not using the encryption option becomes a lamented decision.

• A magnetic tape cartridge for backups

Optical Media Optical media involve the use of a laser to read data stored on a physical

device. Instead of having a magnetic head that picks up magnetic marks on a disk, a laser picks up deformities embedded in the media that contain the information. As with magnetic media, optical media can be read-write, although the read-only version is still more common.

CD-R/DVD The compact disc (CD) took the music industry by storm, and then it took the computer industry by storm as well. A standard CD holds more than 640MB of data, in some cases up to 800MB. The digital video disc (DVD) can hold almost 5GB of data single sided, 8.5GB dual layer. These devices operate as optical storage, with little marks burned in them to represent 1’s and 0’s on a microscopic scale. The most common type of CD is the read- only version, in which the data is written to the disc once and only read afterward. This has become a popular method for distributing computer software, although higher-capacity DVDs have replaced CDs for program distribution.

• A DVD (left) and CD (right)

A second-generation device, the recordable compact disc (CD-R), allows users to create their own CDs using a burner device in their PC and special software. Users can now back up data, make their own audio CDs, and use CDs as high-capacity storage. Their relatively low cost has made them economical to use. CDs have a thin layer of aluminum inside the plastic, upon which bumps are burned by the laser when recorded. CD-Rs use a reflective layer, such as gold, upon which a dye is placed that changes upon impact by the recording laser. A newer type, CD-RW, has a different dye that allows discs to be erased and reused. The cost of the media increases from CD, to CD-R, to CD-RW.

Blu-ray Discs The latest version of optical disc is the Blu-ray disc. Using a smaller, violet-blue laser, this system can hold significantly more information than a DVD. Blu-ray discs can hold up to 128GB in four layers. The transfer speed of Blu-ray at > 48 Mbps is over four times greater than that of DVD systems. Designed for high-definition (HD) video, Blu-ray offers significant storage for data as well.

Tech Tip

Backup Lifetimes A common misconception is that data backed up onto magnetic media will last for long periods of time. Although once touted as lasting decades, modern micro-encoding methods are proving less durable than expected, sometimes with lifetimes less than ten years. A secondary problem is maintaining operating system access via drivers to legacy equipment. As technology moves forward, finding drivers for ten-year-old tape drives for Windows 7 or the latest version of Linux will prove to be a major hurdle.

DVDs now occupy the same role that CDs have in the recent past, except that they hold more than seven times the data of a CD. This makes full-length movie recording possible on a single disc. The increased capacity comes from finer tolerances and the fact that DVDs can hold data

on both sides. A wide range of formats for DVDs include DVD+R, DVD- R, dual layer, and now HD formats, HD-DVD and Blu-ray. This variety is due to competing “standards” and can result in confusion. DVD+R and -R are distinguishable only when recording, and most devices since 2004 should read both. Dual layers add additional space but require appropriate dual-layer–enabled drives.

Electronic Media The latest form of removable media is electronic memory. Electronic circuits of static memory, which can retain data even without power, fill a niche where high density and small size are needed. Originally used in audio devices and digital cameras, these electronic media come in a variety of vendor-specific types, such as smart cards, SmartMedia, SD cards, flash cards, memory sticks, and CompactFlash devices. These memory devices range from small card-like devices, of which microSD cards are smaller than dimes and hold 2GB, to USB sticks that hold up to 64GB. These devices are becoming ubiquitous, with new PCs and netbooks containing built-in slots to read them like any other storage device.

• SD, microSD, and CompactFlash cards

Although they are used primarily for photos and music, these devices could be used to move any digital information from one machine to another. To a machine equipped with a connector port, these devices look like any other file storage location. They can be connected to a system through a special reader or directly via a USB port. In newer PC systems, a USB boot device has replaced the older floppy drive. These devices are small, can hold a significant amount of data—over 128GB at time of writing—and are easy to move from machine to machine. Another novel interface is a mouse that has a slot for a memory stick. This dual-purpose device conserves space, conserves USB ports, and is easy to use. The memory stick is placed in the mouse, which can then be used normally. The stick is easily removable and transportable. The mouse works with or without the memory stick; it is just a convenient device to use for a portal.

The advent of large-capacity USB sticks has enabled users to build entire systems, OSs, and tools onto them to ensure security and veracity of the OS and tools. With the expanding use of virtualization, a user could carry an entire system on a USB stick and boot it using virtually any hardware. With USB 3.0 and its 640-Mbps speeds, this is a highly versatile form of memory that enables many new capabilities.

• 128GB USB 3.0 memory stick

Solid-State Hard Drives With the rise of solid-state memory technologies comes a solid-state “hard drive.” Solid-state drives (SSDs) are moving into mobile devices, desktops, and even servers. Memory densities are significantly beyond physical drives, there are no moving parts to wear out or fail, and SSDs have vastly superior performance specifications. Figure 10.10 shows a 512GB SSD from a laptop, on a half-height minicard mSATA interface. The only factor that has slowed the spread of this technology has been cost, but recent cost reductions have made this form of memory a first

choice in many systems.

Figure 10.10 512GB solid-state half-height minicard

Security Concerns for Transmission Media The primary security concern for a system administrator has to be

preventing physical access to a server by an unauthorized individual. Such access will almost always spell disaster, for with direct access and the correct tools, any system can be infiltrated. One of the administrator’s next major concerns should be preventing unfettered access to a network connection. Access to switches and routers is almost as bad as direct access to a server, and access to network connections would rank third in terms of worst-case scenarios. Preventing such access is costly, yet the cost of replacing a server because of theft is also costly.

Physical Security Concerns A balanced approach is the most sensible approach when addressing physical security, and this applies to transmission media as well. Keeping network switch rooms secure and cable runs secure seems obvious, but cases of using janitorial closets for this vital business purpose abound. One of the keys to mounting a successful attack on a network is information. Usernames, passwords, server locations—all of these can be obtained if someone has the ability to observe network traffic in a process called sniffing. A sniffer can record all the network traffic, and this data can be mined for accounts, passwords, and traffic content, all of which can be useful to an unauthorized user. One starting point for many intrusions is the insertion of an unauthorized sniffer into the network, with the fruits of its labors driving the remaining unauthorized activities. Many common scenarios exist when unauthorized entry to a network occurs, including these:

Inserting a node and functionality that is not authorized on the network, such as a sniffer device or unauthorized wireless access point

Modifying firewall security policies

Modifying ACLs for firewalls, switches, or routers

Modifying network devices to echo traffic to an external node

Network devices and transmission media become targets because they are dispersed throughout an organization, and physical security of many dispersed items can be difficult to manage. Although limiting physical access is difficult, it is essential. The least level of skill is still more than sufficient to accomplish unauthorized entry into a network if physical access to the network signals is allowed. This is one factor driving many organizations to use fiber-optics, for these cables are much more difficult to tap. Although many tricks can be employed with switches and VLANs to increase security, it is still essential that you prevent unauthorized contact with the network equipment.

Cross Check Physical Infrastructure Security The best first effort is to secure the actual network equipment to prevent this type of intrusion. As you should remember from Chapter 8, physical access to network infrastructure provides a myriad of issues, and most of them can be catastrophic with respect to security. Physically securing access to network components is one of the “must dos” of a comprehensive security effort.

Wireless networks make the intruder’s task even easier, as they take the network to the users, authorized or not. A technique called war-driving involves using a laptop and software to find wireless networks from outside the premises. A typical use of war-driving is to locate a wireless network with poor (or no) security and obtain free Internet access, but other uses can be more devastating. A simple solution is to place a firewall between the wireless access point and the rest of the network and authenticate users before allowing entry. Business users use VPN technology to secure their connection to the Internet and other resources, and home users can do the same thing to prevent neighbors from “sharing” their Internet connections. To ensure that unauthorized traffic does not enter your network through a wireless access point, you must either use a firewall with an authentication system or establish a VPN.

Cloud Computing Cloud computing is a common term used to describe computer services provided over a network. These computing services are computing, storage, applications, and services that are offered via the Internet Protocol. One of the characteristics of cloud computing is transparency to the end user. This improves usability of this form of service provisioning. Cloud computing offers much to the user: improvements in performance, scalability, flexibility, security, and reliability, among other items. These improvements are a direct result of the specific attributes associated with how cloud services are implemented. Security is a particular challenge when data and computation are

handled by a remote party, as in cloud computing. The specific challenge is how does one allow data outside their enterprise and yet remain in control over how the data is used, and the common answer is encryption. By properly encrypting data before it leaves the enterprise, external storage can still be performed securely. Clouds can be created by many entities, internal and external to an

organization. Commercial cloud services are already available and offered by a variety of firms, as large as Google and Amazon, to smaller, local providers. Internal services can replicate the advantages of cloud computing while improving the utility of limited resources. The promise of cloud computing is improved utility and, as such, is marketed under the concepts of Software as a Service, Platform as a Service, and Infrastructure as a Service.

Private If your organization is highly sensitive to sharing resources, you may wish to consider the use of a private cloud. Private clouds are essentially reserved resources used only for your organization—your own little cloud within the cloud. This service will be considerably more expensive, but it should also carry less exposure and should enable your organization to

better define the security, processing, and handling of data that occurs within your cloud.

Public The term public cloud refers to when the cloud service is rendered over a system that is open for public use. In most cases, there is little operational difference between public and private cloud architectures, but the security ramifications can be substantial. Although public cloud services will separate users with security restrictions, the depth and level of these restrictions, by definition, will be significantly less in a public cloud.

Hybrid A hybrid cloud structure is one where elements are combined from private, public, and community cloud structures. When examining a hybrid structure, you need to remain cognizant that operationally these differing environments may not actually be joined, but rather used together. Sensitive information can be stored in the private cloud and issue-related information can be stored in the community cloud, all of which information is accessed by an application. This makes the overall system a hybrid cloud system.

Community A community cloud system is one where several organizations with a common interest share a cloud environment for the specific purposes of the shared endeavor. For example, local public entities and key local firms may share a community cloud dedicated to serving the interests of community initiatives. This can be an attractive cost-sharing mechanism for specific data-sharing initiatives.

Exam Tip: Be sure you understand the differences between cloud computing service models Platform as a Service, Software as a Service, and Infrastructure as a Service.

Software as a Service Software as a Service (SaaS) is the offering of software to end users from within the cloud. Rather than installing software on client machines, SaaS acts as software on demand where the software runs from the cloud. This has several advantages, as updates are often seamless to end users and integration between components is enhanced.

Platform as a Service Platform as a Service (PaaS) is a marketing term used to describe the offering of a computing platform in the cloud. Multiple sets of software, working together to provide services, such as database services, can be delivered via the cloud as a platform.

Infrastructure as a Service Infrastructure as a Service (IaaS) is a term used to describe cloud-based systems that are delivered as a virtual platform for computing. Rather than building data centers, IaaS allows firms to contract for utility computing as needed.

Chapter 10 Review

Lab Manual Exercise The following lab exercise from the companion lab manual, Principles of Computer Security Lab Manual, Fourth Edition, provides practical application of material covered in this chapter:

Lab 7.3l Configuring a Personal Firewall in Linux

Chapter Summary After reading this chapter and completing the exercises, you should understand the following aspects of networking and secure infrastructures.

Construct networks using different types of network devices

Understand the differences between basic network devices, such as hubs, bridges, switches, and routers.

Understand the security implications of network devices and how to construct a secure network infrastructure.

Enhance security using security devices

Understand the use of firewalls, next-generation firewalls, and intrusion detection systems.

Understand the role of load balancers and proxy servers as part of a secure network solution.

Understand the use of security appliances, such as web security gateways, data loss prevention, and unified threat management.

Enhance security using NAC/NAP methodologies

The Cisco NAC protocol and the Microsoft NAP protocol provide security functionality when attaching devices to a network.

NAC and NAP play a crucial role in the securing of infrastructure as devices enter and leave the network.

NAC and NAP can be used together to take advantage of the strengths and investments in each technology to form a strong network admission methodology.

Identify the different types of media used to carry network signals

Guided and unguided media can both carry network traffic.

Wired technology from coax cable, through twisted-pair Ethernet, provides a cost-effective means of carrying network traffic.

Fiber technology is used to carry higher bandwidth.

Unguided media, including infrared and RF (including wireless and Bluetooth), provide short-range network connectivity.

Describe the different types of storage media used to store information

There are a wide array of removable media types from memory sticks to optical discs to portable drives.

Data storage on removable media, because of increased physical access, creates significant security implications.

Use basic terminology associated with network functions related to information security

Understanding and using the correct vocabulary for device names and relationships to networking is important as a security professional.

Security appliances add terminology, including specific items for IDS and firewalls.

Describe the different types and uses of cloud computing

Understand the types of clouds in use.

Understand the use of Software as a Service, Infrastructure as a Service, and Platform as a Service.

Key Terms basic packet filtering (261) bridge (257) cloud computing (283) coaxial cable (274) collision domain (257) concentrator (264) data loss prevention (DLP) (272) firewall (260) hub (257) Infrastructure as a Service (IaaS) (284) Internet content filter (272) load balancer (269) modem (265) network access control (267) Network Access Protection (NAP) (267) Network Admission Control (NAC) (268) Network Attached Storage (NAS) (255) network interface card (NIC) (256) network operations center (NOC) (268) next-generation firewall (263) Platform as a Service (PaaS) (284) private branch exchange (PBX) (266) proxy server (270) router (258) sandboxing (255) servers (253)

shielded twisted-pair (STP) (275) Software as a Service (SaaS) (284) solid-state drive (SSD) (281) switch (257) unified threat management (UTM) (272) unshielded twisted-pair (UTP) (275) virtualization (254) web security gateway (271) wireless access point (264) workstation (253)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. A(n) _______________ routes packets based on IP addresses. 2. To offer software to end users from the cloud is a form of

_______________.

3. To connect a computer to a network, you use a(n) _______________.

4. A(n) _______________ or _______________ distributes traffic based on MAC addresses.

5. To verify that a computer is properly configured to connect to a network, the network can use _______________.

6. _______________ is a name for the typical computer a user uses on a network.

7. A(n) _______________ repeats all data traffic across all connected ports.

8. Cat 5 is an example of _______________ cable. 9. Basic packet filtering occurs at the ____________.

10. A(n) _______________ is an extension of the telephone service into a firm’s telecommunications network.

Multiple-Choice Quiz 1. Switches operate at which layer of the OSI model?

A. Physical layer

B. Network layer

C. Data link layer

D. Application layer

2. UTP cables are terminated for Ethernet using what type of connector?

A. A BNC plug

B. An Ethernet connector

C. A standard phone jack connector

D. An RJ-45 connector

3. Coaxial cable carries how many physical channels? A. Two

B. Four

C. One

D. None of the above

4. Network access control is associated with which of the following?

A. NAP

B. IPsec

C. IPv6

D. NAT

5. The purpose of twisting the wires in twisted-pair circuits is to: A. Increase speed

B. Increase bandwidth

C. Reduce crosstalk

D. Allow easier tracing

6. Microsoft NAP permits: A. Restriction of connections to a restricted subnet only

B. Checking of a client OS patch level before a network connection is permitted

C. Denial of a connection based on client policy settings

D. All of the above

7. SNMP is a protocol used for which of the following functions? A. Secure e-mail

B. Secure encryption of network packets

C. Remote access to user workstations

D. Remote access to network infrastructure

8. Firewalls can use which of the following in their operation? A. Stateful packet inspection

B. Port blocking to deny specific services

C. NAT to hide internal IP addresses

D. All of the above

9. SMTP is a protocol used for which of the following functions? A. E-mail

B. Secure encryption of network packets

C. Remote access to user workstations

D. None of the above

10. USB-based flash memory is characterized by: A. High cost

B. Low capacity

C. Slow access

D. None of the above

Essay Quiz 1. Compare and contrast routers and switches by describing what the

advantages and disadvantages are of each.

2. Describe the common threats to the transmission media in a network, by type of transmission media.

Lab Projects

• Lab Project 10.1 Using two PCs and a small home office–type router, configure them to communicate across the network with each other.

• Lab Project 10.2 Demonstrate network connectivity using Windows command-line tools.

chapter 11 Authentication and Remote Access

We should set a national goal of making computers and Internet access available for every American.

O

—WILLIAM JEFFERSON CLINTON

In this chapter, you will learn how to

Identify the differences among user, group, and role management

Implement password and domain password policies

Describe methods of account management (SSO, time of day, logical token, account expiration)

Describe methods of access management (MAC, DAC, and RBAC)

Discuss the methods and protocols for remote access to networks

Identify authentication, authorization, and accounting (AAA) protocols

Explain authentication methods and the security implications in their use

Implement virtual private networks (VPNs) and their security aspects

Describe Internet Protocol Security (IPsec) and its use in securing communications

n single-user systems such as PCs, the individual user typically has access to most of the system’s resources, processing capability, and stored data. On multiuser systems, such as servers and mainframes, an

individual user typically has very limited access to the system and the data stored on that system. An administrator responsible for managing and maintaining the multiuser system has much greater access. So how does the computer system know which users should have access to what data? How does the operating system know what applications a user is allowed to use? On early computer systems, anyone with physical access had fairly

significant rights to the system and could typically access any file or execute any application. As computers became more popular and it became obvious that some way of separating and restricting users was needed, the concepts of users, groups, and privileges came into being (privileges mean you have the ability to “do something” on a computer system such as create a directory, delete a file, or run a program). These concepts continue to be developed and refined and are now part of what

we call privilege management. Privilege management is the process of restricting a user’s ability to

interact with the computer system. Essentially, everything a user can do to or with a computer system falls into the realm of privilege management. Privilege management occurs at many different points within an operating system or even within applications running on a particular operating system. Remote access is another key issue for multiuser systems in today’s

world of connected computers. Isolated computers, not connected to networks or the Internet, are rare items these days. Except for some special-purpose machines, most computers need interconnectivity to fulfill their purpose. Remote access enables users outside a network to have network access and privileges as if they were inside the network. Being outside a network means that the user is working on a machine that is not physically connected to the network and must therefore establish a connection through a remote means, such as by dialing in, connecting via the Internet, or connecting through a wireless connection. Authentication is the process of establishing a user’s identity to enable

the granting of permissions. To establish network connections, a variety of methods are used, the choice of which depends on network type, the hardware and software employed, and any security requirements.

User, Group, and Role Management To manage the privileges of many different people effectively on the same system, a mechanism for separating people into distinct entities (users) is required, so you can control access on an individual level. At the same time, it’s convenient and efficient to be able to lump users together when granting many different people (groups) access to a resource at the same time. At other times, it’s useful to be able to grant or restrict access based on a person’s job or function within the organization (role). While you can manage privileges on the basis of users alone, managing user, group, and role assignments together is far more convenient and efficient.

Tech Tip

User ID vs. Username The terms “user ID” and “username” are sometimes used interchangeably, but traditionally the term user ID is more often associated with UNIX operating systems. In UNIX operating systems, each user is identified by an unsigned integer called a user identifier, often shortened to user ID.

User The term user generally applies to any person accessing a computer system. In privilege management, a user is a single individual, such as “John Forthright” or “Sally Jenkins.” This is generally the lowest level addressed by privilege management and the most common area for addressing access, rights, and capabilities. When accessing a computer system, each user is generally given a username—a unique alphanumeric identifier he or she will use to identify himself or herself when logging into or accessing the system. When developing a scheme for selecting usernames, you should keep in mind that usernames must be unique to each user, but they must also be fairly easy for the user to remember and use.

Exam Tip: A username is a unique alphanumeric identifier used to identify a user to a computer system. Permissions control what a user is allowed to do with objects on a computer system— what files they can open, what printers they can use, and so on. In Windows security models, permissions define the actions a user can perform on an object (open a file, delete a folder, and so on). Rights define the actions a user can perform on the system itself, such as change the time, adjust auditing levels, and so on. Rights are typically applied to operating system–level tasks.

With some notable exceptions, in general a user who wants to access a computer system must first have a username created for him on the system

he wishes to use. This is usually done by a system administrator, security administrator, or other privileged user, and this is the first step in privilege management—a user should not be allowed to create their own account. Once the account is created and a username is selected, the

administrator can assign specific permissions to that user. Permissions control what the user is allowed to do with objects on the system—which files he may access, which programs he may execute, and so on. While PCs typically have only one or two user accounts, larger systems such as servers and mainframes can have hundreds of accounts on the same system. Figure 11.1 shows the Users management tab of the Computer Management utility on a Windows Server 2008 system. Note that several user accounts have been created on this system, each identified by a unique username.

• Figure 11.1 Users tab on a Windows Server 2008 system

A few “special” user accounts don’t typically match up one-to-one with a real person. These accounts are reserved for special functions and typically have much more access and control over the computer system than the average user account. Two such accounts are the administrator account under Windows and the root account under UNIX. Each of these accounts is also known as the superuser—if something can be done on the system, the superuser has the power to do it. These accounts are not typically assigned to a specific individual and are restricted, accessed only when the full capabilities of that account are required.

Auditing user accounts, group membership, and password strength on a regular basis is an extremely important security control. Many compliance audits focus on the presence or lack of industry-accepted security controls.

Due to the power possessed by these accounts, and the few, if any, restrictions placed on them, they must be protected with strong passwords that are not easily guessed or obtained. These accounts are also the most common targets of attackers—if the attacker can gain root access or assume the privilege level associated with the root account, she can bypass most access controls and accomplish anything she wants on that system.

Tech Tip

Generic Accounts Generic accounts are accounts without a named user behind them. These can be employed for special purposes, such as running services and batch processes, but because they cannot be attributed to an individual, they should not have login ability. It is also important that if they have elevated privileges, their activities be continually monitored as to what functions they are performing versus what they are expected to be doing. General use of generic accounts should be avoided because of the increased risk associated with no attribution capability.

Another account that falls into the “special” category is the system account used by Windows operating systems. The system account has the same file privileges as the administrator account and is used by the operating system and by services that run under Windows. By default, the system account is granted full control to all files on an NTFS volume. Services and processes that need the capability to log on internally within Windows will use the system account—for example, the DNS Server and DHCP Server services in Windows Server 2008 use the Local System account.

Group Under privilege management, a group is a collection of users with some common criteria, such as a need for access to a particular dataset or group of applications. A group can consist of one user or hundreds of users, and each user can belong to one or more groups. Figure 11.2 shows a common approach to grouping users—building groups based on job function.

• Figure 11.2 Logical representation of groups

By assigning membership in a specific group to a user, you make it much easier to control that user’s access and privileges. For example, if

every member of the engineering department needs access to product development documents, administrators can place all the users in the engineering department in a single group and allow that group to access the necessary documents. Once a group is assigned permissions to access a particular resource, adding a new user to that group will automatically allow that user to access that resource. In effect, the user “inherits” the permissions of the group as soon as she is placed in that group. As Figure 11.3 shows, a computer system can have many different groups, each with its own rights and permissions.

• Figure 11.3 Groups tab on a Windows Server 2008 system

As you can see from the description for the Administrators group in Figure 11.3, this group has complete and unrestricted access to the system.

This includes access to all files, applications, and datasets. Anyone who belongs to the Administrators group or is placed in this group will have a great deal of access and control over the system. Some operating systems, such as Windows, have built-in groups—

groups that are already defined within the operating system, such as Administrators, Power Users, and Everyone. The whole concept of groups revolves around making the tasks of assigning and managing permissions easier, and built-in groups certainly help to make these tasks easier. Individual users accounts can be added to built-in groups, allowing administrators to grant permission sets to users quickly and easily without having to specify permissions manually. For example, adding a user account named “bjones” to the Power Users group gives bjones all the permissions assigned to the built-in Power Users group, such as installing drivers, modifying settings, and installing software.

Role Another common method of managing access and privileges is by roles. A role is usually synonymous with a job or set of functions. For example, the role of security admin in Microsoft SQL Server may be applied to someone who is responsible for creating and managing logins, reading error logs, and auditing the application. Security admins need to accomplish specific functions and need access to certain resources that other users do not—for example, they need to be able to create and delete logins, open and read error logs, and so on. In general, anyone serving in the role of security admin needs the same rights and privileges as every other security admin. For simplicity and efficiency, rights and privileges can be assigned to the role security admin, and anyone assigned to fulfill that role automatically has the correct rights and privileges to perform the required tasks.

Password Policies

The username/password combination is by far the most common means of controlling access to applications, web sites, and computer systems. The average user may have a dozen or more username and password combinations between school, work, and personal use. To help users select a good, difficult-to-guess password, most organizations implement and enforce a password policy, which typically has the following components:

Tech Tip

TOTP A Time-based One-Time Password (TOTP) generator uses the current time as one of the seeds in a one-time password. This prevents replay attacks utilizing a captured password.

Password construction How many characters a password should have; the use of capitalization, numbers, and special characters; not basing the password on a dictionary word or personal information; not making the password a slight modification of an existing password; and so on

Reuse restrictions Whether or not passwords can be reused, and, if so, with what frequency (how many different passwords must you use before you can use one you’ve used before)

Duration The minimum and maximum number of days a password can be used before it can be changed or must be changed

Protection of passwords Not writing down passwords where others can find them, not saving passwords and not allowing automated logins, not sharing passwords with other users, and so on

Consequences Consequences associated with violation of or noncompliance with the policy

The SANS Institute offers several examples of password policies (along with many other common information security policies) on its web site

(www.sans.org—type password policy into the search box at the top of the SANS web site). The overall guidance established by the organization’s security policy should be refined into specific guidance that administrators can enforce at the operating system level.

Exam Tip: A password policy is a set of rules designed to enhance computer security by requiring users to employ and maintain strong passwords. A domain password policy is a password policy that applies to a specific domain.

Domain Password Policy A domain password policy is a password policy for a specific domain. As these policies are usually associated with the Windows operating system, a domain password policy is implemented and enforced on the domain controller, which is a computer that responds to security authentication requests, such as logging into a computer, for a Windows domain. The domain password policy usually falls under a group policy object (GPO) and has the following elements (see Figure 11.4):

• Figure 11.4 Password policy options in Windows Local Security Policy

Enforce password history Tells the system how many passwords to remember and does not allow a user to reuse an old password.

Maximum password age Specifies the maximum number of days a password may be used before it must be changed.

Minimum password age Specifies the minimum number of days a password must be used before it can be changed again.

Minimum password length Specifies the minimum number of

characters that must be used in a password.

Password must meet complexity requirements Specifies that the password must meet the minimum length requirement and have characters from at least three of the following four groups: English uppercase characters (A through Z), English lowercase characters (a through z), numerals (0 through 9), and non-alphabetic characters (such as !, $, #, %).

Store passwords using reversible encryption Reversible encryption is a form of encryption that can easily be decrypted and is essentially the same as storing a plaintext version of the password (because it’s so easy to reverse the encryption and get the password). This should be used only when applications use protocols that require the user’s password for authentication (such as Challenge-Handshake Authentication Protocol, or CHAP).

Not only is it essential to ensure every account has a strong password, but also it is essential to disable or delete unnecessary accounts. If your system does not need to support guest or anonymous accounts, then disable them. When user or administrator accounts are no longer needed, remove or disable them. As a best practice, all user accounts should be audited periodically to ensure there are no unnecessary, outdated, or unneeded accounts on your systems.

Domains are logical groups of computers that share a central directory database, known as the Active Directory database for the more recent Windows operating systems. The database contains information about the user accounts and security information for all resources identified within the domain. Each user within the domain is assigned his or her own unique account (that is, a domain is not a single account shared by multiple users), which is then assigned access to specific resources within the domain. In operating systems that provide domain capabilities, the password policy is set in the root container for the domain and applies to all users within that domain. Setting a password policy for a domain is similar to setting other

password policies in that the same critical elements need to be considered (password length, complexity, life, and so on). If a change to one of these elements is desired for a group of users, a new domain needs to be created because the domain is considered a security boundary. In a Windows operating system that employs Active Directory, the domain password policy can be set in the Active Directory Users and Computers menu in the Administrative Tools section of the Control Panel.

Tech Tip

Calculating Unique Password Combinations One of the primary reasons administrators require users to have longer passwords that use upper- and lowercase letters, numbers, and at least one “special” character is to help deter password-guessing attacks. One popular password-guessing technique, called a brute-force attack, uses software to guess every possible password until one matches a user’s password. Essentially, a brute force-attack tries a, then aa, then aaa, and so on until it runs out of combinations or gets a password match. Increasing both the pool of possible characters that can be used in the password and the number of characters required in the password can exponentially increase the number of “guesses” a brute-force program needs to perform before it runs out of possibilities. For example, if our password policy requires a three- character password that uses only lowercase letters, there are only 17,576 possible passwords (26 possible characters, 3 characters long is 263 combinations). Requiring a six-character password increases that number to 308,915,776 possible passwords (266). An eight-character password with upper- and lowercase, special symbol, and a number increases the possible passwords to 708 or over 576 trillion combinations Precomputed hashes in rainbow tables can also be used to brute force past shorter

passwords. As the length increases, so does the size of the rainbow table.

Single Sign-On To use a system, users must be able to access it, which they usually do by supplying their user IDs (or usernames) and corresponding passwords. As any security administrator knows, the more systems a particular user has access to, the more passwords that user must have and remember. The

natural tendency for users is to select passwords that are easy to remember, or even the same password for use on the multiple systems they access. Wouldn’t it be easier for the user simply to log in once and have to remember only a single, good password? This is made possible with a technology called single sign-on. Single sign-on (SSO) is a form of authentication that involves the

transferring of credentials between systems. As more and more systems are combined in daily use, users are forced to have multiple sets of credentials. A user may have to log into three, four, five, or even more systems every day just to do her job. Single sign-on allows a user to transfer her credentials, so that logging into one system acts to log her into all of them. Once the user has entered a user ID and password, the single sign-on system passes these credentials transparently to other systems so that repeated logons are not required. Put simply, you supply the right username and password once and you have access to all the applications and data you need, without having to log in multiple times and remember many different passwords. From a user standpoint, SSO means you need to remember only one username and one password. From an administration standpoint, SSO can be easier to manage and maintain. From a security standpoint, SSO can be even more secure, as users who need to remember only one password are less likely to choose something too simple or something so complex they need to write it down. Figure 11.5 shows a logical depiction of the SSO process:

• Figure 11.5 Single sign-on process

1. The user signs in once, providing a username and password to the SSO server.

2. The SSO server provides authentication information to any resource the user accesses during that session. The server interfaces with the other applications and systems—the user does not need to log into each system individually.

Exam Tip: The CompTIA Security+ exam will very likely contain questions regarding single sign-on because it is such a prevalent topic and a very common approach to multisystem authentication.

In reality, SSO is usually a little more difficult to implement than vendors would lead you to believe. To be effective and useful, all your applications need to be able to access and use the authentication provided by the SSO process. The more diverse your network, the less likely this is to be the case. If your network, like most, contains different operating systems, custom applications, and a diverse user base, SSO may not even be a viable option.

Time of Day Restrictions Some organizations need to tightly control certain users, groups, or even roles and limit access to certain resources to specific days and times. Most server-class operating systems enable administrators to implement time of day restrictions that limit when a user can log in, when certain resources can be accessed, and so on. Time of day restrictions are usually specified for individual accounts, as shown in Figure 11.6.

• Figure 11.6 Logon hours for Guest account

From a security perspective, time of day restrictions can be very useful. If a user normally accesses certain resources during normal business hours, an attempt to access these resources outside this time period (either at night or on the weekend) might indicate an attacker has gained access to or is trying to gain access to that account. Specifying time of day restrictions can also serve as a mechanism to enforce internal controls of critical or sensitive resources. Obviously, a drawback to enforcing time of day restrictions is that it means that a user can’t go to work outside of normal

hours to “catch up” with work tasks. As with all security policies, usability and security must be balanced in this policy decision.

Be careful implementing time of day restrictions. Some operating systems give you the option of disconnecting users as soon as their “allowed login time” expires regardless of what the user is doing at the time. The more commonly used approach is to allow currently logged-in users to stay connected but reject any login attempts that occur outside of allowed hours.

Tokens While the username/password combination has been and continues to be the cheapest and most popular method of controlling access to resources, many organizations look for a more secure and tamper-resistant form of authentication. Usernames and passwords are “something you know” (which can be used by anyone else who knows or discovers the information). A more secure method of authentication is to combine the “something you know” with “something you have.” A token is an authentication factor that typically takes the form of a physical or logical entity that the user must be in possession of to access their account or certain resources. Most tokens are physical tokens that display a series of numbers that

changes every 30 to 90 seconds, such as the token pictured in Figure 11.7 from Blizzard Entertainment. This sequence of numbers must be entered when the user is attempting to log in or access certain resources. The ever- changing sequence of numbers is synchronized to a remote server such that when the user enters the correct username, password, and matching sequence of numbers, he is allowed to log in. Even if an attacker obtains the username and password, the attacker cannot log in without the matching sequence of numbers. Other physical tokens include Common Access Cards (CACs), USB tokens, smart cards, and PC cards.

• Figure 11.7 Token authenticator from Blizzard Entertainment

Tokens may also be implemented in software. Software tokens still provide two-factor authentication but don’t require the user to have a physical device on hand. Some tokens require software clients that store a symmetric key (sometimes called a seed record) in a secured location on the user’s device (laptop, desktop, tablet, and so on). Other software tokens use public key cryptography. Asymmetric cryptography solutions, such as public key cryptography, often associate a PIN with a specific user’s token. To log in or access critical resources, the user must supply the correct PIN. The PIN is stored on a remote server and is used during the authentication process so that if a user presents the right token, but not the right PIN, the user’s access can be denied. This helps prevent an attacker from gaining access if he gets a copy of or gains access to the software token.

Cross Check Symmetric and Asymmetric Cryptography You learned about symmetric and asymmetric cryptography in Chapter 5. What is the difference

between the two methods? Which one uses public keys?

Tech Tip

Best Practice: Password Expiration One of the best practices an organization can implement is to attach an expiration date to user passwords. This helps ensure that if a password is compromised, the period that the account remains compromised is limited. In most environments and operating systems, this is expressed in terms of the number of days before the password expires and is no longer valid. For example, a maximum password age of 90 days means that a particular password will expire 90 days after that password was initially set to its current value.

Account and Password Expiration Another common restriction that can be enforced in many access control mechanisms is either (or both) an account expiration or password expiration feature. This allows administrators to specify a period of time for which a password or an account will be active. For password expiration, when the expiration date is reached, the user generally is asked to create a new password. This means that if the password (and thus the account) has been compromised when the expiration date is reached and a new password is set, the attacker will again (hopefully) be locked out of the system. The attacker can’t change the password himself, since the user would then be locked out and would contact an administrator to have the password reset, thus again locking out the attacker. Another attack option would involve the attacker setting a new

password on the compromised account and then attempting to reset the account back to the original, compromised password. If the attacker is successful, a new expiration time would be set for the account but the old password would still be used and the user would not be locked out of their account; in most cases, the user wouldn’t notice anything had happened at all as their old password would continue to work. This is one reason why a

password history mechanism should be used. The history is used to keep track of previously used passwords so that they cannot be reused.

Tech Tip

Heartbleed In 2014 a vulnerability that could cause user credentials to be exposed was discovered in millions of systems. Called the Heartbleed incident, this resulted in numerous users being told to change their passwords because of potential compromise. Users were also warned of the dangers of reusing passwords across different accounts. Although this makes passwords easier to remember, it also improves guessing chances. What made this whole effort of protecting your passwords particularly challenging is that the breach was widespread— virtually all Linux systems—and the patching rate was uneven, so people could be suffering multiple exposures over time. After one year, an estimated 40% of all compromised systems remained unpatched. This highlights the importance of not reusing passwords across multiple accounts.

Security Controls and Permissions If multiple users share a computer system, the system administrator likely needs to control who is allowed to do what when it comes to viewing, using, or changing system resources. While operating systems vary in how they implement these types of controls, most operating systems use the concepts of permissions and rights to control and safeguard access to resources. As we discussed earlier, permissions control what a user is allowed to do with objects on a system and rights define the actions a user can perform on the system itself. Let’s examine how the Windows operating systems implement this concept. The Windows operating systems use the concepts of permissions and

rights to control access to files, folders, and information resources. When using the NTFS file system, administrators can grant users and groups permission to perform certain tasks as they relate to files, folders, and Registry keys. The basic categories of NTFS permissions are as follows:

Exam Tip: Permissions can be applied to specific users or groups to control that user’s or group’s ability to view, modify, access, use, or delete resources such as folders and files.

Full Control A user/group can change permissions on the folder/file, take ownership if someone else owns the folder/file, delete subfolders and files, and perform actions permitted by all other NTFS folder permissions.

Modify Users/groups can view and modify files/ folders and their properties, can delete and add files/folders, and can delete or add properties to a file/folder.

Read & Execute Users/groups can view the file/folder and can execute scripts and executables but cannot make any changes (files/folders are read-only).

List Folder Contents A user/group can list only what is inside the folder (applies to folders only).

Read Users/groups can view the contents of the file/folder and the file/folder properties.

Write Users/groups can write to the file or folder.

Figure 11.8 shows the permissions on a folder called Data from a Windows Server system. In the top half of the Permissions window are the users and groups that have permissions for this folder. In the bottom half of the window are the permissions assigned to the highlighted user or group.

• Figure 11.8 Permissions for the Data folder

The Windows operating system also uses user rights or privileges to determine what actions a user or group is allowed to perform or access. These user rights are typically assigned to groups, as it is easier to deal with a few groups than to assign rights to individual users, and they are usually defined in either a group or a local security policy. The list of user rights is quite extensive but a few examples of user rights are

Log on locally Users/groups can attempt to log onto the local system itself.

Access this computer from the network Users/groups can attempt to access this system through the network connection.

Manage auditing and security log Users/groups can view, modify, and delete auditing and security log information.

Rights tend to be actions that deal with accessing the system itself, process control, logging, and so on. Figure 11.9 shows the user rights contained in the local security policy on a Windows system.

• Figure 11.9 User Rights Assignment options from Windows Local Security Policy

Folders and files are not the only things that can be safeguarded or controlled using permissions. Even access and use of peripherals, such as printers, can be controlled using permissions. Figure 11.10 shows the Security tab from a printer attached to a Windows system. Permissions can be assigned to control who can print to the printer, who can manage documents and print jobs sent to the printer, and who can manage the printer itself. With this type of granular control, administrators have a great deal of control over how system resources are used and who uses them.

• Figure 11.10 Security tab showing printer permissions in Windows

Exam Tip: Although it is very important to get security settings “right the first time,” it is just as important to perform routine audits of security settings such as user accounts, group memberships, file permissions, and so on.

A very important concept to consider when assigning rights and privileges to users is the concept of least privilege. Least privilege requires that users be given the absolute minimum number of rights and privileges required to perform their authorized duties. For example, if a user does not need the ability to install software on their own desktop to perform their job, then don’t give them that ability. This reduces the likelihood the user will load malware, insecure software, or unauthorized applications onto their system.

Access Control Lists The term access control list (ACL) is used in more than one manner in the field of computer security. When discussing routers and firewalls, an ACL is a set of rules used to control traffic flow into or out of an interface or network. When discussing system resources, such as files and folders, an ACL lists permissions attached to an object—who is allowed to view, modify, move, or delete that object. To illustrate this concept, consider an example. Figure 11.11 shows the

access control list (permissions) for the Data folder. The user identified as Billy Williams has Read & Execute, List Folder Contents, and Read permissions, meaning this user can open the folder, see what’s in the folder, and so on. Figure 11.12 shows the permissions for a user identified as Leah Jones, who has only Read permissions on the same folder.

• Figure 11.11 Permissions for Billy Williams on the Data folder

• Figure 11.12 Permissions for Leah Jones on the Data folder

In computer systems and networks, there are several ways that access controls can be implemented. An access control matrix provides the simplest framework for illustrating the process. An example of an access control matrix is provided in Table 11.1. In this matrix, the system is keeping track of two processes, two files, and one hardware device. Process 1 can read both File 1 and File 2 but can write only to File 1. Process 1 cannot access Process 2, but Process 2 can execute Process 1. Both processes have the ability to write to the printer.

Table 11.1 An Access Control Matrix

While simple to understand, the access control matrix is seldom used in computer systems because it is extremely costly in terms of storage space and processing. Imagine the size of an access control matrix for a large network with hundreds of users and thousands of files.

Mandatory Access Control (MAC) Mandatory access control (MAC) is the process of controlling access to information based on the sensitivity of that information and whether or not the user is operating at the appropriate sensitivity level and has the authority to access that information. Under a MAC system, each piece of information and every system resource (files, devices, networks, and so on) is labeled with its sensitivity level (such as Public, Engineering

Private, Jones Secret). Users are assigned a clearance level that sets the upper boundary of the information and devices that they are allowed to access.

Exam Tip: Mandatory access control restricts access based on the sensitivity of the information and whether or not the user has the authority to access that information.

The access control and sensitivity labels are required in a MAC system. Labels are defined and then assigned to users and resources. Users must then operate within their assigned sensitivity and clearance levels—they don’t have the option to modify their own sensitivity levels or the levels of the information resources they create. Due to the complexity involved, MAC is typically run only on systems where security is a top priority such as Trusted Solaris, OpenBSD, and SELinux.

Tech Tip

MAC Objective Mandatory access controls are often mentioned in discussions of multilevel security. For multilevel security to be implemented, a mechanism must be present to identify the classification of all users and files. A file identified as Top Secret (has a label indicating that it is Top Secret) may be viewed only by individuals with a Top Secret clearance. For this control mechanism to work reliably, all files must be marked with appropriate controls and all user access must be checked. This is the primary goal of MAC.

Figure 11.13 illustrates MAC in operation. The information resource on the left has been labeled “Engineering Secret,” meaning only users in the Engineering group operating at the Secret sensitivity level or above can access that resource. The top user is operating at the Secret level but is not a member of Engineering and is denied access to the resource. The middle user is a member of Engineering but is operating at a Public sensitivity

level and is therefore denied access to the resource. The bottom user is a member of Engineering, is operating at a Secret sensitivity level, and is allowed to access the information resource.

• Figure 11.13 Logical representation of mandatory access control

Discretionary Access Control (DAC) Discretionary access control (DAC) is the process of using file permissions and optional ACLs to restrict access to information based on a user’s identity or group membership. DAC is the most common access control system and is commonly used in both UNIX and Windows operating systems. The “discretionary” part of DAC means that a file or

resource owner has the ability to change the permissions on that file or resource.

Tech Tip

Multilevel Security In the U.S. government, the following security labels are used to classify information and information resources for MAC systems:

Top Secret The highest security level and is defined as information that would cause “exceptionally grave damage” to national security if disclosed.

Secret The second highest level and is defined as information that would cause “serious damage” to national security if disclosed.

Confidential The lowest level of classified information and is defined as information that would “damage” national security if disclosed.

For Official Use Only Information that is unclassified but not releasable to public or unauthorized parties. Sometimes called Sensitive But Unclassified (SBU)

Unclassified Not an official classification level.

The labels work in a top-down fashion so that an individual holding a Secret clearance would have access to information at the Secret, Confidential, and Unclassified levels. An individual with a Secret clearance would not have access to Top Secret resources, as that label is above the highest level of the individual’s clearance.

Under UNIX operating systems, file permissions consist of three distinct parts:

Owner permissions (read, write, and execute) The owner of the file

Group permissions (read, write, and execute) The group to which the owner of the file belongs

World permissions (read, write, and execute) Anyone else who is not the owner and does not belong to the group to which the owner of the file belongs

Exam Tip: Discretionary access control restricts access based on the user’s identity or group membership.

For example, suppose a file called secretdata has been created by the owner of the file, Luke, who is part of the Engineering group. The owner permissions on the file would reflect Luke’s access to the file (as the owner). The group permissions would reflect the access granted to anyone who is part of the Engineering group. The world permissions would represent the access granted to anyone who is not Luke and is not part of the Engineering group. In UNIX, a file’s permissions are usually displayed as a series of nine

characters, with the first three characters representing the owner’s permissions, the second three characters representing the group permissions, and the last three characters representing the permissions for everyone else, or for the world. This concept is illustrated in Figure 11.14.

• Figure 11.14 Discretionary file permissions in the UNIX environment

Suppose the file secretdata is owned by Luke with group permissions

for Engineering (because Luke is part of the Engineering group), and the permissions on that file are rwx, rw-, and ---, as shown in Figure 11.14. This would mean that:

Luke can read, write, and execute the file (rwx).

Members of the Engineering group can read and write the file but not execute it (rw-).

The world has no access to the file and can’t read, write, or execute it (---).

Remember that under the DAC model, the file’s owner, Luke, can change the file’s permissions any time he wants.

Role-Based Access Control (RBAC) Access control lists can be cumbersome and can take time to administer properly. Role-based access control (RBAC) is the process of managing access and privileges based on the user’s assigned roles. RBAC is the access control model that most closely resembles an organization’s structure. In this scheme, instead of each user being assigned specific access permissions for the objects associated with the computer system or network, that user is assigned a set of roles that the user may perform. The roles are in turn assigned the access permissions necessary to perform the tasks associated with the role. Users will thus be granted permissions to objects in terms of the specific duties they must perform—not just because of a security classification associated with individual objects.

As defined by the “Orange Book,” a Department of Defense document (in the “rainbow series”) that at one time was the standard for describing what constituted a trusted computing system, a discretionary access control (DAC) is “a means of restricting access to objects based on the identity of subjects and/or groups to which they belong. The controls are discretionary in the sense that a subject with a certain access permission is capable of passing that permission

(perhaps indirectly) on to any other subject (unless restrained by mandatory access control).”

Under RBAC, you must first determine the activities that must be performed and the resources that must be accessed by specific roles. For example, the role of “securityadmin” in Microsoft SQL Server must be able to create and manage logins, read error logs, and audit the application. Once all the roles are created and the rights and privileges associated with those roles are determined, users can then be assigned one or more roles based on their job functions. When a role is assigned to a specific user, the user gets all the rights and privileges assigned to that role.

Exam Tip: Role-based and rule-based access control can both be abbreviated as RBAC. Standard convention is for RBAC to be used to denote role-based access control. A seldom-seen acronym for rule-based access control is RB-RBAC. Role-based focuses on the user’s role (administrator, backup operator, and so on). Rule-based focuses on predefined criteria such as time of day (users can only log in between 8 A.M. and 6 P.M.) or type of network traffic (web traffic is allowed to leave the organization).

Unfortunately, in reality, administrators often find themselves in a position of working in an organization where more than one user has multiple roles or even access to multiple accounts (a situation quite common in smaller organizations). Users with multiple accounts tend to select the same or similar passwords for those accounts, thereby increasing the chance one compromised account can lead to the compromise of other accounts accessed by that user. Where possible, administrators should first eliminate shared or additional accounts for users and then examine the possibility of combining roles or privileges to reduce the “account footprint” of individual users.

Rule-Based Access Control Rule-based access control is yet another method of managing access and

privileges (and unfortunately shares the same acronym as role-based access control). In this method, access is either allowed or denied based on a set of predefined rules. Each object has an associated ACL (much like DAC), and when a particular user or group attempts to access the object, the appropriate rule is applied.

Exam Tip: The CompTIA Security+ exam will very likely expect you to be able to differentiate between the four major forms of access control discussed here: mandatory access control, discretionary access control, role-based access control, and rule-based access control.

A good example for rule-based access control is permitted logon hours. Many operating systems give administrators the ability to control the hours during which users can log in. For example, a bank may allow its employees to log in only between the hours of 8 A.M. and 6 P.M. Monday through Saturday. If a user attempts to log in outside of these hours, 3 A.M. on Sunday for example, then the rule will reject the login attempt whether or not the user supplies valid login credentials.

Attribute-Based Access Control (ABAC) Attribute-based access control (ABAC) is a new access control schema based on the use of attributes associated with an identity. These can use any type of attributes (user attributes, resource attributes, environment attributes, and so on), such as location, time, activity being requested, and user credentials. An example would be a doctor getting one set of access for a specific patient versus a different patient. ABAC can be represented via the eXtensible Access Control Markup Language (XACML), a standard that implements attribute- and policy-based access control schemes.

Account Expiration

In addition to all the other methods of controlling and restricting access, most modern operating systems allow administrators to specify the length of time an account is valid and when it “expires” or is disabled. This is a great method for controlling temporary accounts, or accounts for contractors or contract employees. For these accounts, the administrator can specify an expiration date; when the date is reached, the account automatically becomes locked out and cannot be logged into without administrator intervention. A related action can be taken with accounts that never expire: they can automatically be marked “inactive” and locked out if they have been unused for a specified number of days. Account expiration is similar to password expiration, in that it limits the time window of potential compromise. When an account has expired, it cannot be used unless the expiration deadline is extended.

Tech Tip

Disabling Accounts When an administrator needs to end a user’s access, for instance upon termination, there are several options. The best option is to disable the account but leave it in the system. This preserves account permission chains and prevents reuse of a user ID, leading to potential confusion later when examining logs.

Similarly, organizations must define whether accounts are deleted or disabled when no longer needed. Deleting an account removes the account from the system permanently, whereas disabling an account leaves it in place but marks it as unusable. Many organizations disable accounts for a period of time after an employee departs (30 or more days) prior to deleting the account. This prevents anyone from using the account and allows administrators to reassign files, forward mail, and “clean up” before taking any permanent actions on the account.

Preventing Data Loss or Theft

Identity theft and commercial espionage have become very large and lucrative criminal enterprises over the past decade. Hackers are no longer merely content to compromise systems and deface web sites. In many attacks performed today, hackers are after intellectual property, business plans, competitive intelligence, personal information, credit card numbers, client records, or any other information that can be sold, traded, or manipulated for profit. This has created a whole industry of technical solutions labeled data loss prevention (DLP) solutions. It can be assumed that a hacker has assumed the identity of an

authorized user, and DLP solutions exist to prevent the exfiltration of data regardless of access control restrictions. DLP solutions come in many forms, and each of these solutions has strengths and weaknesses. The best solution is a combination of security elements, some to secure data in storage (encryption) and some in the form of monitoring (proxy devices to monitor data egress for sensitive data), and even NetFlow analytics to identify new bulk data transfer routes.

The Remote Access Process The process of connecting by remote access involves two elements: a temporary network connection and a series of protocols to negotiate privileges and commands. The temporary network connection can occur via a dial-up service, the Internet, wireless access, or any other method of connecting to a network. Once the connection is made, the primary issue is authenticating the identity of the user and establishing proper privileges for that user. This is accomplished using a combination of protocols and the operating system on the host machine. The three steps in the establishment of proper privileges are

authentication, authorization, and accounting, commonly referred to simply as AAA. Authentication is the matching of user-supplied credentials to previously stored credentials on a host machine, and it usually involves an account username and password. Once the user is authenticated, the authorization step takes place. Authorization is the

granting of specific permissions based on the privileges held by the account. Does the user have permission to use the network at this time, or is her use restricted? Does the user have access to specific applications, such as mail and FTP, or are some of these restricted? These checks are carried out as part of authorization, and in many cases this is a function of the operating system in conjunction with its established security policies. Accounting is the collection of billing and other detail records. Network access is often a billable function, and a log of how much time, bandwidth, file transfer space, or other resources were used needs to be maintained. Other accounting functions include keeping detailed security logs to maintain an audit trail of tasks being performed.

Tech Tip

Securing Remote Connections By using encryption, remote access protocols can securely authenticate and authorize a user according to previously established privilege levels. The authorization phase can keep unauthorized users out, but after that, encryption of the communications channel becomes very important in preventing nonauthorized users from breaking in on an authorized session and hijacking an authorized user’s credentials. As more and more networks rely on the Internet for connecting remote users, the need for and importance of secure remote access protocols and secure communication channels will continue to grow.

When a user connects to the Internet through an ISP, this is similarly a case of remote access—the user is establishing a connection to her ISP’s network, and the same security issues apply. The issue of authentication, the matching of user-supplied credentials to previously stored credentials on a host machine, is usually done via a user account name and password. Once the user is authenticated, the authorization step takes place. Remote authentication usually takes the common form of an end user submitting his credentials via an established protocol to a remote access server (RAS), which acts upon those credentials, either granting or denying access.

Access controls define what actions a user can perform or what objects a user is allowed to access. Access controls are built upon the foundation of elements designed to facilitate the matching of a user to a process. These elements are identification, authentication, and authorization. There are a myriad of details and choices associated with setting up remote access to a network, and to provide for the management of these options, it is important for an organization to have a series of remote access policies and procedures spelling out the details of what is permitted and what is not for a given network.

Identification Identification is the process of ascribing a computer ID to a specific user, computer, network device, or computer process. The identification process is typically performed only once, when a user ID is issued to a particular user. User identification enables authentication and authorization to form the basis for accountability. For accountability purposes, user IDs should not be shared, and for security purposes, they should not be descriptive of job function. This practice enables you to trace activities to individual users or computer processes so that they can be held responsible for their actions. Identification links the logon ID or user ID to credentials that have been submitted previously to either HR or the IT staff. A required characteristic of user IDs is that they must be unique so that they map back to the credentials presented when the account was established.

Tech Tip

Federation Federated identity management is an agreement between multiple enterprises that lets parties use the same identification data to obtain access to the networks of all enterprises in the group. This federation enables access to be managed across multiple systems in common trust levels.

Authentication Authentication is the process of binding a specific ID to a specific computer connection. Two items need to be presented to cause this binding to occur—the user ID, and some “secret” to prove that the user is the valid possessor of the credentials. Historically, three categories of secrets are used to authenticate the identity of a user: what users know, what users have, and what users are. Today an additional category is used: what users do. These methods can be used individually or in combination. These

controls assume that the identification process has been completed and the identity of the user has been verified. It is the job of authentication mechanisms to ensure that only valid users are admitted. Described another way, authentication is using some mechanism to prove that you are who you claimed to be when the identification process was completed. The most common method of authentication is the use of a password.

For greater security, you can add an element from a separate group, such as a smart card token—something a user has in her possession. Passwords are common because they are one of the simplest forms and use user memory as a prime component. Because of their simplicity, passwords have become ubiquitous across a wide range of authentication systems. Another method to provide authentication involves the use of something

that only valid users should have in their possession. A physical-world example of this would be a simple lock and key. Only those individuals with the correct key will be able to open the lock and thus gain admittance to a house, car, office, or whatever the lock was protecting. A similar method can be used to authenticate users for a computer system or network (though the key may be electronic and could reside on a smart card or similar device). The problem with this technology, however, is that people do lose their keys (or cards), which means not only that the user can’t log into the system but that somebody else who finds the key may then be able to access the system, even though they are not authorized. To address this problem, a combination of the something-you-know and something-you-

have methods is often used so that the individual with the key is also required to provide a password or passcode. The key is useless unless the user knows this code.

Tech Tip

Categories of Shared Secrets for Authentication Originally published by the U.S. government in one of the “rainbow series” of manuals on computer security, the categories of shared “secrets” are

What users know (such as a password) What users have (such as tokens)

What users are (static biometrics such as fingerprints or iris pattern) Today, because of technological advances, a new category has emerged, patterned after subconscious behavior:

What users do (dynamic biometrics such as typing patterns or gait)

The third general method to provide authentication involves something that is unique about you. We are accustomed to this concept in our physical world, where our fingerprints or a sample of our DNA can be used to identify us. This same concept can be used to provide authentication in the computer world. The field of authentication that uses something about you or something that you are is known as biometrics. A number of different mechanisms can be used to accomplish this type of authentication, such as a fingerprint, iris, retinal, or hand geometry scan. All of these methods obviously require some additional hardware in order to operate. The inclusion of fingerprint readers on laptop computers is becoming common as the additional hardware is becoming cost effective. A new method, based on how users perform an action, such as their gait

when walking, or typing patterns has emerged as a source of a personal “signature”. While not directly embedded into systems as yet, this is an option that will be coming in the future.

While the three main approaches to authentication appear to be easy to understand and in most cases easy to implement, authentication is not to be taken lightly, since it is such an important component of security. Potential attackers are constantly searching for ways to get past the system’s authentication mechanism, and they have employed some fairly ingenious methods to do so. Consequently, security professionals are constantly devising new methods, building on these three basic approaches, to provide authentication mechanisms for computer systems and networks.

Basic Authentication Basic authentication is the simplest technique used to manage access control across HTTP. Basic authentication operates by passing information encoded in Base64 form using standard HTTP headers. This is a plaintext method without any pretense of security. Figure 11.15 illustrates the operation of basic authentication.

• Figure 11.15 How basic authentication operates

Digest Authentication Digest authentication is a method used to negotiate credentials across the Web. Digest authentication uses hash functions and a nonce to improve security over basic authentication. Digest authentication works as follows, as illustrated in Figure 11.16:

• Figure 11.16 How digest authentication operates

1. The client requests login. 2. The server responds with a challenge and provides a nonce. 3. The client hashes the password and nonce. 4. The client returns the hashed password to the server.

5. The server requests the password from a password store. 6. The server hashes the password and nonce. 7. If both hashes match, login is granted. Digest authentication, although it improves security over basic

authentication, does not provide any significant level of security. Passwords are not sent in the clear. Digest authentication is subject to man-in-the-middle attacks and potentially replay attacks.

Exam Tip: The bottom line for both basic and digest authentication is that these are insecure methods and should not be relied upon for any level of security.

Kerberos Developed as part of MIT’s project Athena, Kerberos is a network authentication protocol designed for a client/server environment. The current version is Kerberos 5 release 1.13.2 and is supported by all major operating systems. Kerberos securely passes a symmetric key over an insecure network using the Needham-Schroeder symmetric key protocol. Kerberos is built around the idea of a trusted third party, termed a key distribution center (KDC), which consists of two logically separate parts: an authentication server (AS) and a ticket-granting server (TGS). Kerberos communicates via “tickets” that serve to prove the identity of users.

Exam Tip: Two tickets are used in Kerberos. The first is a ticket-granting ticket (TGT) obtained from the authentication server (AS). The TGT is presented to a ticket-granting server (TGS) when access to a server is requested and a client-to-server ticket is issued, granting access to the server. Typically both the AS and the TGS are logically separate parts of the key distribution center

(KDC).

Taking its name from the three-headed dog of Greek mythology, Kerberos is designed to work across the Internet, an inherently insecure environment. Kerberos uses strong encryption so that a client can prove its identity to a server and the server can in turn authenticate itself to the client. A complete Kerberos environment is referred to as a Kerberos realm. The Kerberos server contains user IDs and hashed passwords for all users that will have authorizations to realm services. The Kerberos server also has shared secret keys with every server to which it will grant access tickets. The basis for authentication in a Kerberos environment is the ticket.

Tickets are used in a two-step process with the client. The first ticket is a ticket-granting ticket (TGT) issued by the AS to a requesting client. The client can then present this ticket to the Kerberos server with a request for a ticket to access a specific server. This client-to-server ticket (also called a service ticket) is used to gain access to a server’s service in the realm. Since the entire session can be encrypted, this eliminates the inherently insecure transmission of items such as a password that can be intercepted on the network. Tickets are time-stamped and have a lifetime, so attempting to reuse a ticket will not be successful. Figure 11.17 details Kerberos operations.

• Figure 11.17 Kerberos operations

Tech Tip

Kerberos Authentication Kerberos is a third-party authentication service that uses a series of tickets as tokens for authenticating users. The six steps involved are protected using strong cryptography:

The user presents his credentials and requests a ticket from the key distribution center (KDC).

The KDC verifies credentials and issues a ticket-granting ticket (TGT).

The user presents a TGT and request for service to the KDC. The KDC verifies authorization and issues a client-to-server ticket (or service ticket).

The user presents a request and a client-to-server ticket to the desired service. If the client-to-server ticket is valid, service is granted to the client.

To illustrate how the Kerberos authentication service works, think about the common driver’s license. You have received a license that you can present to other entities to prove you are who you claim to be. Because other entities trust the state in which the license was issued, they will accept your license as proof of your identity. The state in which the license was issued is analogous to the Kerberos authentication service realm, and the license acts as a client-to-server ticket. It is the trusted entity both sides rely on to provide valid identifications. This analogy is not perfect, because we all probably have heard of individuals who obtained a phony driver’s license, but it serves to illustrate the basic idea behind Kerberos.

Certificates Certificates are a method of establishing authenticity of specific objects such as an individual’s public key or downloaded software. A digital certificate is a digital file that is sent as an attachment to a message and is

used to verify that the message did indeed come from the entity it claims to have come from. Digital certificates are covered in detail in Chapter 6.

Cross Check Digital Certificates and Digital Signatures Kerberos uses tickets to convey messages. Part of the ticket is a certificate that contains the requisite keys. Understanding how certificates convey this vital information is an important part of understanding how Kerberos-based authentication works. Certificates and how they are used was covered in Chapter 6, with the protocols associated with PKI covered in Chapter 7. Refer back to these chapters as needed.

Tokens A token is a hardware device that can be used in a challenge/response authentication process. In this way, it functions as both a something-you- have and something-you-know authentication mechanism. Several variations on this type of device exist, but they all work on the same basic principles. Tokens were described earlier in the chapter, and are commonly employed in remote authentication schemes as they provide additional surety of the identity of the user, even users who are somewhere else and cannot be observed.

Exam Tip: The use of a token is a common method of using “something you have” for authentication. A token can hold a cryptographic key or act as a one-time password (OTP) generator. It can also be a smart card that holds a cryptographic key (examples include the U.S. military Common Access Card and the Federal Personal Identity Verification [PIV] card). These devices can be safeguarded using a PIN and lockout mechanism to prevent use if stolen.

Multifactor Multifactor authentication is a term that describes the use of more than one authentication mechanism at the same time. An example of this is the

hardware token, which requires both a personal ID number (PIN) or password and the device itself to determine the correct response in order to authenticate to the system. This means that both the something-you-have and something-you-know mechanisms are used as factors in verifying authenticity of the user. Biometrics are also often used in conjunction with a PIN so that they, too, can be used as part of a multifactor authentication scheme, in this case something you are as well as something you know. The purpose of multifactor authentication is to increase the level of security, since more than one mechanism would have to be spoofed in order for an unauthorized individual to gain access to a computer system or network. The most common example of multifactor security is the common ATM card most of us carry in our wallets. The card is associated with a PIN that only the authorized cardholder should know. Knowing the PIN without having the card is useless, just as having the card without knowing the PIN will also not provide you access to your account.

Exam Tip: The required use of more than one authentication system is known as multifactor authentication. The most common example is the combination of a password with a hardware token. For high security, three factors can be used: password, token, and biometric.

Multifactor authentication is sometimes referred to as two-factor authentication or three-factor authentication, referring to the number of different factors used. It is important to note that this implies separate factors for the authentication element; a user ID and password are not two factors, as the user ID is not a shared secret element.

Mutual Authentication Mutual authentication describes a process in which each side of an electronic communication verifies the authenticity of the other. We are accustomed to the idea of having to authenticate ourselves to our ISP before we access the Internet, generally through the use of a user

ID/password pair, but how do we actually know that we are really communicating with our ISP and not some other system that has somehow inserted itself into our communication (a man-in-the-middle attack)? Mutual authentication provides a mechanism for each side of a client/server relationship to verify the authenticity of the other to address this issue. A common method of performing mutual authentication involves using a secure connection, such as Transport Layer Security (TLS), to the server and a one-time password generator that then authenticates the client.

Mutual TLS–based authentication provides the same functions as normal TLS, with the addition of authentication and nonrepudiation of the client. This second authentication, the authentication of the client, is done in the same manner as the normal server authentication using digital signatures. The client authentication represents the many sides of a many-to-one relationship. Mutual TLS authentication is not commonly used because of the complexity, cost, and logistics associated with managing the multitude of client certificates. This reduces the effectiveness, and most web applications are not designed to require client-side certificates.

Authorization Authorization is the process of permitting or denying access to a specific resource. Once identity is confirmed via authentication, specific actions can be authorized or denied. Many types of authorization schemes are used, but the purpose is the same: determine whether a given user who has been identified has permissions for a particular object or resource being requested. This functionality is frequently part of the operating system and is transparent to users. The separation of tasks, from identification to authentication to

authorization, has several advantages. Many methods can be used to perform each task, and on many systems several methods are concurrently present for each task. Separation of these tasks into individual elements allows combinations of implementations to work together. Any system or

resource, be it hardware (router or workstation) or a software component (database system), that requires authorization can use its own authorization method once authentication has occurred. This makes for efficient and consistent application of these principles.

Access Control The term access control has been used to describe a variety of protection schemes. It sometimes refers to all security features used to prevent unauthorized access to a computer system or network—or even a network resource such as a printer. In this sense, it may be confused with authentication. More properly, access is the ability of a subject (such as an individual or a process running on a computer system) to interact with an object (such as a file or hardware device). Once the individual has verified their identity, access controls regulate what the individual can actually do on the system. Just because a person is granted entry to the system, that does not mean that they should have access to all data the system contains.

Tech Tip

Access Control vs. Authentication It may seem that access control and authentication are two ways to describe the same protection mechanism. This, however, is not the case. Authentication provides a way to verify to the computer who the user is. Once the user has been authenticated, the access controls decide what operations the user can perform. The two go hand-in-hand but are not the same thing.

Remote Access Methods When a user requires access to a remote system, the process of remote access is used to determine the appropriate controls. This is done through a series of protocols and processes described in the remainder of this

chapter.

IEEE 802.1X IEEE 802.1X is an authentication standard that supports port-based authentication services between a user and an authorization device, such as an edge router. IEEE 802.1X is used by all types of networks, including Ethernet, Token Ring, and wireless. This standard describes methods used to authenticate a user prior to granting access to a network and the authentication server, such as a RADIUS server. 802.1X acts through an intermediate device, such as an edge switch, enabling ports to carry normal traffic if the connection is properly authenticated. This prevents unauthorized clients from accessing the publicly available ports on a switch, keeping unauthorized users out of a LAN. Until a client has successfully authenticated itself to the device, only Extensible Authentication Protocol over LAN (EAPOL) traffic is passed by the switch.

One security issue associated with 802.1X is that the authentication occurs only upon initial connection, and that another user can insert themselves into the connection by changing packets or using a hub. The secure solution is to pair 802.1X, which authenticates the initial connection, with a VPN or IPsec, which provides persistent security.

EAPOL is an encapsulated method of passing EAP messages over 802.1 frames. EAP is a general protocol that can support multiple methods of authentication, including one-time passwords, Kerberos, public keys, and security device methods such as smart cards. Once a client successfully authenticates itself to the 802.1X device, the switch opens ports for normal traffic. At this point, the client can communicate with the system’s AAA method, such as a RADIUS server, and authenticate itself to the network.

Wireless Protocols 802.1X is commonly used on wireless access points as a port-based authentication service prior to admission to the wireless network. 802.1X over wireless uses either 802.11i or EAP-based protocols, such as EAP- TLS or PEAP-TLS.

Cross Check Wireless Remote Access Wireless is a common method of allowing remote access to a network, as it does not require physical cabling and allows mobile connections. Wireless security, including protocols such as 802.11i and EAP-based solutions, is covered in Chapter 12.

RADIUS Remote Authentication Dial-In User Service (RADIUS) is an AAA protocol. It was submitted to the Internet Engineering Task Force (IETF) as a series of RFCs: RFC 2058 (RADIUS specification), RFC 2059 (RADIUS accounting standard), and updated RFCs 2865–2869, which are now standard protocols. RADIUS is designed as a connectionless protocol that uses the User

Datagram Protocol (UDP) as its transport layer protocol. Connection type issues, such as timeouts, are handled by the RADIUS application instead of the transport layer. RADIUS utilizes UDP port 1812 for authentication and authorization and UDP 1813 for accounting functions. RADIUS is a client/server protocol. The RADIUS client is typically a

network access server (NAS). Network access servers act as intermediaries, authenticating clients before allowing them access to a network. RADIUS, RRAS (Microsoft), RAS, and VPN servers can all act as network access servers. The RADIUS server is a process or daemon running on a UNIX or Windows Server machine. Communications between a RADIUS client and RADIUS server are encrypted using a

shared secret that is manually configured into each entity and not shared over a connection. Hence, communications between a RADIUS client (typically a NAS) and a RADIUS server are secure, but the communications between a user (typically a PC) and the RADIUS client are subject to compromise. This is important to note, for if the user’s machine (the PC) is not the RADIUS client (the NAS), then communications between the PC and the NAS are typically not encrypted and are passed in the clear.

RADIUS Authentication The RADIUS protocol is designed to allow a RADIUS server to support a wide variety of methods to authenticate a user. When the server is given a username and password, it can support Point-to-Point Protocol (PPP), Password Authentication Protocol (PAP), Challenge-Handshake Authentication Protocol (CHAP), UNIX login, and other mechanisms, depending on what was established when the server was set up. A user login authentication consists of a query (Access-Request) from the RADIUS client and a corresponding response (Access-Accept, Access- Challenge, or Access-Reject) from the RADIUS server, as you can see in Figure 11.18. The Access-Challenge response is the initiation of a challenge/response handshake. If the client cannot support challenge/response, then it treats the Challenge message as an Access- Reject.

• Figure 11.18 RADIUS communication sequence

The Access-Request message contains the username, encrypted password, NAS IP address, and port. The message also contains information concerning the type of session the user wants to initiate. Once the RADIUS server receives this information, it searches its database for a match on the username. If a match is not found, either a default profile is loaded or an Access-Reject reply is sent to the user. If the entry is found or the default profile is used, the next phase involves authorization, for in RADIUS, these steps are performed in sequence. Figure 11.18 shows the interaction between a user and the RADIUS client and RADIUS server and the steps taken to make a connection.

RADIUS Authorization In the RADIUS protocol, the authentication and authorization steps are performed together in response to a single Access-Request message, although they are sequential steps (see Figure 11.18). Once an identity has been established, either known or default, the authorization process determines what parameters are returned to the client. Typical authorization parameters include the service type allowed (shell or framed), the protocols allowed, the IP address to assign to the user (static or dynamic), and the access list to apply or static route to place in the NAS routing table.

Tech Tip

Shell Accounts Shell account requests are those that desire command-line access to a server. Once authentication is successfully performed, the client is connected directly to the server so command-line access can occur. Rather than being given a direct IP address on the network, the NAS acts as a pass-through device conveying access.

These parameters are all defined in the configuration information on the RADIUS client and server during setup. Using this information, the RADIUS server returns an Access-Accept message with these parameters to the RADIUS client.

RADIUS Accounting The RADIUS accounting function is performed independently of RADIUS authentication and authorization. The accounting function uses a separate UDP port, 1813 (see Table 11.2 in the “Connection Summary” section at the end of the chapter). The primary functionality of RADIUS accounting was established to support ISPs in their user accounting, and it supports typical accounting functions for time billing and security logging. The RADIUS accounting functions are designed to allow data to be transmitted at the beginning and end of a session, and they can indicate resource utilization, such as time, bandwidth, and so on.

Table 11.2 Common TCP/UDP Remote Access Networking Port Assignments

Diameter Diameter is the name of an AAA protocol suite, designated by the IETF to replace the aging RADIUS protocol. Diameter operates in much the same way as RADIUS in a client/server configuration, but it improves upon RADIUS, resolving discovered weaknesses. Diameter is a TCP-based

service and has more extensive AAA capabilities. Diameter is also designed for all types of remote access, not just modem pools. As more and more users adopt broadband and other connection methods, these newer services require more options to determine permissible usage properly and to account for and log the usage. Diameter is designed with these needs in mind. Diameter also has an improved method of encrypting message

exchanges to prohibit replay and man-in-the-middle attacks. Taken all together, Diameter, with its enhanced functionality and security, is an improvement on the proven design of the old RADIUS standard.

TACACS+ The Terminal Access Controller Access Control System+ (TACACS+) protocol is the current generation of the TACACS family. Originally TACACS was developed by BBN Planet Corporation for MILNET, an early military network, but it has been enhanced by Cisco, which has expanded its functionality twice. The original BBN TACACS system provided a combination process of authentication and authorization. Cisco extended this to Extended Terminal Access Controller Access Control System (XTACACS), which provided for separate authentication, authorization, and accounting processes. The current generation, TACACS+, has extended attribute control and accounting processes. One of the fundamental design aspects is the separation of

authentication, authorization, and accounting in this protocol. Although there is a straightforward lineage of these protocols from the original TACACS, TACACS+ is a major revision and is not backward-compatible with previous versions of the protocol series. TACACS+ uses TCP as its transport protocol, typically operating over

TCP port 49. This port is used for the login process and is reserved in RFC 3232, “Assigned Numbers,” manifested in a database from the Internet Assigned Numbers Authority (IANA). In the IANA specification, both UDP port 49 and TCP port 49 are reserved for the TACACS+ login host

protocol (see Table 11.2 in the “Connection Summary” section at the end of the chapter). TACACS+ is a client/server protocol, with the client typically being a

NAS and the server being a daemon process on a UNIX, Linux, or Windows server. This is important to note, for if the user’s machine (usually a PC) is not the client (usually a NAS), then communications between PC and NAS are typically not encrypted and are passed in the clear. Communications between a TACACS+ client and TACACS+ server are encrypted using a shared secret that is manually configured into each entity and is not shared over a connection. Hence, communications between a TACACS+ client (typically a NAS) and a TACACS+ server are secure, but the communications between a user (typically a PC) and the TACACS+ client are subject to compromise.

TACACS+ Authentication TACACS+ allows for arbitrary length and content in the authentication exchange sequence, enabling many different authentication mechanisms to be used with TACACS+ clients. Authentication is optional and is determined as a site-configurable option. When authentication is used, common forms include PPP PAP, PPP CHAP, PPP EAP, token cards, and Kerberos. The authentication process is performed using three different packet types: START, CONTINUE, and REPLY. START and CONTINUE packets originate from the client and are directed to the TACACS+ server. The REPLY packet is used to communicate from the TACACS+ server to the client. The authentication process is illustrated in Figure 11.19, and it begins

with a START message from the client to the server. This message may be in response to an initiation from a PC connected to the TACACS+ client. The START message describes the type of authentication being requested (simple plaintext password, PAP, CHAP, and so on). This START message may also contain additional authentication data, such as a username and password. A START message is also sent as a response to a restart request from the server in a REPLY message. A START message

always has its sequence number set to 1.

• Figure 11.19 TACACS+ communication sequence

When a TACACS+ server receives a START message, it sends a REPLY message. This REPLY message indicates whether the authentication is complete or needs to be continued. If the process needs to be continued, the REPLY message also specifies what additional information is needed. The response from a client to a REPLY message requesting additional data is a CONTINUE message. This process continues until the server has all the information needed, and the authentication process concludes with a success or failure.

TACACS+ Authorization Authorization is defined as the granting of specific permissions based on the privileges held by the account. This generally occurs after authentication, as shown in Figure 11.19, but this is not a firm requirement. A default state of “unknown user” exists before a user is authenticated, and permissions can be determined for an unknown user. As with authentication, authorization is an optional process and may or may not be part of a site-specific operation. When it is used in conjunction with authentication, the authorization process follows the authentication process and uses the confirmed user identity as input in the decision process. The authorization process is performed using two message types:

REQUEST and RESPONSE. The authorization process is performed using an authorization session consisting of a single pair of REQUEST and RESPONSE messages. The client issues an authorization REQUEST message containing a fixed set of fields enumerating the authenticity of the user or process requesting permission and a variable set of fields enumerating the services or options for which authorization is being requested. The RESPONSE message in TACACS+ is not a simple yes or no; it can

also include qualifying information, such as a user time limit or IP restrictions. These limitations have important uses, such as enforcing time

limits on shell access or enforcing IP access list restrictions for specific user accounts.

TACACS+ Accounting As with the two previous services, accounting is also an optional function of TACACS+. When utilized, it typically follows the other services. Accounting in TACACS+ is defined as the process of recording what a user or process has done. Accounting can serve two important purposes:

It can be used to account for services being utilized, possibly for billing purposes.

It can be used for generating security audit trails.

TACACS+ accounting records contain several pieces of information to support these tasks. The accounting process has the information revealed in the authorization and authentication processes, so it can record specific requests by user or process. To support this functionality, TACACS+ has three types of accounting records: START, STOP, and UPDATE. Note that these are record types, not message types as earlier discussed.

Authentication Protocols Numerous authentication protocols have been developed, used, and discarded in the brief history of computing. Some have come and gone because they did not enjoy market share, others have had security issues, and yet others have been revised and improved in newer versions. Although it’s impossible and impractical to cover them all, some of the common ones follow.

L2TP and PPTP Layer 2 Tunneling Protocol (L2TP) and Point-to-Point Tunneling Protocol (PPTP) are both OSI Layer 2 tunneling protocols. Tunneling is the encapsulation of one packet within another, which allows you to hide the

original packet from view or change the nature of the network transport. This can be done for both security and practical reasons. From a practical perspective, assume that you are using TCP/IP to

communicate between two machines. Your message may pass over various networks, such as an Asynchronous Transfer Mode (ATM) network, as it moves from source to destination. As the ATM protocol can neither read nor understand TCP/IP packets, something must be done to make them passable across the network. By encapsulating a packet as the payload in a separate protocol, so it can be carried across a section of a network, a mechanism called a tunnel is created. At each end of the tunnel, called the tunnel endpoints, the payload packet is read and understood. As it goes into the tunnel, you can envision your packet being placed in an envelope with the address of the appropriate tunnel endpoint on the envelope. When the envelope arrives at the tunnel endpoint, the original message (the tunnel packet’s payload) is re-created, read, and sent to its appropriate next stop. The information being tunneled is understood only at the tunnel endpoints; it is not relevant to intermediate tunnel points because it is only a payload.

PPP Point-to-Point Protocol (PPP) is an older, still widely used protocol for establishing dial-in connections over serial lines or Integrated Services Digital Network (ISDN) services. PPP has several authentication mechanisms, including PAP, CHAP, and the Extensible Authentication Protocol (EAP). These protocols are used to authenticate the peer device, not a user of the system. PPP is a standardized Internet encapsulation of IP traffic over point-to-point links, such as serial lines. The authentication process is performed only when the link is established.

Tech Tip

PPP Functions and Authentication

PPP supports three functions:

Encapsulate datagrams across serial links

Establish, configure, and test links using LCP Establish and configure different network protocols using NCP

PPP supports two authentication protocols:

Password Authentication Protocol (PAP)

Challenge-Handshake Authentication Protocol (CHAP)

PPTP Microsoft led a consortium of networking companies to extend PPP to enable the creation of virtual private networks (VPNs). The result was the Point-to-Point Tunneling (PPTP), a network protocol that enables the secure transfer of data from a remote PC to a server by creating a VPN across a TCP/IP network. This remote network connection can also span a public switched telephone network (PSTN) and is thus an economical way of connecting remote dial-in users to a corporate data network. The incorporation of PPTP into the Microsoft Windows product line provides a built-in secure method of remote connection using the operating system, and this has given PPTP a large marketplace footprint. For most PPTP implementations, three computers are involved: the

PPTP client, the NAS, and a PPTP server, as shown in Figure 11.20. The connection between the remote client and the network is established in stages, as illustrated in Figure 11.21. First the client makes a PPP connection to a NAS, typically an ISP. (In today’s world of widely available broadband, if there is already an Internet connection, then there is no need to perform the PPP connection to the ISP.) Once the PPP connection is established, a second connection is made over the PPP connection to the PPTP server. This second connection creates the VPN connection between the remote client and the PPTP server. A typical VPN connection is one in which the user is in a hotel with a wireless Internet connection, connecting to a corporate network. This connection acts as a

tunnel for future data transfers. Although these diagrams illustrate a telephone connection, this first link can be virtually any method. Common in hotels today are wired connections to the Internet. These wired connections typically are provided by a local ISP and offer the same services as a phone connection, albeit at a much higher data transfer rate.

• Figure 11.20 PPTP communication diagram

• Figure 11.21 PPTP message encapsulation during transmission

PPTP establishes a tunnel from the remote PPTP client to the PPTP server and enables encryption within this tunnel. This provides a secure method of transport. To do this and still enable routing, an intermediate addressing scheme, Generic Routing Encapsulation (GRE), is used. To establish the connection, PPTP uses communications across TCP

port 1723 (see Table 11.2 in the “Connection Summary” section at the end of the chapter), so this port must remain open across the network firewalls for PPTP to be initiated. Although PPTP allows the use of any PPP

authentication scheme, CHAP is used when encryption is specified, to provide an appropriate level of security. For the encryption methodology, Microsoft chose the RSA RC4 cipher, with either a 40- or 128-bit session key length, and this is OS driven. Microsoft Point-to-Point Encryption (MPPE) is an extension to PPP that enables VPNs to use PPTP as the tunneling protocol.

EAP Extensible Authentication Protocol (EAP) is a universal authentication framework defined by RFC 3748 that is frequently used in wireless networks and point-to-point connections. Although EAP is not limited to wireless and can be used for wired authentication, it is most often used in wireless LANs. EAP is discussed in detail in Chapter 12.

CHAP Challenge-Handshake Authentication Protocol (CHAP) is used to provide authentication across a point-to-point link using PPP. In this protocol, authentication after the link has been established is not mandatory. CHAP is designed to provide authentication periodically through the use of a challenge/response system that is sometimes described as a three-way handshake, as illustrated in Figure 11.22. The initial challenge (a randomly generated number) is sent to the client. The client uses a one-way hashing function to calculate what the response should be and then sends this back. The server compares the response to what it calculated the response should be. If they match, communication continues. If the two values don’t match, then the connection is terminated. This mechanism relies on a shared secret between the two entities so that the correct values can be calculated. Microsoft has created two versions of CHAP, modified to increase the usability of CHAP across Microsoft’s product line. MSCHAP v1, defined in RFC 2433, has been deprecated and was dropped in Windows Vista. The current standard, version 2, defined in RFC 2759, was introduced with Windows 2000.

• Figure 11.22 The CHAP challenge/response sequence

NTLM NT LAN Manager (NTLM) is an authentication protocol designed by Microsoft, for use with the Server Message Block (SMB) protocol. SMB is an application-level network protocol primarily used for sharing of files and printers in Windows-based networks. NTLM was designed as a replacement for the LANMAN protocol. The current version is NTLM v2, which was introduced with Windows NT 4.0 SP4. Although Microsoft has adopted the Kerberos protocol for authentication, NTLM v2 is still used when

Authenticating to a server using an IP address

Authenticating to a server that belongs to a different Active Directory forest

Authenticating to a server that doesn’t belong to a domain

No Active Directory domain exists (“workgroup” or “peer-to-peer” connection)

PAP Password Authentication Protocol (PAP) involves a two-way handshake in

which the username and password are sent across the link in cleartext. PAP authentication does not provide any protection against playback and line sniffing. PAP is now a deprecated standard.

L2TP Layer 2 Tunneling Protocol (L2TP) is also an Internet standard and came from the Layer 2 Forwarding (L2F) protocol, a Cisco initiative designed to address issues with PPTP. Whereas PPTP is designed around PPP and IP networks, L2F, and hence L2TP, is designed for use across all kinds of networks, including ATM and Frame Relay. Additionally, whereas PPTP is designed to be implemented in software at the client device, L2TP was conceived as a hardware implementation using a router or a special-purpose appliance. L2TP can be configured in software and is in Microsoft’s RRAS servers, which use L2TP to create a VPN. L2TP works in much the same way as PPTP, but it opens up several

items for expansion. For instance, in L2TP, routers can be enabled to concentrate VPN traffic over higher-bandwidth lines, creating hierarchical networks of VPN traffic that can be more efficiently managed across an enterprise. L2TP also has the ability to use IPsec and Data Encryption Standard (DES) as encryption protocols, providing a higher level of data security. L2TP is also designed to work with established AAA services such as RADIUS and TACACS+ to aid in user authentication, authorization, and accounting. L2TP is established via UDP port 1701, so this is an essential port to

leave open across firewalls supporting L2TP traffic. Microsoft supports L2TP in Windows 2000 and above, but because of the computing power required, most implementations will use specialized hardware (such as a Cisco router).

Telnet One of the methods to grant remote access to a system is through Telnet. Telnet is the standard terminal-emulation protocol within the TCP/IP

protocol series, and it is defined in RFC 854. Telnet allows users to log in remotely and access resources as if the user had a local terminal connection. Telnet is an old protocol and offers little security. Information, including account names and passwords, is passed in cleartext over the TCP/IP connection.

Exam Tip: Telnet uses TCP port 23. Be sure to memorize the common ports used by common services for the exam.

Telnet makes its connection using TCP port 23. As Telnet is implemented on most products using TCP/IP, it is important to control access to Telnet on machines and routers when setting them up. Failure to control access by using firewalls, access lists, and other security methods, or even by disabling the Telnet daemon, is equivalent to leaving an open door for unauthorized users on a system.

SSH Secure Shell (SSH) is a protocol series designed to facilitate secure network functions across an insecure network. SSH provides direct support for secure remote login, secure file transfer, and secure forwarding of TCP/IP and X Window System traffic. An SSH connection is an encrypted channel, providing for confidentiality and integrity protection. SSH has its origins as a replacement for the insecure Telnet application

from the UNIX operating system. An original component of UNIX, Telnet allowed users to connect between systems. Although Telnet is still used today, it has some drawbacks, as discussed in the preceding section. Some enterprising University of California, Berkeley, students subsequently developed the r- commands, such as rlogin, to permit access based on the user and source system, as opposed to passing passwords. This was not perfect either, however, because when a login was required, it was still passed in the clear. This led to the development of the SSH protocol series,

designed to eliminate all of the insecurities associated with Telnet, r- commands, and other means of remote access.

Exam Tip: SSH uses TCP port 22. SCP (secure copy) and SFTP (secure FTP) use SSH, so each also uses TCP port 22.

SSH opens a secure transport channel between machines by using an SSH daemon on each end. These daemons initiate contact over TCP port 22 and then communicate over higher ports in a secure mode. One of the strengths of SSH is its support for many different encryption protocols. SSH 1.0 started with RSA algorithms, but at the time they were still under patent, and this led to SSH 2.0 with extended support for Triple DES (3DES) and other encryption methods. Today, SSH can be used with a wide range of encryption protocols, including RSA, 3DES, Blowfish, International Data Encryption Algorithm (IDEA), CAST128, AES256, and others. The SSH protocol has facilities to encrypt data automatically, provide

authentication, and compress data in transit. It can support strong encryption, cryptographic host authentication, and integrity protection. The authentication services are host-based and not user-based. If user authentication is desired in a system, it must be set up separately at a higher level in the OSI model. The protocol is designed to be flexible and simple, and it is designed specifically to minimize the number of round- trips between systems. The key exchange, public key, symmetric key, message authentication, and hash algorithms are all negotiated at connection time. Individual data-packet integrity is assured through the use of a message authentication code that is computed from a shared secret, the contents of the packet, and the packet sequence number. The SSH protocol consists of three major components:

Transport layer protocol Provides server authentication,

confidentiality, integrity, and compression

User authentication protocol Authenticates the client to the server Connection protocol Provides multiplexing of the encrypted tunnel into several logical channels

SSH is very popular in the UNIX environment, and it is actively used as a method of establishing VPNs across public networks. Because all communications between the two machines are encrypted at the OSI application layer by the two SSH daemons, this leads to the ability to build very secure solutions and even solutions that defy the ability of outside services to monitor. As SSH is a standard protocol series with connection parameters established via TCP port 22, different vendors can build differing solutions that can still interoperate.

Tech Tip

RDP Remote Desktop Protocol (RDP) is a proprietary Microsoft protocol designed to provide a graphical connection to another computer. The computer requesting the connection has RDP client software (built into Windows), and the target uses an RDP server. This software has been available for many versions of Windows and was formerly called Terminal Services. Client and server versions also exist for Linux platforms. RDP uses TCP and UDP ports 3389, so if RDP is desired, these ports need to be open on the firewall.

Although Windows Server implementations of SSH exist, this has not been a popular protocol in the Windows environment from a server perspective. The development of a wide array of commercial SSH clients for the Windows platform indicates the marketplace strength of interconnection from desktop PCs to UNIX-based servers utilizing this protocol.

FTP/FTPS/SFTP

One of the methods of transferring files between machines is through the use of the File Transfer Protocol (FTP). FTP is a plaintext protocol that operates by communicating over TCP between a client and a server. The client initiates a transfer with an FTP request to the server’s TCP port 21. This is the control connection, and this connection remains open over the duration of the file transfer. The actual data transfer occurs on a negotiated data transfer port, typically a high-order port number. FTP was not designed to be a secure method of transferring files. If a secure method is desired, then using FTPS or SFTP is best. FTPS is the use of FTP over an SSL/TLS secured channel. This can be

done either in explicit mode, where an AUTH TLS command is issued, or in implicit mode, where the transfer occurs over TCP port 990 for the control channel and TCP port 989 for the data channel. SFTP is not FTP per se, but rather a completely separate Secure File Transfer Protocol as defined by an IETF Draft, the latest of which, version 6, expired in July 2007, but has been incorporated into products in the marketplace.

Exam Tip: FTP uses TCP port 21 as a control channel and TCP port 20 as a typical active mode data port, as some firewalls are set to block ports above 1024.

It is also possible to run FTP over SSH, as later versions of SSH allow securing of channels such as the FTP control channel; this has also been referred to as Secure FTP. This leaves the data channel unencrypted, a problem that has been solved in version 3.0 of SSH, which supports FTP commands. The challenge of encrypting the FTP data communications is that the mutual port agreement must be opened on the firewall, and for security reasons, high-order ports that are not explicitly defined are typically secured. Because of this challenge, Secure Copy (SCP) is often a more desirable alternative to SFTP when using SSH.

VPNs A virtual private network (VPN) is a secure virtual network built on top of a physical network. The security of a VPN lies in the encryption of packet contents between the endpoints that define the VPN. The physical network upon which a VPN is built is typically a public network, such as the Internet. Because the packet contents between VPN endpoints are encrypted, to an outside observer on the public network, the communication is secure, and depending on how the VPN is set up, security can even extend to the two communicating parties’ machines. Virtual private networking is not a protocol per se, but rather a method

of using protocols to achieve a specific objective—secure communications —as shown in Figure 11.23. A user who wants to have a secure communication channel with a server across a public network can set up two intermediary devices, VPN endpoints, to accomplish this task. The user can communicate with his endpoint, and the server can communicate with its endpoint. The two endpoints then communicate across the public network. VPN endpoints can be software solutions, routers, or specific servers set up for specific functionality. This implies that VPN services are set up in advance and are not something negotiated on-the-fly.

• Figure 11.23 VPN service over an Internet connection

A typical use of VPN services is a user accessing a corporate data network from a home PC across the Internet. The employee installs VPN software from work on a home PC. This software is already configured to communicate with the corporate network’s VPN endpoint; it knows the location, the protocols that will be used, and so on. When the home user wants to connect to the corporate network, she connects to the Internet and then starts the VPN software. The user can then log into the corporate network by using an appropriate authentication and authorization methodology. The sole purpose of the VPN connection is to provide a private connection between the machines, which encrypts any data sent between the home user’s PC and the corporate network. Identification, authorization, and all other standard functions are accomplished with the standard mechanisms for the established system. VPNs can use many different protocols to offer a secure method of

communicating between endpoints. Common methods of encryption on

VPNs include PPTP, IPsec, SSH, and L2TP, all of which are discussed in this chapter. The key is that both endpoints know the protocol and share a secret. All of this necessary information is established when the VPN is set up. At the time of use, the VPN only acts as a private tunnel between the two points and does not constitute a complete security solution.

IPsec Internet Protocol Security (IPsec) is a set of protocols developed by the IETF to securely exchange packets at the network layer (Layer 3) of the OSI model (RFCs 2401–2412). Although these protocols work only in conjunction with IP networks, once an IPsec connection is established, it is possible to tunnel across other networks at lower levels of the OSI model. The set of security services provided by IPsec occurs at the network layer of the OSI model, so higher-layer protocols, such as TCP, UDP, Internet Control Message Protocol (ICMP), Border Gateway Protocol (BGP), and the like, are not functionally altered by the implementation of IPsec services. The IPsec protocol series has a sweeping array of services it is designed

to provide, including but not limited to access control, connectionless integrity, traffic-flow confidentiality, rejection of replayed packets, data security (encryption), and data-origin authentication. IPsec has two defined methods—transport and tunneling—that provide different levels of security. IPsec also has three modes of connection: host-to-server, server- to-server, and host-to-host. The transport method encrypts only the data portion of a packet, thus

enabling an outsider to see source and destination IP addresses. The transport method protects the higher-level protocols associated with a packet and protects the data being transmitted but allows knowledge of the transmission itself. Protection of the data portion of a packet is referred to as content protection.

Exam Tip: In transport mode (end-to-end), security of packet traffic is provided by the endpoint computers. In tunnel mode (portal-to-portal), security of packet traffic is provided between endpoint node machines in each network and not at the terminal host machines.

Tunneling provides encryption of source and destination IP addresses, as well as of the data itself. This provides the greatest security, but it can be done only between IPsec servers (or routers) because the final destination needs to be known for delivery. Protection of the header information is known as context protection. It is possible to use both methods at the same time, such as using

transport within one’s own network to reach an IPsec server, which then tunnels to the target server’s network, connecting to an IPsec server there, and then using the transport method from the target network’s IPsec server to the target host.

Security Associations A security association (SA) is a formal manner of describing the necessary and sufficient portions of the IPsec protocol series to achieve a specific level of protection. Because many options exist, both communicating parties must agree on the use of the protocols that are available, and this agreement is referred to as a security association. SAs exist both for integrity-protecting systems and confidentiality-protecting systems. In each IPsec implementation, a security association database (SAD) defines parameters associated with each SA. The SA is a one-way (simplex) association, and if two-way communication security is desired, two SAs are used—one for each direction.

Exam Tip: A security association is a logical set of security parameters designed to facilitate the

sharing of information between entities.

IPsec Configurations Four basic configurations can be applied to machine-to-machine connections using IPsec. The simplest is a host-to-host connection between two machines, as shown in Figure 11.24. In this case, the Internet is not a part of the SA between the machines. If bidirectional security is desired, two SAs are used. The SAs are effective from host to host.

• Figure 11.24 A host-to-host connection between two machines

The second case places two security devices in the stream, relieving the hosts of the calculation and encapsulation duties. These two gateways have an SA between them. The network is assumed to be secure from each

machine to its gateway, and no IPsec is performed across these hops. Figure 11.25 shows the two security gateways with a tunnel across the Internet, although either tunnel or transport mode could be used.

• Figure 11.25 Two security gateways with a tunnel across the Internet

The third case combines the first two. A separate SA exists between the gateway devices, but an SA also exists between hosts. This could be considered a tunnel inside a tunnel, as shown in Figure 11.26.

• Figure 11.26 A tunnel inside a tunnel

Remote users commonly connect through the Internet to an organization’s network. The network has a security gateway through which it secures traffic to and from its servers and authorized users. In the last case, illustrated in Figure 11.27, the user establishes an SA with the security gateway and then a separate SA with the desired server, if required. This can be done using software on a remote laptop and hardware at the organization’s network.

• Figure 11.27 Tunnel from host to gateway

Windows can act as an IPsec server, as can routers and other servers. The primary issue is CPU usage and where the computing power should be implanted. This consideration has led to the rise of IPsec appliances, which are hardware devices that perform the IPsec function specifically for a series of communications. Depending on the number of connections, network bandwidth, and so on, these devices can be inexpensive for small office or home office use or quite expensive for large, enterprise-level implementations.

IPsec Security

IPsec uses two protocols to provide traffic security:

Authentication Header (AH) A header added to a packet for the purposes of integrity checking

Encapsulating Security Payload (ESP) A method of encrypting the data portion of a datagram to provide confidentiality

For key management and exchange, three protocols exist:

Internet Security Association and Key Management Protocol (ISAKMP)

Oakley Secure Key Exchange Mechanism for Internet (SKEMI)

These key management protocols can be collectively referred to as Internet Key Management Protocol (IKMP) or Internet Key Exchange (IKE). IPsec does not define specific security algorithms, nor does it require

specific methods of implementation. IPsec is an open framework that allows vendors to implement existing industry-standard algorithms suited for specific tasks. This flexibility is key in IPsec’s ability to offer a wide range of security functions. IPsec allows several security technologies to be combined into a comprehensive solution for network-based confidentiality, integrity, and authentication. IPsec uses the following:

Exam Tip: IPsec AH protects integrity, but it does not provide privacy. IPsec ESP provides confidentiality, but it does not protect integrity of the packet. To cover both privacy and integrity, both headers can be used at the same time.

Diffie-Hellman key exchange between peers on a public network

Public key signing of Diffie-Hellman key exchanges to guarantee identity and avoid man-in-the-middle attacks

Bulk encryption algorithms, such as IDEA and 3DES, for encrypting data

Keyed hash algorithms, such as HMAC, and traditional hash algorithms, such as MD5 and SHA-1, for packet-level authentication

Digital certificates to act as digital ID cards between parties

To provide traffic security, two header extensions have been defined for IP datagrams. The AH, when added to an IP datagram, ensures the integrity of the data and also the authenticity of the data’s origin. By protecting the nonchanging elements in the IP header, the AH protects the IP address, which enables data-origin authentication. The ESP provides security services for the higher-level protocol portion of the packet only, not the IP header. AH and ESP can be used separately or in combination, depending on the

level and types of security desired. Both also work with the transport and tunnel modes of IPsec protocols. In transport mode, the two communication endpoints provide security primarily for the upper-layer protocols. The cryptographic endpoints, where encryption and decryption occur, are located at the source and destination of the communication channel. When AH is in transport mode, the original IP header is exposed, but its contents are protected via the AH block in the packet, as illustrated in Figure 11.28. When AH is employed in tunnel mode, portions of the outer IP header are given the same header protection that occurs in transport mode, with the entire inner packet receiving protection. This is illustrated in Figure 11.29. The use of tunnel mode allows easier crossing of firewalls, for without it, specific firewall rules would be needed to pass the modified transport packet header.

• Figure 11.28 IPsec use of AH in transport mode

• Figure 11.29 IPsec use of AH in tunnel mode

Tunneling is a means of encapsulating packets inside a protocol that is understood only at the entry and exit points of the tunnel. This provides security during transport in the tunnel, because outside observers cannot

decipher packet contents or even the identities of the communicating parties. IPsec has a tunnel mode that can be used from server to server across a public network. Although the tunnel endpoints are referred to as servers, these devices can be routers, appliances, or servers. In tunnel mode, the tunnel endpoints merely encapsulate the entire packet with new IP headers to indicate the endpoints, and they encrypt the contents of this new packet. The true source and destination information is contained in the inner IP header, which is encrypted in the tunnel. The outer IP header contains the addresses of the endpoints of the tunnel. ESP provides a means of encrypting the packet’s contents, as shown in

Figure 11.30. In this case, in transport mode, the datagram contents are encrypted and authenticated via the ESP header and footer/trailer that are inserted into the datagram. As mentioned, AH and ESP can be employed in tunnel mode. ESP affords the same encryption protection to the contents of the tunneled packet, which is the entire packet from the initial sender, as illustrated in Figure 11.31. Together, in tunnel mode, AH and ESP can provide complete protection across the packet, as shown in Figure 11.32. The specific combination of AH and ESP is referred to as a security association in IPsec.

• Figure 11.30 IPsec use of ESP in transport mode

• Figure 11.31 IPsec use of ESP in tunnel mode

• Figure 11.32 IPsec ESP and AH packet construction in tunnel mode

In IP version 4 (IPv4), IPsec is an add-on, and its acceptance is vendor driven. It is not a part of the original IP—one of the short-sighted design flaws of the original IP. In IPv6, IPsec is integrated into IP and is native on all packets. Its use is still optional, but its inclusion in the protocol suite will guarantee interoperability across vendor solutions when they are compliant with IPv6 standards. IPsec uses cryptographic keys in its security process and has both

manual and automatic distribution of keys as part of the protocol series. Manual key distribution is included, but it is practical only in small, static environments and does not scale to enterprise-level implementations. The default method of key management, Internet Key Exchange (IKE), is automated. IKE authenticates each peer involved in IPsec and negotiates the security policy, including the exchange of session keys. IKE creates a secure tunnel between peers and then negotiates the security association

for IPsec across this channel. This is done in two phases: the first develops the channel, and the second develops the security association. Figure 11.33 illustrates the different levels of protection offered by

VPNs and IPsec. This shows the advantages of IPsec and its more comprehensive coverage.

• Figure 11.33 Protection from different levels of encryption

Vulnerabilities of Remote Access Methods

The primary vulnerability associated with many of these methods of remote access is the passing of critical data in cleartext. Plaintext passing of passwords provides no security if the password is sniffed, and sniffers are easy to use on a network. Even plaintext passing of user IDs gives away information that can be correlated and possibly used by an attacker. Plaintext credential passing is one of the fundamental flaws with Telnet and is why SSH was developed. This is also one of the flaws with RADIUS and TACACS+, as they have a segment unprotected. There are methods for overcoming these limitations, although they require discipline and understanding in setting up a system. The strength of the encryption algorithm is also a concern. Should a

specific algorithm or method prove to be vulnerable, services that rely solely on it are also vulnerable. To get around this dependency, many of the protocols allow numerous encryption methods, so that should one prove vulnerable, a shift to another restores security.

Tech Tip

IPsec in a Nutshell IPsec has two primary modes, transport mode and tunnel mode. Transport mode is simpler and adds fewer bytes to a packet, but can have issues transiting items such as firewalls. Tunneling mode resolves the firewall issue by total encapsulation. IPsec has two primary mechanisms, AH and ESP. AH provides for authentication of datagram contents, but no protection in the form of secrecy. ESP encrypts the datagram, providing secrecy, and when used with EH, ESP provides authentication as well.

As with any software implementation, there always exists the possibility that a bug could open the system to attack. Bugs have been corrected in most software packages to close holes that made systems vulnerable, and remote access functionality is no exception. This is not a Microsoft-only phenomenon, as one might believe from the popular press. Critical flaws have been found in almost every product, from open system implementations such as OpenSSH to proprietary systems such as Cisco

IOS. The important issue is not the presence of software bugs, for as software continues to become more complex, this is an unavoidable issue. The true key is vendor responsiveness to fixing the bugs once they are discovered, and the major players, such as Cisco and Microsoft, have been very responsive in this area.

Connection Summary There are many protocols used for remote access and authentication and related purposes. These methods have their own assigned ports and these assignments are summarized in Table 11.2.

Chapter 11 Review

For More Information Microsoft’s TechNet Group Policy page http://technet.microsoft.com/en- us/windowsserver/grouppolicy/default.aspx

SANS Consensus Policy Resource Community – Password Policy https://www.sans.org/security-resources/policies/general/pdf/password- protection-policy

Lab Manual Exercises The following lab exercises from the companion lab manual, Principles of Computer Security Lab Manual, Fourth Edition, provide practical application of material covered in this chapter:

Chapter Summary After reading this chapter and completing the exercises, you should understand the following about privilege management, authentication, and remote access protocols.

Identify the differences among user, group, and role management

Privilege management is the process of restricting a user’s ability to interact with the computer system.

Privilege management can be based on an individual user basis, on membership in a specific group or groups, or on a function/role.

Key concepts in privilege management are the ability to restrict and control access to information and information systems.

One of the methods used to simplify privilege management is single sign-on, which requires a user to authenticate successfully once. The validated credentials and associated rights and privileges are then automatically carried forward when the user accesses other systems or applications.

Implement password and domain password policies

Password policies are sets of rules that help users select, employ, and store strong passwords. Tokens combine “something you have” with “something you know,” such as a password or PIN, and can be hardware or software based.

Passwords should have a limited span and should expire on a scheduled basis.

Describe methods of account management (SSO, time of day, logical token, account expiration)

Administrators have many different tools at their disposal to control access to computer resources including password and account expiration methods.

User authentication methods can include several factors including tokens.

Users can be limited in the hours during which they can access resources.

Resources such as files, folders, and printers can be controlled through permissions or access control lists.

Permissions can be assigned based on a user’s identity or their membership in one or more groups.

Describe methods of access management (MAC, DAC, and RBAC)

Mandatory access control is based on the sensitivity of the information or process itself.

Discretionary access control uses file permissions and ACLs to restrict access based on a user’s identity or group membership.

Role-based access control restricts access based on the user’s assigned role or roles.

Rule-based access control restricts access based on a defined set of

rules established by the administrator.

Discuss the methods and protocols for remote access to networks

Remote access protocols provide a mechanism to remotely connect clients to networks.

A wide range of remote access protocols has evolved to support various security and authentication mechanisms.

Remote access is granted via remote access servers, such as RRAS or RADIUS.

Identify authentication, authorization, and accounting (AAA) protocols

Authentication is a cornerstone element of security, connecting access to a previously approved user ID.

Authorization is the process of determining whether an authenticated user has permission.

Accounting protocols manage connection time and cost records.

Explain authentication methods and the security implications in their use

Password-based authentication is still the most widely used because of cost and ubiquity.

Ticket-based systems, such as Kerberos, form the basis for most modern authentication and credentialing systems.

Implement virtual private networks (VPNs) and their security aspects

VPNs use protocols to establish a private network over a public network, shielding user communications from outside observation.

VPNs can be invoked via many different protocol mechanisms and

involve either a hardware or software client on each end of the communication channel.

Describe Internet Protocol Security (IPsec) and its use in securing communications

IPsec is the native method of securing IP packets; it is optional in IPv4 and mandatory in IPv6.

IPsec uses Authentication Headers (AH) to authenticate packets.

IPsec uses Encapsulating Security Payload (ESP) to provide confidentiality service at the datagram level.

Key Terms AAA (305) access control (311) access control list (ACL) (300) accounting (305) administrator (290) attribute-based access control (ABAC) (303) authentication (305) Authentication Header (AH) (41) authentication server (AS) (308) authorization (305) content protection (324) context protection (325) discretionary access control (DAC) (302) domain controller (293) domain password policy (293) Encapsulating Security Payload (ESP) (41) eXtensible Access Control Markup Language (XACML) (304)

group (291) group policy object (GPO) (293) identification (305) Internet Key Exchange (IKE) (329) Internet Protocol Security (IPsec) (324) Internet Security Association and Key Management Protocol

(ISAKMP) (41) Kerberos (308) key distribution center (KDC) (308) Layer 2 Tunneling Protocol (L2TP) (320) mandatory access control (MAC) (301) Oakley (41) password policy (292) permissions (290) Point-to-Point Tunneling Protocol (PPTP) (317) privilege management (288) privileges (288) remote access server (RAS) (305) rights (289) role (292) role-based access control (RBAC) (303) root (290) rule-based access control (303) Secure Key Exchange Mechanism for Internet (SKEMI) (41) security association (SA) (325) single sign-on (SSO) (294) superuser (290) ticket-granting server (TGS) (308) token (296) user (289) username (289)

virtual private network (VPN) (323)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. _______________ is an authentication model designed around the concept of using tickets for accessing objects.

2. _______________ is designed around the type of tasks people perform.

3. A formal manner of describing the necessary and sufficient portions of the IPsec protocol series to achieve a specific level of protection is a(n) _______________.

4. _______________ describes a system where every resource has access rules set for it all of the time.

5. _______________ is an authentication process where the user can enter their user ID (or username) and password and then be able to move from application to application or resource to resource without having to supply further authentication information.

6. In IPsec, a security association is defined by a specific combination of _______________ and _______________.

7. The protection of the data portion of a packet is _______________. 8. The protection of the header portion of a packet is

_______________.

9. _______________ is a key management and exchange protocol used with IPsec.

10. The process of comparing credentials to those established during the identification process is referred to as _______________.

Multiple-Choice Quiz 1. Authentication is typically based upon what?

A. Something a user possesses

B. Something a user knows

C. Something measured on a user, such as a fingerprint

D. All of the above

2. On a VPN, traffic is encrypted and decrypted at: A. Endpoints of the tunnel only

B. Users’ machines

C. Each device at each hop

D. The data link layer of access devices

3. A ticket-granting server is an important element in which of the following authentication models?

A. L2TP

B. RADIUS

C. PPP

D. Kerberos

4. What protocol is used for RADIUS? A. UDP

B. NetBIOS

C. TCP

D. Proprietary

5. Under which access control system is each piece of information and every system resource (files, devices, networks, and so on) labeled with its sensitivity level?

A. Discretionary access control

B. Resource access control

C. Mandatory access control

D. Media access control

6. IPsec provides which options as security services? A. ESP and AH

B. ESP and AP

C. EA and AP

D. EA and AH

7. Secure Shell uses which port to communicate? A. TCP port 80

B. UDP port 22

C. TCP port 22

D. TCP port 110

8. Elements of Kerberos include which of the following? A. Tickets, ticket-granting server, ticket-authorizing agent

B. Ticket-granting ticket, authentication server, ticket

C. Services server, Kerberos realm, ticket authenticators

D. Client-to-server ticket, authentication server ticket, ticket

9. To establish a PPTP connection across a firewall, you must do

which of the following?

A. Do nothing; PPTP does not need to cross firewalls by design.

B. Do nothing; PPTP traffic is invisible and tunnels past firewalls.

C. Open a UDP port of choice and assign it to PPTP.

D. Open TCP port 1723.

10. To establish an L2TP connection across a firewall, you must do which of the following?

A. Do nothing; L2TP does not cross firewalls by design.

B. Do nothing; L2TP tunnels past firewalls.

C. Open a UDP port of choice and assign it to L2TP.

D. Open UDP port 1701.

Essay Quiz 1. A co-worker with a strong Windows background is having difficulty

understanding UNIX file permissions. Describe UNIX file permissions for him. Compare UNIX file permissions to Windows file permissions.

2. How are authentication and authorization alike and how are they different. What is the relationship, if any, between the two?

3. What is a VPN and what technologies are used to create one?

Lab Projects

• Lab Project 11.1

Using two workstations and some routers, set up a simple VPN. Using Wireshark (a shareware network protocol analyzer, available at http://wireshark.com), observe traffic inside and outside the tunnel to demonstrate protection.

• Lab Project 11.2 Using freeSSHd and freeFTPd (both shareware programs, available at www.freesshd.com) and Wireshark, demonstrate the security features of SSH compared to Telnet and FTP.

chapter 12 Wireless Security and Mobile Devices

We must plan for freedom, and not only for security, if for no other reason than that only freedom can make security secure.

W

—KARL POPPER

In this chapter, you will learn how to

Describe the different wireless systems in use today

Detail WAP and its security implications

Identify 802.11’s security issues and possible solutions

Examine the elements needed for enterprise wireless deployment

Examine the security of mobile systems

ireless is increasingly the way people access the Internet. Because wireless access is considered a consumer benefit, many businesses have added wireless access points to lure customers into their shops.

With the rollout of fourth-generation (4G) high-speed cellular networks, people are also increasingly accessing the Internet from their mobile phones. The massive growth in popularity of nontraditional computers such as netbooks, e-readers, and tablets has also driven the popularity of wireless access. As wireless use increases, the security of the wireless protocols has

become a more important factor in the security of the entire network. As a security professional, you need to understand wireless network applications because of the risks inherent in broadcasting a network signal where anyone can intercept it. Sending unsecured information across public airwaves is tantamount to posting your company’s passwords by the front door of the building. This chapter opens with looks at several current wireless protocols and their security features. The chapter finishes with an examination of mobile systems and their security concerns.

Introduction to Wireless Networking Wireless networking is the transmission of packetized data by means of a physical topology that does not use direct physical links. This definition

can be narrowed to apply to networks that use radio waves to carry the signals over either public or private bands, instead of using standard network cabling. Some proprietary applications like long-distance microwave links use point-to-point technology with narrowband radios and highly directional antennas. However, this technology is not common enough to produce any significant research into its vulnerabilities, and anything that was developed would have limited usefulness. So this chapter focuses on point-to-multipoint systems, the two most common of which are the family of cellular protocols and IEEE 802.11. IEEE 802.11 is a family of protocols instead of a single specification; this is a summary table of the 802.11 family.

The IEEE 802.11 protocol has been standardized by the IEEE for wireless local area networks (LANs). Three versions are currently in production—802.11g, 802.11a, and 802.11n. The latest standard is 802.11ac, but it provides backward compatibility with 802.11g hardware. Cellular phone technology has moved rapidly to embrace data transmission and the Internet. The Wireless Application Protocol (WAP) was one of the pioneers of mobile data applications, but it has been overtaken by a variety of protocols pushing us to fourth-generation (4G) mobile networks.

Tech Tip

Wireless Systems There are several different wireless bands in common use today, the most common of which is the Wi-Fi series, referring to the 802.11 Wireless LAN standards certified by the Wi-Fi Alliance. Another set of bands is WiMAX, which refers to the set of 802.16 wireless network standards ratified by the WiMAX Forum. Lastly, there is ZigBee, a low-power, personal area networking technology described by the IEEE 802.15.4 series.

Bluetooth is a short-range wireless protocol typically used on small devices such as mobile phones. Early versions of these phones also had Bluetooth on and discoverable as a default, making the compromise of a nearby phone easy. Security research has focused on finding problems with these devices simply because the devices are so common. The security world ignored wireless for a long time, and then within the

space of a few months, it seemed like everyone was attempting to breach the security of wireless networks and transmissions. One reason wireless suddenly found itself to be such a target is that wireless networks are so abundant and so unsecured. The dramatic proliferation of these inexpensive products has made the security ramifications of the protocol astonishing. No matter what the system, wireless security is a very important topic as

more and more applications are designed to use wireless to send data. Wireless is particularly problematic from a security standpoint, because there is no control over the physical layer of the traffic. In most wired LANs, the administrators have physical control over the network and can control to some degree who can actually connect to the physical medium. This prevents large amounts of unauthorized traffic and makes snooping around and listening to the traffic difficult. Wireless does away with the physical limitations. If an attacker can get close enough to the signal’s source as it is being broadcast, he can at the very least listen to the access point and clients talking to capture all the packets for examination, as depicted in Figure 12.1.

• Figure 12.1 Wireless transmission extending beyond the facility’s walls

Attackers can also try to modify the traffic being sent or try to send their own traffic to disrupt the system. In this chapter, you will learn about the different types of attacks that wireless networks face.

Mobile Phones When cellular phones first hit the market, security wasn’t an issue—if you wanted to keep your phone safe, you’d simply keep it physically secure and not loan it to people you didn’t want making calls. Its only function was that of a telephone.

• Early cell phones just allowed you to make calls.

The advance of digital circuitry has added amazing power in smaller and smaller devices, causing security to be an issue as the software becomes more and more complicated. Today’s small and inexpensive products have made the wireless market grow by leaps and bounds, as traditional wireless devices such as cellular phones and pagers have been replaced by tablets and smartphones.

• Today’s phones allow you to carry computers in your pocket.

Today’s smartphones support multiple wireless data access methods,

including 802.11, Bluetooth, and cellular. These mobile phones and tablet devices have caused consumers to demand access to the Internet anytime and anywhere. This has generated a demand for additional data services. The Wireless Application Protocol (WAP) attempted to satisfy the needs for more data on mobile devices, but it is falling by the wayside as the mobile networks’ capabilities increase. The need for more and more bandwidth has pushed carriers to adopt a more IP-centric routing methodology with technologies such as High Speed Packet Access (HSPA) and Evolution Data Optimized (EVDO). Mobile phones have ruthlessly advanced with new technologies and services, causing phones and the carrier networks that support them to be described in generations —1G, 2G, 3G, and 4G. 1G refers to the original analog cellular standard, Advanced Mobile Phone System (AMPS). 2G refers to the digital network that superseded it. 3G is the system of mobile networks that followed, with many different implementations carrying data at up to 400 Kbps. 4G represents the current state of mobile phones with LTE being the primary method. 4G allows carriers to offer a wider array of services to the consumer, including broadband data service up to 14.4 Mbps and video calling. 4G is also a move to an entirely IP-based network for all services, running voice over IP (VoIP) on your mobile phone and speeds up to 1 Gbps. All of these “gee-whiz” features are nice, but how secure are your bits

and bytes going to be when they’re traveling across a mobile carrier’s network? All the protocols mentioned have their own security implementations—WAP applies its own Wireless Transport Layer Security (WTLS) to attempt to secure data transmissions, but WAP still has issues such as the “WAP gap” (as discussed next). 3G networks have attempted to push a large amount of security down the stack and rely on the encryption designed into the wireless protocol.

Tech Tip

Relationship of WAP and WTLS Wireless Application Protocol is a lightweight protocol designed for mobile devices. Wireless Transport Layer Security is a lightweight security protocol designed for WAP.

Wireless Application Protocol WAP was introduced to compensate for the relatively low amount of computing power on handheld devices as well as the generally poor network throughput of cellular networks. It uses the Wireless Transport Layer Security (WTLS) encryption scheme, which encrypts the plaintext data and then sends it over the airwaves as ciphertext. The originator and the recipient both have keys to decrypt the data and reproduce the plaintext. This method of ensuring confidentiality is very common, and if the encryption is well designed and implemented, it is difficult for unauthorized users to take captured ciphertext and reproduce the plaintext that created it. As described in Chapter 5, confidentiality is the ability to keep protected data a secret. WTLS uses a modified version of the Transport Layer Security (TLS) protocol, which is the replacement for Secure Sockets Layer (SSL). The WTLS protocol supports several popular bulk encryption algorithms, including Data Encryption Standard (DES), Triple DES (3DES), RC5, and International Data Encryption Algorithm (IDEA).

Cross Check Symmetric Encryption In Chapter 5 you learned about symmetric encryption, including DES, 3DES, RC5, and IDEA. In the context of wireless communication, what algorithm would protect your data the best? What are some possible problems with these algorithms?

WTLS implements integrity through the use of message authentication codes (MACs). A MAC algorithm generates a one-way hash of the

compressed WTLS data. WTLS supports the MD5 and SHA MAC algorithms. The MAC algorithm is also decided during the WTLS handshake. The TLS protocol that WTLS is based on is designed around Internet-based computers, machines that have relatively high processing power, large amounts of memory, and sufficient bandwidth available for Internet applications. Devices that WTLS must accommodate are limited in all these respects. Thus, WTLS has to be able to cope with small amounts of memory and limited processor capacity, as well as long round- trip times that TLS could not handle well. These requirements are the primary reasons that WTLS has security issues. As the protocol is designed around more capable servers than devices,

the WTLS specification can allow connections with little to no security. Clients with low memory or CPU capabilities cannot support encryption, and choosing null or weak encryption greatly reduces confidentiality. Authentication is also optional in the protocol, and omitting authentication reduces security by leaving the connection vulnerable to a man-in-the- middle–type attack. In addition to the general flaws in the protocol’s implementation, several known security vulnerabilities exist, including those to the chosen-plaintext attack, the PKCS #1 attack, and the alert message truncation attack. The chosen-plaintext attack works on the principle of a predictable

initialization vector (IV). By the nature of the transport medium that it is using, WAP, WTLS needs to support unreliable transport. This forces the IV to be based on data already known to the client, and WTLS uses a linear IV computation. Because the IV is based on the sequence number of the packet, and several packets are sent unencrypted, entropy is severely decreased. This lack of entropy in the encrypted data reduces confidentiality.

Tech Tip

Weakness in WAP Aggregation

WAP is a point-to-multipoint protocol, but it can face disruptions or attacks because it aggregates at well-known points: the cellular antenna towers.

Now consider the PKCS #1 attack. Public Key Cryptography Standards (PKCS), used in conjunction with RSA encryption, provide standards for formatting the padding used to generate a correctly formatted block size. When the client receives the block, it will reply to the sender as to the validity of the block. An attacker takes advantage of this by attempting to send multiple guesses at the padding to force a padding error. In vulnerable implementations, when RSA signatures and encryption are performed per PKCS #1, the RSA messages can be decrypted with approximately 220 chosen ciphertext queries. Alert messages in WTLS are sometimes sent in plaintext and are not authenticated. This fact could allow an attacker to overwrite an encrypted packet from the actual sender with a plaintext alert message, leading to possible disruption of the connection through, for instance, a truncation attack. Some concern over the so-called WAP gap involves confidentiality of

information where the two different networks meet, the WAP gateway, as shown in Figure 12.2.

• Figure 12.2 The WAP gap shows an unencrypted space between two enciphered connections.

WTLS acts as the security protocol for the WAP network, and TLS is the standard for the Internet, so the WAP gateway has to perform translation from one encryption standard to the other. This translation forces all messages to be seen by the WAP gateway in plaintext. This is a weak point in the network design, but from an attacker’s perspective, it’s a much more difficult target than the WTLS protocol itself. Threats to the WAP gateway can be minimized through careful infrastructure design, such as selecting a secure physical location and allowing only outbound traffic from the gateway. A risk of compromise still exists, however, and an attacker would find a WAP gateway an especially appealing target, as plaintext messages are processed through it from all wireless devices, not just a single user. The solution for this is to have end-to-end security layered over anything underlying, in effect creating a VPN from the endpoint to the mobile device, or to standardize on a full implementation

of TLS for end-to-end encryption and strong authentication. The limited nature of the devices hampers the ability of the security protocols to operate as intended, compromising any real security to be implemented on WAP networks.

3G Mobile Networks Our cell phones are one of the most visible indicators of advancing technology. Within recent memory, we were forced to switch from old analog phones to digital models. The networks have been upgraded to 3G, greatly enhancing speed and lowering latency. This has reduced the need for lightweight protocols to handle data transmission, and more standard protocols such as IP can be used. The increased power and memory of the handheld devices also reduce the need for lighter-weight encryption protocols. This has caused the protocols used for 3G mobile devices to build in their own encryption protocols. Security will rely on these lower- level protocols or standard application-level security protocols used in normal IP traffic. Several competing data transmission standards exist for 3G networks,

such as HSPA and EVDO. However, all the standards include transport layer encryption protocols to secure the voice traffic traveling across the wireless signal as well as the data sent by the device. The cryptographic standard proposed for 3G is known as KASUMI. This modified version of the MISTY1 algorithm uses 64-bit blocks and 128-bit keys. Multiple attacks have been launched against this cipher. While the attacks tend to be impractical, this shows that application layer security is needed for secure transmission of data on mobile devices. WAP and WTLS can be used over the lower-level protocols, but traditional TLS can also be used.

3G, 4G, LTE…What’s the Difference? In today’s mobile marketing campaigns, we hear of 3G, 4G, and LTE. What do these terms mean? 3G is the “old” network today, but it is still very capable for a variety of purposes. 4G phones are supposed to be even faster, but that’s not always the case. A lot depends on what you use the phone for. There are several technologies called “4G,” each with multiple implementations. This makes the term almost meaningless from a technical point of view. The

International Telecommunication Union (ITU), a standards body, issued requirements that a network needed to meet to be called “4G,” but those requirements were ignored by carriers. Now the move is to LTE, which stands for Long Term Evolution of the Universal Mobile Telecommunications System (UMTS). UMTS is the group of standards that defines 3G for GSM networks across the world, and now LTE. There are numerous technical implementations of LTE, but one of the key elements is the use of two different types of air interfaces (radio links), one for downlink (from tower to device) and one for uplink (from device to tower). This is one of the reasons LTE is much faster when uploading information from the phone to the Internet. LTE offers high speed (up to 30 Mbps) and low latency. But not all LTE is equal. Recent tests indicate as much as an order of magnitude difference in speeds between carriers. As LTE expands, newer versions, each with its own set of characteristics picked from the

overall “standard,” are deployed by carriers. While the LTE-A standard has been approved, no carriers currently meet the entire standard. Each carrier has picked the elements of the standard they feel meet their needs. Bottom line: 4G has become a marketing term, and the only guide one has is to use actual

survey results in the area of your service to determine the best solution for your use requirements.

4G Mobile Networks Just as the mobile network carriers were finishing the rollout of 3G services, 4G networks appeared on the horizon. The desire for anywhere, anytime Internet connectivity at speeds near that of a wired connection drives deployment of these next-generation services. 4G can support high- quality VoIP connections, video calls, and real-time video streaming. Just as 3G had some intermediaries that were considered 2.9G, LTE and WiMAX networks are sometimes referred to as 3.5G, 3.75G, or 3.9G. The carriers are marketing these new networks as 4G, although they do not adhere to the ITU standards for 4G speeds. True 4G would require a firm to meet all of the technical standards

issued by the ITU, including specifications that apply to the tower side of the system. Some of the 4G requirements are

Be based on an all-IP packet switched network

Offer high quality of service for next-generation multimedia support

Smooth handovers across heterogeneous networks

Peak data rates of up to approximately 100 Mbps for high mobility (mobile access)

Peak data rates of up to approximately 1 Gbps for low mobility such as nomadic/local wireless access

Dynamically share and use the network resources to support more simultaneous users per cell

Use scalable channel bandwidths of 5–20 MHz, optionally up to 40 MHz

Peak link spectral efficiency of 15-bps/Hz in the downlink, and 6.75- bps/Hz in the uplink

To achieve these and other technical elements requires specific tower- side equipment as well as handset specifications. Different carriers have chosen different sets of these to include in their offerings, each building upon their existing networks and existing technologies. Most 4G deployments are continuations of technologies already

deployed—just newer evolutions of standards. This is how LTE, LTE Advanced, WiMAX, and WiMAX 2 were born. LTE and WiMAX series come from separate roots, and are not interchangeable. Within the families, interoperability is possible and is dependent upon carrier implementation.

Bluetooth Bluetooth was originally developed by Ericsson and known as multi- communicator link; in 1998, Nokia, IBM, Intel, and Toshiba joined Ericsson and adopted the Bluetooth name. This consortium became known as the Bluetooth Special Interest Group (SIG). The SIG now has more than 24,000 members and drives the development of the technology and controls the specification to ensure interoperability.

• Bluetooth icon

Most people are familiar with Bluetooth as it is part of many mobile phones and headsets, such as those shown in Figure 12.3. This short-range, low-power wireless protocol transmits in the 2.4 GHz band, the same band used for 802.11. The concept for the short-range (approx. 32 feet) wireless protocol is to transmit data in personal area networks (PANs).

• Figure 12.3 Headsets and cell phones are two of the most popular types of Bluetooth-capable devices.

Bluetooth transmits and receives data from a variety of devices, the most common being mobile phones, laptops, printers, and audio devices. The mobile phone has driven a lot of Bluetooth growth and has even

spread Bluetooth into new cars as a mobile phone hands-free kit. Bluetooth has gone through a few releases. Version 1.1 was the first

commercially successful version, with version 1.2 released in 2007 and correcting some of the problems found in 1.1. Version 1.2 allows speeds up to 721 Kbps and improves resistance to interference. Version 1.2 is backward-compatible with version 1.1. With the rate of advancement and the life of most tech items, Bluetooth 1 series is basically extinct. Bluetooth 2.0 introduced enhanced data rate (EDR), which allows the transmission of up to 3.0 Mbps. Bluetooth 3.0 has the capability to use an 802.11 channel to achieve speeds up to 24 Mbps. The current version is the Bluetooth 4.0 standard with support for three modes: classic, high speed, and low energy. Bluetooth 4 introduces a new method to support collecting data from

devices that generate data at a very low rate. Some devices, such as medical devices, may only collect and transmit data at low rates. This feature, called Low Energy (LE), was designed to aggregate data from various sensors, like heart rate monitors, thermometers, and so forth, and carries the commercial name Bluetooth Smart.

Tech Tip

Bluetooth Security Bluetooth should always have discoverable mode turned off unless you’re deliberately pairing a device.

As Bluetooth became popular, people started trying to find holes in it. Bluetooth features easy configuration of devices to allow communication, with no need for network addresses or ports. Bluetooth uses pairing to establish a trust relationship between devices. To establish that trust, the devices advertise capabilities and require a passkey. To help maintain security, most devices require the passkey to be entered into both devices; this prevents a default passkey–type attack. The Bluetooth’s protocol

advertisement of services and pairing properties is where some of the security issues start.

Tech Tip

Bluetooth Data Rates Different versions of Bluetooth have differing maximum data transfer rates.

Bluetooth Attacks As a wireless method of communication, Bluetooth is open to connection and attack from outside the intended sender and receiver. Several different attack modes have been discovered that can be used against Bluetooth systems. Bluejacking is a term used for the sending of unauthorized messages to

another Bluetooth device. This involves setting a message as a phonebook contact:

Then the attacker sends the message to the possible recipient via Bluetooth. Originally, this involved sending text messages, but more recent phones can send images or audio as well. A popular variant of this is the transmission of “shock” images, featuring disturbing or crude photos. As Bluetooth is a short-range protocol, the attack and victim must be within roughly 10 yards of each other. The victim’s phone must also have Bluetooth enabled and must be in discoverable mode. On some early phones, this was the default configuration, and while it makes connecting external devices easier, it also allows attacks against the phone. If Bluetooth is turned off, or if the device is set to nondiscoverable,

bluejacking can be avoided. Bluesnarfing is similar to bluejacking in that it uses the same contact

transmission protocol. The difference is that instead of sending an unsolicited message to the victim’s phone, the attacker copies off the victim’s information, which can include e-mails, contact lists, calendar, and anything else that exists on that device. More recent phones with media capabilities can be snarfed for private photos and videos. Bluesnarfing used to require a laptop with a Bluetooth adapter, making it relatively easy to identify a possible attacker, but bluesnarfing applications are now available for mobile devices. Bloover, a combination of Bluetooth and Hoover, is one such application that runs as a Java applet. The majority of Bluetooth phones need to be discoverable for the bluesnarf attack to work, but it does not necessarily need to be paired. In theory, an attacker can also brute-force the device’s unique 48-bit name. A program called RedFang attempts to perform this brute-force attack by sending all possible names and seeing what gets a response. This approach was addressed in Bluetooth 1.2 with an anonymity mode. Bluebugging is a far more serious attack than either bluejacking or

bluesnarfing. In bluebugging, the attacker uses Bluetooth to establish a serial connection to the device. This allows access to the full AT command set—GSM phones use AT commands similar to Hayes-compatible modems. This connection allows full control over the phone, including the

placing of calls to any number without the phone owner’s knowledge. Fortunately, this attack requires pairing of the devices to complete, and phones initially vulnerable to the attack have updated firmware to correct the problem. To accomplish the attack now, the phone owner would need to surrender her phone and allow an attacker to physically establish the connection. Bluetooth DOS is the use of Bluetooth technology to perform a denial-

of-service attack against another device. In this attack, an attacker repeatedly requests pairing with the victim device. This type of attack does not divulge information or permit access, but is a nuisance. And, more

importantly, if done repeatedly it can drain a device’s battery, or prevent other operations from occurring on the victim’s device. As with all Bluetooth attacks, because of the short range involved, all one has to do is leave the area and the attack would cease. Bluetooth technology is likely to grow due to the popularity of mobile

phones. Software and protocol updates have helped to improve the security of the protocol. Almost all phones now keep Bluetooth turned off by default, and they allow you to make the phone discoverable for only a limited amount of time. User education about security risks is also a large factor in avoiding security breaches.

Near Field Communication Near field communication (NFC) is a set of wireless technologies that enables smartphones and other devices to establish radio communication over a short proximity, typically a distance of 10 cm (3.9 in) or less. This technology did not see much use until recently when it started being employed to move data between cell phones and in mobile payment systems. NFC is likely to become a high use technology in the years to come as multiple uses exist for the technology, and the next generation of smartphones is surely to see this as a standard function.

IEEE 802.11 Series The 802.11b protocol is an IEEE standard ratified in 1999. The standard launched a range of products (such as wireless routers, an example of which is shown in Figure 12.4) that would open the way to a whole new genre of possibilities for attackers and a new series of headaches for security administrators everywhere. 802.11 was a new standard for sending packetized data traffic over radio waves in the unlicensed 2.4 GHz band.

• Figure 12.4 A common wireless router

This group of IEEE standards is also called Wi-Fi, which is a certification owned by an industry group, the Wi-Fi Alliance. A device marked as Wi-Fi Certified adheres to the standards of the alliance. As the products matured and became easy to use and affordable, security experts began to deconstruct the limited security that had been built into the

standard. The 802.11b standard was the first to market, 802.11a followed, and

802.11g products currently are the most common ones being sold. These chipsets have also commonly been combined into devices that support a/b/g standards. 802.11n is the latest standard. This table shows the standards with their frequency ranges.

802.11a is the wireless networking standard that supports traffic on the 5 GHz band, allowing faster speeds over shorter ranges. Features of 802.11b and 802.11a were later joined to create 802.11g, an updated standard that allows the faster speeds of the 5 GHz specification on the 2.4 GHz band. Security problems were discovered in the implementations of these early wireless standards, principally involving the Wired Equivalent

Privacy (WEP) protocol. These problems included an attacker’s ability to break the cryptography and monitor other users’ traffic. The security problems in WEP were a top concern until the adoption of 802.11i- compliant products enhanced the security with Wi-Fi Protected Access (WPA), discussed later in the chapter. 802.11ac is the latest standard; it focuses on achieving much higher speeds for wireless networks. Direct- sequence spread spectrum (DSSS) is a modulation type that spreads the traffic sent over the entire bandwidth. It does this by injecting a noise-like signal into the information stream and transmitting the normally narrowband information over the wider band available. The primary reason that spread-spectrum technology is used in 802.11 protocols is to avoid interference on the public 2.4 GHz and 5 GHz bands. Orthogonal frequency division multiplexing (OFDM) multiplexes, or separates, the data to be transmitted into smaller chunks and then transmits the chunks on several subchannels. This use of subchannels is what the “frequency division” portion of the name refers to. Both of these techniques, multiplexing and frequency division, are used to avoid interference. Orthogonal refers to the manner in which the subchannels are assigned, principally to avoid crosstalk, or interference with your own channels.

802.11: Individual Standards The 802.11b protocol provides for multiple-rate Ethernet over 2.4 GHz spread-spectrum wireless. It provides transfer rates of 1 Mbps, 2 Mbps, 5.5 Mbps, and 11 Mbps and uses DSSS. The most common layout is a point- to-multipoint environment, with the available bandwidth being shared by all users. Typical range is roughly 100 yards indoors and 300 yards outdoors, line of sight. While the wireless transmissions of 802.11 can penetrate some walls and other objects, the best range is offered when both the access point and network client devices have an unobstructed view of each other. 802.11a uses a higher band and has higher bandwidth. It operates in the

5 GHz spectrum using OFDM. Supporting rates of up to 54 Mbps, it is the

faster brother of 802.11b; however, the higher frequency used by 802.11a shortens the usable range of the devices and makes it incompatible with 802.11b. The chipsets tend to be more expensive for 802.11a, which has slowed adoption of the standard. The 802.11g standard uses portions of both of the other standards: it

uses the 2.4 GHz band for greater range but uses the OFDM transmission method to achieve the faster 54 Mbps data rates. As it uses the 2.4 GHz band, this standard interoperates with the older 802.11b standard. This allows an 802.11g access point (AP) to give access to both “G” and “B” clients. The 802.11n version improves on the older standards by greatly

increasing speed. It has a functional data rate of up to 600 Mbps, gained through the use of wider bands and multiple-input multiple-output (MIMO) processing. MIMO uses multiple antennas and can bond separate channels together to increase data throughput. 802.11ac is the latest in the 5 GHz band, with functional data rates up to

a theoretical 6+ Gbps using multiple antennas. The 802.11ac standard was ratified in 2014, and chipsets have been available since late 2011. Designed for multimedia streaming and other high-bandwidth operations, the individual channels are twice the width of 802.11n channels, and as many as eight antennas can be deployed in a Mu-MIMO form. 802.11 proposals don’t stop with “ac” though. There are several ideas

that extend the 802.11 standard for new and interesting applications. For example, 802.11s is a proposed standard for wireless mesh networks where all nodes on the network are equal instead of using an access point and a client. 802.11p is another example; it defines an application where mobile vehicles can communicate with other vehicles or roadside stations for safety information or toll collection. All these protocols operate in bands that are “unlicensed” by the FCC.

This means that people operating this equipment do not have to be certified by the FCC, but it also means that the devices could possibly share the band with other devices, such as cordless phones, closed-circuit TV (CCTV) wireless transceivers, and other similar equipment. This other

equipment can cause interference with the 802.11 equipment, possibly causing speed degradation.

The 2.4 GHz band is commonly used by many household devices that are constantly on, such as cordless phones. It is also the frequency used by microwave ovens to heat food. So if you are having intermittent interference on your Wi-Fi LAN, check to see if the microwave is on.

The 802.11 protocol designers expected some security concerns and attempted to build provisions into the 802.11 protocol that would ensure adequate security. The 802.11 standard includes attempts at rudimentary authentication and confidentiality controls. Authentication is handled in its most basic form by the 802.11 AP, forcing the clients to perform a handshake when attempting to “associate” to the AP.

SSIDs can be set to anything by the person setting up an access point. So, while “FBI Surveillance Van #14” may seem humorous, what about SSIDs with the name of the airport you are in, Starbucks, or the hotel you are in? Can you trust them? Since anyone can use any name, the answer is no. So, if you need a secure connection, you should use some form of secure channel such as a VPN for communication security. For even more security, you can carry your own access point and create a wireless channel that you control.

Association is the process required before the AP will allow the client to talk across the AP to the network. Association occurs only if the client has all the correct parameters needed in the handshake, among them the service set identifier (SSID). This SSID setting should limit access only to the authorized users of the wireless network. The SSID is a phrase- based mechanism that helps ensure that you are connecting to the correct AP. This SSID phrase is transmitted in all the access point’s beacon frames. The beacon frame is an 802.11 management frame for the network and contains several different fields, such as the timestamp and beacon interval, but most importantly the SSID. This allows attackers to

scan for the beacon frame and retrieve the SSID. The designers of the 802.11 standard also attempted to maintain

confidentiality by introducing Wired Equivalent Privacy (WEP), which uses the RC4 stream cipher to encrypt the data as it is transmitted through the air. WEP has been shown to have an implementation problem that can be exploited to break security. To understand all the 802.11 security problems, you must first look at

some of the reasons it became such a prominent technology. Wireless networks came along in 2000 and became very popular. For the first time, it was possible to have almost full-speed network connections without having to be tied down to an Ethernet cable. The technology quickly took off, allowing prices to drop into the consumer range. Once the market shifted to focus on customers who were not necessarily technologists, the products also became very easy to install and operate. Default settings were designed to get the novice users up and running without having to alter anything substantial, and products were described as being able to just plug in and work. These developments further enlarged the market for the low-cost, easy-to-use wireless access points. Then attackers realized that instead of attacking machines over the Internet, they could drive around and seek out these APs. Typically, access to actual Ethernet segments is protected by physical

security measures. This structure allows security administrators to plan for only internal threats to the network and gives them a clear idea of the types and number of machines connected to it. Wireless networking takes the keys to the kingdom and tosses them out the window and into the parking lot. A typical wireless installation broadcasts the network right through the physical controls that are in place. An attacker can drive up and have the same access as if he plugged into an Ethernet jack inside the building—in fact, better access, because 802.11 is a shared medium, allowing sniffers to view all packets being sent to or from the AP and all clients. These APs are also typically behind any security measures the companies have in place, such as firewalls and intrusion detection systems (IDSs). This kind of access into the internal network has caused a large stir among computer

security professionals and eventually the media. War-driving, war-flying, war-walking, war-chalking—all of these terms have been used in security article after security article to describe attacks on wireless networks.

Cross Check Intrusion Detection Systems Chapter 13 has a lot more information about intrusion detection systems, whereas this chapter references methods of getting past the IDSs. When you learn more about the different IDSs, how would you design an IDS that can catch wireless attackers?

Attacking 802.11 Wireless is a popular target for several reasons: the access gained from wireless, the lack of default security, and the wide proliferation of devices. However, other reasons also make it attackable. The first of these is anonymity: An attacker can probe your building for wireless access from the street. Then he can log packets to and from the AP without giving any indication that an attempted intrusion is taking place. The attacker will announce his presence only if he attempts to associate to the AP. Even then, an attempted association is recorded only by the MAC address of the wireless card associating to it, and most APs do not have alerting functionality to indicate when users associate to it. This fact gives administrators a very limited view of who is gaining access to the network, if they are even paying attention at all. It gives attackers the ability to seek out and compromise wireless networks with relative impunity. The second reason is the low cost of the equipment needed. A single

wireless access card costing less than $100 can give access to any unsecured AP within driving range. Finally, attacking a wireless network is relatively easy compared to attacking other target hosts. Windows-based tools for locating and sniffing wireless-based networks have turned anyone who can download files from the Internet and has a wireless card into a potential attacker.

Locating wireless networks was originally termed war-driving, an adaptation of the term war-dialing. War-dialing comes from the 1983 movie WarGames; it is the process of dialing a list of phone numbers looking for modem-connected computers. War-drivers drive around with a wireless locater program recording the number of networks found and their locations. This term has evolved along with war-flying and war-walking, which mean exactly what you expect. War-chalking started with people using chalk on sidewalks to mark some of the wireless networks they found.

Anonymity also works in another way; once an attacker finds an unsecured AP with wireless access, they can use an essentially untraceable IP address to attempt attacks on other Internet hosts.

The most common tools for an attacker to use are reception-based programs that listen to the beacon frames output by other wireless devices, and programs that promiscuously capture all traffic. The most widely used of these programs is called NetStumbler, created by Marius Milner and shown in Figure 12.5. This program listens for the beacon frames of APs that are within range of the card attached to the NetStumbler computer. When it receives the frames, it logs all available information about the AP for later analysis. Since it listens only to beacon frames, NetStumbler displays only networks that have the SSID broadcast turned on. If the computer has a GPS unit attached to it, the program also logs the AP’s coordinates. This information can be used to return to the AP or to plot maps of APs in a city.

• Figure 12.5 NetStumbler on a Windows PC

NetStumbler is a Windows-based application, but programs for other operating systems such as OS X, BSD, Linux, and others work on the same principle.

Exam Tip: Because wireless antennas can transmit outside a facility, the proper tuning and placement of these antennas can be crucial for security. Adjusting radiated power through these power-level controls will assist in keeping wireless signals from being broadcast outside areas

under physical access control.

Once an attacker has located a network, and assuming that he cannot directly connect and start active scanning and penetration of the network, he will use the best attack tool there is: a network sniffer. The network sniffer, when combined with a wireless network card it can support, is a powerful attack tool, as the shared medium of a wireless network exposes all packets to interception and logging. Popular wireless sniffers are Wireshark (formerly Ethereal) and Kismet. Regular sniffers used on wired Ethernet have also been updated to include support for wireless. Sniffers are also important because they allow you to retrieve the MAC addresses of the nodes of the network. APs can be configured to allow access only to prespecified MAC addresses, and an attacker spoofing the MAC can bypass this feature. There are specialized sniffer tools designed with a single objective: to

crack Wired Equivalent Privacy (WEP) keys. As described earlier, WEP is an encryption protocol that 802.11 uses to attempt to ensure confidentiality of wireless communications. Unfortunately, it has turned out to have several problems. WEP’s weaknesses are specifically targeted for attack by the specialized sniffer programs. They work by exploiting weak initialization vectors in the encryption algorithm. To exploit this weakness, an attacker needs a certain number of ciphertext packets; once he has captured enough packets, however, the program can very quickly decipher the encryption key being used. WEPCrack was the first available program to use this flaw to crack WEP keys; however, WEPCrack depends on a dump of actual network packets from another sniffer program. AirSnort is a standalone program that captures its own packets; once it has captured enough ciphertext, it provides the WEP key of the network.

Tech Tip

IV Attack Because of the small length of the initialization vector (IV) in WEP, the protection is subject

to attack over time by examining packets and determining when the IV + RC4 key repeats, enabling the defeat of the protection.

Local users of the network are susceptible to having their entire traffic decoded and analyzed. A proper site survey is an important step in securing a wireless network to avoid sending critical data beyond company walls. Recurring site surveys are important because wireless technology is cheap and typically comes unsecured in its default configuration. If anyone attaches a wireless AP to your network, you want to know about it immediately.

Tech Tip

Another Meaning of Rogue Access Point A “rogue access point” can also refer to an attacker’s access point, set up as a man in the middle to capture login information from unsuspecting users.

If unauthorized wireless is set up, it is known as a rogue access point. Rogue access points can be set up by well-meaning employees or hidden by an attacker with physical access. An attacker might set up a rogue access point if they have a limited amount of physical access to an organization, perhaps by sneaking into the building briefly. The attacker can then set up an AP on the network and, by placing it behind the external firewall or network IDS (NIDS) type of security measures, can attach to the wireless at a later date at their leisure. This approach reduces the risk of getting caught by physical security staff, and if the AP is found, it does not point directly back to any kind of traceable address. Another type of 802.11 attack is known as the evil twin attack. This is

the use of an access point owned by an attacker that usually has been enhanced with higher-power and higher-gain antennas to look like a better connection to the users and computers attaching to it. By getting users to connect through the evil access point, attackers can more easily analyze

traffic and perform man-in-the-middle−type attacks. For simple denial of service, an attacker could use interference to jam the wireless signal, not allowing any computer to connect to the access point successfully.

Cross Check Identifying Rogue Access Points In Chapter 8 you learned about how physical security can impact information security, and how several different devices can act as a wireless bridge and be a rogue access point. Can you think of some physical security policies that can help reduce the risk of rogue access points? What about some information security policies?

802.11 networks have two features used primarily for security: one is designed solely for authentication, and the other is designed for authentication and confidentiality. Part of the authentication function, introduced earlier, is known as the service set identifier (SSID). This unique 32-octet identifier is attached to the header of the packet. The SSID is broadcast by default as a network name, but broadcasting of this beacon frame can be disabled. Users can authenticate to a network regardless of whether the SSID is broadcast or not, but they do need to know the SSID to connect. Many APs also use a default SSID; for Cisco APs, this default is

tsunami, which may indicate an AP that has not been configured for any security. Renaming the SSID and disabling SSID broadcast are both good ideas; however, because the SSID is part of every frame, these measures should not be considered adequate to secure the network. As the SSID is, hopefully, a unique identifier, only people who know the identifier will be able to complete association to the AP. While the SSID is a good idea in theory, it is sent in plaintext in the packets, so in practice SSID offers little security significance—any sniffer can determine the SSID. This weakness is magnified by most APs’ default settings to transmit

beacon frames. The beacon frame’s purpose is to announce the wireless network’s presence and capabilities so that WLAN cards can attempt to

associate to it. This can be disabled in software for many APs, especially the more sophisticated ones. From a security perspective, the beacon frame is damaging because it contains the SSID, and this beacon frame is transmitted at a set interval (ten times per second by default). Since a default AP without any other traffic is sending out its SSID in plaintext ten times a second, you can see why the SSID does not provide true authentication. Scanning programs such as NetStumbler work by capturing the beacon frames and thereby the SSIDs of all APs.

Exam Tip: MAC filtering can be employed on WAPs but can be bypassed by attackers observing allowed MAC addresses and spoofing the allowed MAC address for the wireless card.

Most APs also have the ability to lock access in only to known MAC addresses, providing a limited authentication capability. Given sniffers’ capacity to grab all active MAC addresses on the network, this capability is not very effective. An attacker simply configures his wireless cards to a known good MAC address. WEP encrypts the data traveling across the network with an RC4 stream

cipher, attempting to ensure confidentiality. This synchronous method of encryption ensures some method of authentication. The system depends on the client and the AP having a shared secret key, ensuring that only authorized people with the proper key have access to the wireless network. WEP supports two key lengths, 40 and 104 bits, though these are more typically referred to as 64 and 128 bits, because 24 bits of the overall key length are used for the initialization vector (IV). In 802.11a and 802.11g, manufacturers have extended this to 152-bit WEP keys, again with 24 bits being used for the IV.

Tech Tip

WEP Isn’t Equivalent WEP should not be trusted alone to provide confidentiality. If WEP is the only protocol supported by your AP, place it outside the corporate firewall and VPN to add more protection.

The IV is the primary reason for the weaknesses in WEP. The IV is sent in the plaintext part of the message, and because the total keyspace is approximately 16 million keys, the same key will be reused. Once the key has been repeated, an attacker has two ciphertexts encrypted with the same key stream. This allows the attacker to examine the ciphertext and retrieve the key. This attack can be improved by examining only packets that have weak IVs, reducing the number of packets needed to crack the key. Using only weak IV packets, the number of required captured packets is reduced to around four or five million, which can take only a few hours to capture on a fairly busy AP. For a point of reference, this means that equipment with an advertised WEP key of 128 bits can be cracked in less than a day, whereas to crack a normal 128-bit key would take roughly 2,000,000,000,000,000,000 years on a computer able to attempt one trillion keys a second. As mentioned, AirSnort is a modified sniffing program that takes advantage of this weakness to retrieve the WEP keys. The biggest weakness of WEP is that the IV problem exists regardless

of key length, because the IV always remains at 24 bits. After the limited security functions of a wireless network are broken, the

network behaves exactly like a regular Ethernet network and is subject to the exact same vulnerabilities. The host machines that are on or attached to the wireless network are as vulnerable as if they and the attacker were physically connected. Being on the network opens up all machines to vulnerability scanners, Trojan horse programs, virus and worm programs, and traffic interception via sniffer programs. Any unpatched vulnerability on any machine accessible from the wireless segment is now open to compromise.

Current Security Methods

WEP was designed to provide some measure of confidentiality on an 802.11 network similar to what is found on a wired network, but that has not been the case. Accordingly, the Wi-Fi Alliance developed Wi-Fi Protected Access (WPA) to improve upon WEP. The 802.11i standard is the IEEE standard for security in wireless networks, also known as Wi-Fi Protected Access 2 (WPA2). It uses 802.1X to provide authentication. WPA2 can use Advanced Encryption Standard (AES) as the encryption protocol. The 802.11i standard specifies the use of the Temporal Key Integrity Protocol (TKIP) and uses AES with the Counter Mode with CBC-MAC Protocol (in full, the Counter Mode with Cipher Block Chaining–Message Authentication Codes Protocol, or simply CCMP). These two protocols have different functions, but they both serve to enhance security. TKIP works by using a shared secret combined with the card’s MAC

address to generate a new key, which is mixed with the IV to make per- packet keys that encrypt a single packet using the same RC4 cipher used by traditional WEP. This overcomes the WEP key weakness, as a key is used on only one packet. The other advantage to this method is that it can be retrofitted to current hardware with only a software change, unlike AES and 802.1X. CCMP is actually the mode in which the AES cipher is used to provide message integrity. Unlike TKIP, CCMP requires new hardware to perform the AES encryption. The advances of 802.11i have corrected the weaknesses of WEP.

WPA The first standard to be used in the market to replace WEP was Wi-Fi Protected Access (WPA). This standard uses the flawed WEP algorithm with the Temporal Key Integrity Protocol (TKIP). While WEP uses a 40-bit or 104-bit encryption key that must be

manually entered on wireless access points and devices and does not change, TKIP employs a per-packet key, generating a new 128-bit key for each packet. This can generally be accomplished with only a firmware update, enabling a simple solution to the types of attacks that compromise

WEP.

TKIP Temporal Key Integrity Protocol (TKIP) was created as a stopgap security measure to replace the WEP protocol without requiring the replacement of legacy hardware. The breaking of WEP had left Wi-Fi networks without viable link-layer security, and a solution was required for already deployed hardware. TKIP works by mixing a secret root key with the IV before the RC4 encryption. WPA/TKIP uses the same underlying mechanism as WEP, and consequently is vulnerable to a number of similar attacks. TKIP is no longer considered secure and has been deprecated with the release of WPA2.

WPA2 IEEE 802.11i is the standard for security in wireless networks and is also known as Wi-Fi Protected Access 2 (WPA2). It uses 802.1x to provide authentication and uses the Advanced Encryption Standard (AES) as the encryption protocol. WPA2 uses the AES block cipher, a significant improvement over WEP’s and WPA’s use of the RC4 stream cipher. The 802.11i standard specifies the use of the Counter Mode with CBC-MAC Protocol (in full, the Counter Mode with Cipher Block Chaining–Message Authentication Codes Protocol, or simply CCMP).

WPS Wi-Fi Protected Setup (WPS) is a network security standard that was created to provide users with an easy method of configuring wireless networks. Designed for home networks and small business networks, this standard involves the use of an eight-digit PIN to configure wireless devices. WPS consists of a series of Extensible Authentication Protocol (EAP) messages and has been shown to be susceptible to a brute-force attack. A successful attack can reveal the PIN and subsequently the WPA/WPA2 passphrase and allow unauthorized parties to gain access to

the network. Currently, the only effective mitigation is to disable WPS.

Setting Up WPA2 If WPS is not safe for use, how does one set up WPA2? To set up WPA2, you need to have several parameters. Figure 12.6 shows the screens for a WPA2 setup in Windows 7.

• Figure 12.6 WPA2 setup options in Windows 7

The first element is to choose a security framework. When configuring an adapter to connect to an existing network, you need to match the choice of the network. When setting up your own network, you can choose whichever option you prefer. There are many selections, but for security purposes, you should choose WPA2-Personal or WPA2-Enterprise. Both of these require the choice of an encryption type, either TKIP or AES. TKIP has been deprecated, so choose AES. The last element is the choice of the network security key—the secret that is shared by all users. WPA2- Enterprise, which is designed to be used with an 802.1x authentication server that distributes different keys to each user, is typically used in business environments.

EAP Extensible Authentication Protocol (EAP) is defined in RFC 2284 (obsoleted by 3748). EAP-TLS relies on Transport Layer Security (TLS), an attempt to standardize the SSL structure to pass credentials. EAP-TTLS (the acronym stands for EAP–Tunneled TLS protocol) is a variant of the EAP-TLS protocol. EAP-TTLS works much the same way as EAP-TLS, with the server authenticating to the client with a certificate, but the protocol tunnels the client side of the authentication, allowing the use of legacy authentication protocols such as Password Authentication Protocol (PAP), Challenge-Handshake Authentication Protocol (CHAP), MS- CHAP, or MS-CHAP-V2.

LEAP Cisco designed a proprietary EAP known as Lightweight Extensible Authentication Protocol (LEAP); however, this is being phased out for newer protocols such as PEAP or EAP-TLS. Susceptible to offline password guessing, and with tools available that actively break LEAP security, this protocol has been deprecated in favor of stronger methods of

EAP.

PEAP PEAP, or Protected EAP, was developed to protect the EAP communication by encapsulating it with TLS. This is an open standard developed jointly by Cisco, Microsoft, and RSA. EAP was designed assuming a secure communication channel. PEAP provides that protection as part of the protocol via a TLS tunnel. PEAP is widely supported by vendors for use over wireless networks.

Implementing 802.1X The IEEE 802.1X protocol can support a wide variety of authentication methods and also fits well into existing authentication systems such as RADIUS and LDAP. This allows 802.1X to interoperate well with other systems such as VPNs and dial-up RAS. Unlike other authentication methods, such as the Point-to-Point Protocol over Ethernet (PPPoE), 802.1X does not use encapsulation, so the network overhead is much lower. Unfortunately, the protocol is just a framework for providing implementation, so no specifics guarantee strong authentication or key management. Implementations of the protocol vary from vendor to vendor in method of implementation and strength of security, especially when it comes to the difficult test of wireless security. Three common methods are used to implement 802.1X: EAP-TLS,

EAP-TTLS, and EAP-MD5. EAP-TLS relies on TLS, an attempt to standardize the SSL structure to pass credentials. The standard, developed by Microsoft, uses X.509 certificates and offers dynamic WEP key generation. This means that the organization must have the ability to support the public key infrastructure (PKI) in the form of X.509 digital certificates. Also, per-user, per-session dynamically generated WEP keys help prevent anyone from cracking the WEP keys in use, as each user individually has her own WEP key. Even if a user were logged onto the AP and transmitted enough traffic to allow cracking of the WEP key, access would be gained only to that user’s traffic. No other user’s data

would be compromised, and the attacker could not use the WEP key to connect to the AP. This standard authenticates the client to the AP, but it also authenticates the AP to the client, helping to avoid man-in-the-middle attacks. The main problem with the EAP-TLS protocol is that it is designed to work only with Microsoft’s Active Directory and Certificate Services; it will not take certificates from other certificate issuers. Thus a mixed environment would have implementation problems. As discussed earlier, EAP-TTLS works much the same way as EAP-

TLS, with the server authenticating to the client with a certificate, but the protocol tunnels the client side of the authentication, allowing the use of legacy authentication protocols such as Password Authentication Protocol (PAP), Challenge-Handshake Authentication Protocol (CHAP), MS- CHAP, or MS-CHAP-V2. This makes the protocol more versatile while still supporting the enhanced security features such as dynamic WEP key assignment. EAP-MD5, while it does improve the authentication of the client to the

AP, does little else to improve the security of your AP. The protocol works by using the MD5 encryption protocol to hash a user’s username and password. This protocol, unfortunately, provides no way for the AP to authenticate with the client, and it does not provide for dynamic WEP key assignment. In the wireless environment, without strong two-way authentication, it is very easy for an attacker to perform a man-in-the- middle attack. Normally, these types of attacks are difficult to perform, requiring a traffic redirect of some kind, but wireless changes all those rules. By setting up a rogue AP, an attacker can attempt to get clients to connect to it as if it were authorized and then simply authenticate to the real AP, a simple way to have access to the network and the client’s credentials. The problem of not dynamically generating WEP keys is that it simply opens up the network to the same lack of confidentiality to which a normal AP is vulnerable. An attacker has to wait only for enough traffic to crack the WEP key, and he can then observe all traffic passing through the network. Because the security of wireless LANs has been so problematic, many

users have simply switched to a layered security approach—that is, they have moved their APs to untrustworthy portions of the network and have forced all clients to authenticate through the firewall to a third-party VPN system. The additional security comes at a price of putting more load on the firewall and VPN infrastructure and possibly adding cumbersome software to the users’ devices. While wireless can be set up in a very secure manner in this fashion, it can also be set up poorly. Some systems lack strong authentication of both endpoints, leading to possibilities of a man-in-the-middle attack. Also, even though the data is tunneled through, IP addresses are still sent in the clear, giving an attacker information about what and where your VPN endpoint is. Another phenomenon of wireless is borne out of its wide availability

and low price. All the security measures of the wired and wireless network can be defeated by the rogue AP. This is the third possible type of rogue access point discussed in this chapter; they all share the same name as they all represent a security breach. However, since they are implemented with different motives and accordingly pose slightly different threats, we discuss them all separately. In this case, a well-intentioned employee who is trying to make the work environment more convenient purchases an AP at a local retailer and installs it. When installed, it works fine, but it typically will have no security installed. Since the IT department doesn’t know about it, it is an uncontrolled entry point into the network. No matter what kind of rogue AP we are dealing with, the rogue AP

must be detected and controlled. The most common way to control rogue APs is some form of wireless scanning to ensure only legitimate wireless is in place at an organization. While complete wireless IDSs will detect APs, this can also be done with a laptop and free software.

Try This! Scanning for Rogue Wireless Once you have completed Lab Project 12.1 and have NetStumbler or Kismet installed on the computer, take it to several locations around your workplace or school and attempt to scan for

wireless access points that should not be there.

CCMP As previously mentioned in the discussion of WPA2, CCMP stands for Counter Mode with Cipher Block Chaining–Message Authentication Codes Protocol (or Counter Mode with CBC-MAC Protocol). CCMP is a data encapsulation encryption mechanism designed for wireless use. CCMP is actually the mode in which the AES cipher is used to provide message integrity. Unlike WPA, CCMP requires new hardware to perform the AES encryption.

MAC Filtering MAC filtering is the selective admission of packets based on a list of approved Media Access Control (MAC) addresses. Employed on switches, this method is used to provide a means of machine authentication. In wired networks, this enjoys the protection afforded by the wires, making interception of signals to determine their MAC addresses difficult. In wireless networks, this same mechanism suffers from the fact that an attacker can see the MAC addresses of all traffic to and from the access point, and then can spoof the MAC addresses that are permitted to communicate via the access point.

Exam Tip: MAC filtering can be employed on wireless access points, but can be bypassed by attackers observing allowed MAC addresses and spoofing the allowed MAC address for the wireless card.

Wireless Systems Configuration Wireless systems are more than just protocols. Putting up a functional

wireless system in a house is as easy as plugging in a wireless access point and connecting. But in an enterprise, where multiple access points will be needed, the configuration takes significantly more work. Site surveys are needed to determine proper access point and antenna placement, as well as channels and power levels.

Antenna Types The standard access point is equipped with an omnidirectional antenna. Omnidirectional antennas operate in all directions, making the relative orientation between devices less important. Omnidirectional antennas cover the greatest area per antenna. The weakness occurs in corners and hard-to-reach areas, as well as boundaries of a facility where directional antennas are needed to complete coverage. Figure 12.7 shows a sampling of common Wi-Fi antennas: (a) is a common home wireless router, (b) is a commercial indoor wireless access point, and (c) is an outdoor directional antenna. These can be visible as shown, or hidden above ceiling tiles.

• Figure 12.7 Wireless access point antennas

Wireless networking problems caused by weak signal strength can sometimes be solved by installing upgraded Wi-Fi radio antennas on the access points. On business networks, the complexity of multiple access points typically requires a comprehensive site survey to map the Wi-Fi

signal strength in and around office buildings. Additional wireless access points can then be strategically placed where needed to resolve dead spots in coverage. For small businesses and homes, where a single access point may be all that is needed, an antenna upgrade may be a simpler and more cost-effective option to fix Wi-Fi signal problems. Two common forms of upgraded antennas are the Yagi antenna and the

panel antenna. An example of a Yagi antenna is shown in Figure 12.7(c). Both Yagi and panel antennas are directional in nature, spreading the RF energy in a more limited field, increasing effective range in one direction while limiting it in others. Panel antennas can provide solid room performance while preventing signal bleed behind the antennas. This works well on the edge of a site, limiting the stray emissions that could be captured offsite. Yagi antennas act more like a rifle, funneling the energy along a beam. This allows much longer communication distances using standard power. This also enables eavesdroppers to capture signals from much greater distances because of the gain provided by the antenna itself.

Antenna Placement Wi-Fi is by nature a radio-based method of communication, and as such uses antennas to transmit and receive the signals. The actual design and placement of the antennas can have a significant effect on the usability of the radio frequency (RF) medium for carrying the traffic. Antennas come in a variety of types, each with its own transmission pattern and gain factor. High-gain antennas can deal with weaker signals, but also have more-limited coverage. Wide-coverage, omnidirectional antennas can cover wider areas, but at lower levels of gain. The objective of antenna placement is to maximize the coverage over a physical area and reduce low-gain areas. This can be very complex in buildings with walls, electrical interference, and other sources of interference and frequently requires a site survey to determine proper placement.

Exam Tip: Because wireless antennas can transmit outside a facility, tuning and placement of antennas can be crucial for security. Adjusting radiated power through the power level controls will assist in keeping wireless signals from being broadcast outside areas under physical access control.

MIMO MIMO is a set of multiple-input and multiple-output antenna technologies where the available antennas are spread over a multitude of independent access points each having one or multiple antennas. This can enhance the usable bandwidth and data transmission capacity between the access point and user. There are a wide variety of MIMO methods, and this technology, once considered cutting edge or advanced, is becoming mainstream.

Power Level Controls Wi-Fi power levels can be controlled by the hardware for a variety of reasons. The lower the power used, the less the opportunity for interference. But if the power levels are too low, then signal strength limits range. Access points can have the power level set either manually or via programmatic control. For most users, power level controls are not very useful, and leaving the unit in default mode is the best option. In complex enterprise setups, with site surveys and planned overlapping zones, this aspect of signal control can be used to increase capacity and control on the network.

Site Surveys When developing a coverage map for a complex building site, you need to take into account a wide variety of factors, particularly walls, interfering sources, and floor plans. A site survey involves several steps: mapping the

floor plan, testing for RF interference, testing for RF coverage, and analysis of material via software. The software can suggest placement of access points. After deploying the APs, the site is surveyed again, mapping the results versus the predicted, watching signal strength and signal-to- noise ratios. Figure 12.8 illustrates what a site survey looks like. The different shades indicate signal strength, showing where reception is strong and where it is weak. Site surveys can be used to ensure availability of wireless, especially when it’s critical for users to have connections.

• Figure 12.8 Example site survey

Exam Tip: Wireless networks are dependent upon radio signals to function. It is important to

understand that antenna type, placement, and site surveys are used to ensure proper coverage of a site, including areas blocked by walls, interfering signals, and echoes.

Captive Portals Captive portal refers to a specific technique of using an HTTP client to handle authentication on a wireless network. Frequently employed in public hotspots, a captive portal opens a web browser to an authentication page. This occurs before the user is granted admission to the network. The access point uses this simple mechanism by intercepting all packets and returning the web page for login. The actual web server that serves up the authentication page can be in a walled-off section of the network, blocking access to the Internet until the user successfully authenticates.

Securing Public Wi-Fi Public Wi-Fi is a common perk that some firms provide for their customers and visitors. When providing a Wi-Fi hotspot, even free open- to-the-public Wi-Fi, security should still be a concern. One of the issues associated with wireless transmissions is that they are subject to interception by anyone within range of the hotspot. This makes it possible for others to intercept and read traffic of anyone using the hotspot, unless encryption is used. For this reason, it has become common practice to use wireless security, even when the intent is to open the channel for everyone. Having a default password, even one that everyone knows, will make it so that people cannot observe other traffic. There is an entire open wireless movement, designed around a sharing

concept that promotes sharing of the Internet to all. For information, check out https://openwireless.org.

Mobile Devices This section will review a large number of topics specific to mobile

devices. You’ll likely find that the security principles you’ve already learned apply and just need to be adapted to mobile technologies. This is one of the fastest-changing areas of computer security because mobile technology is likely the fastest-changing technology.

Although the data transmissions between many mobile devices are secured via carrier methods (GSM) and device methods (RIM Blackberry), voice transmissions have been intercepted and later used to embarrass the parties. Third-party voice encryption methods exist for smartphones, but are considered expensive and difficult to deploy by most people. They also suffer from the problem that both ends of a conversation need the device to have a secured communication. As more and more businesses find value in secured voice communications, this solution may become mainstream in the future.

Many mobile devices have significant storage capacity, allowing them to transfer files and data. Data must be protected, devices must be properly configured, and good user habits must be encouraged. This makes mobile devices no different from any other mobile media source, capable of carrying and delivering viruses, worms, and other forms of malware. They are also capable of removing data from within a network, in the case of an insider attack. Mobile devices are also commonly Bluetooth enabled, making various wireless attacks against the device a risk. One reason to attack the mobile device is to use it to relay the attack onto the internal network when the device is synced up. Bluetooth attacks are covered in Chapter 12.

Mobile Device Security Security principles similar to those applicable to laptop computers must be followed when using mobile devices such as smartphones and tablet computing devices. Data must be protected, devices must be properly configured, and good user habits must be encouraged. This chapter will review a large number of topics specific to mobile devices. You’ll likely find that the security principles you’ve already learned apply and just need

to be adapted to mobile technologies. This is one of the fastest-changing areas of computer security because mobile technology is likely the fastest- changing technology.

Full Device Encryption Just as laptop computers should be protected with whole disk encryption to protect the laptop in case of loss or theft, you may need to consider encryption for mobile devices used by your company’s employees. Mobile devices are much more likely to be lost or stolen, so you should consider encrypting data on your devices. More and more, mobile devices are used when accessing and storing business-critical data or other sensitive information. Protecting the information on mobile devices is becoming a business imperative. This is an emerging technology, so you’ll need to complete some rigorous market analysis to determine what commercial product meets your needs.

Remote Wiping Today’s mobile devices are almost innumerable and are very susceptible to loss and theft. Further, it is unlikely that a lost or stolen device will be recovered, thus making even encrypted data stored on a device more vulnerable to decryption. If the thief can have your device for a long time, he can take all the time he wants to try to decrypt your data. Therefore, many companies prefer to just remotely wipe a lost or stolen device. Remote wiping a mobile device typically removes data stored on the device and resets the device to factory settings. There is a dilemma in the use of BYOD (bring your own device) devices that store both personal and enterprise data. Wiping the device usually removes all data, both personal and enterprise. Therefore, if corporate policy requires wiping a lost device that may mean the device’s user loses personal photos and data. The software controls for separate data containers, one for business and one for personal, are one of the reasons for enterprises to adopt mobile device management (MDM) solutions.

Lockout A user likely will discover in a relatively short time that they’ve lost their device, so a quick way to protect their device is to remotely lock the device as soon as they recognize it has been lost or stolen. Several products are available on the market today to help enterprises manage their devices. Remote lockout is usually the first step taken in securing a mobile device.

Screen-locks Most corporate policies regarding mobile devices require the use of the mobile device’s screen-locking capability. This usually consists of entering a passcode or PIN to unlock the device. It is highly recommended that screen locks be enforced for all mobile devices. Your policy regarding the quality of the passcode should be consistent with your corporate password policy. However, many companies merely enforce the use of screen-locking. Thus, users tend to use convenient or easy-to-remember passcodes. Some devices allow complex passcodes. As shown in Figure 12.9, the device screen on the left supports only a simple iOS passcode, limited to four numbers, while the device screen on the right supports a passcode of indeterminate length and can contain alphanumeric characters.

• Figure 12.9 iOS lock screens

Some more advanced forms of screen-locks work in conjunction with device wiping. If the passcode is entered incorrectly a specified number of times, the device is automatically wiped. This is one of the security features of BlackBerry that has traditionally made it of interest to security- conscious users. Apple has made this an option on newer iOS devices. Apple also allows remote locking of a device from the user’s iCloud account.

Tech Tip

Mobile Device Security Mobile devices require basic security mechanisms of screen-locks, lockouts, device wiping, and encryption to protect sensitive information contained on them.

GPS Most mobile devices are now capable of using the Global Positioning System (GPS) for tracking device location. Many apps rely heavily on GPS location, such as device-locating services, mapping apps, traffic monitoring apps, and apps that locate nearby businesses such as gas stations and restaurants. Such technology can be exploited to track movement location of the mobile device. This tracking can be used to assist in the recovery of lost devices.

Storage Segmentation On mobile devices, it can be very difficult to keep personal data separate from corporate data. Some companies have developed capabilities to create separate virtual containers to keep personal data separate from corporate data and applications. For devices that are used to handle highly

sensitive corporate data, this form of protection is highly recommended.

Asset Control Because each user can have multiple devices connecting to the corporate network, it is important to implement a viable asset tracking and inventory control mechanism. For security and liability reasons, the company needs to know what devices are connecting to its systems and what access has been granted. Just as in IT systems, maintaining a list of approved devices is a critical control.

Mobile Device Management Mobile device management (MDM) is one of the hottest topics in device security today. MDM began as a marketing term for a collective set of commonly employed protection elements associated with mobile devices. When viewed as a comprehensive set of security options for mobile devices, every corporation should have and enforce an MDM policy. The policy should require

Device locking with a strong password

Encryption of data on the device

Device locking automatically after a certain period of inactivity

The capability to remotely lock the device if it is lost or stolen

The capability to wipe the device automatically after a certain number of failed login attempts

The capability to remotely wipe the device if it is lost or stolen

Password policies should extend to mobile devices, including lockout and, if possible, the automatic wiping of data. Corporate policy for data encryption on mobile devices should be consistent with the policy for data encryption on laptop computers. In other words, if you don’t require encryption of portable computers, then should you require it for mobile

devices? There is not a uniform answer to this question; mobile devices are much more mobile in practice than laptops, and more prone to loss. This is ultimately a risk question that management must address: What is the risk and what are the costs of the options employed? This also raises a bigger question: Which devices should have encryption as a basic security protection mechanism? Is it by device type, or by user based on what data would be exposed to risk? Fortunately, MDM solutions exist to make the choices manageable.

Exam Tip: Mobile device management (MDM) is a marketing term for a collective set of commonly employed protection elements associated with mobile devices.

Device Access Control The principles of access control for mobile devices need to be managed just like access control from wired or wireless desktops and laptops. This will become more critical as storage in the cloud and Software as a Service (SaaS) become more prevalent. Emerging tablet/mobile device sharing intends to provide the user with a seamless data access experience across many devices. Data access capabilities will continue to evolve to meet this need. Rigorous data access principles need to be applied, and they become even more important with the inclusion of mobile devices as fully functional computing devices. When reviewing possible solutions, it is important to consider seeking proof of security and procedures rather than relying on marketing brochures.

Removable Storage Because removable devices can move data outside of the corporate- controlled environment, their security needs must be addressed. Removable devices can bring unprotected or corrupted data into the corporate environment. All removable devices should be scanned by

antivirus software upon connection to the corporate environment. Corporate policies should address the copying of data to removable devices. Many mobile devices can be connected via USB to a system and used to store data—and in some cases vast quantities of data. This capability can be used to avoid some implementations of data loss prevention mechanisms.

Disabling Unused Features As with all computing devices, features that are not used or that present a security risk should be disabled. Bluetooth access is particularly problematic. It is best to make Bluetooth connections undiscoverable. But, users will need to enable it to pair with a new headset or car connection, for example. Requiring Bluetooth connections to be undiscoverable is very hard to enforce but should be encouraged as a best practice. Users should receive training as to the risks of Bluetooth—not so they avoid Bluetooth, but so they understand when they should turn it off. Having a mobile device with access to sensitive information carries with it a level of responsibility. Helping users understand this and act accordingly can go a long way toward securing mobile devices.

BYOD Concerns Permitting employees to “bring your own device” (BYOD) has many advantages in business, and not just from the perspective of device cost. Users tend to prefer having a single device rather than carrying multiple devices. Users have less of a learning curve on devices they already have an interest in learning.

Data Ownership BYOD blurs the lines of data ownership because it blurs the lines of device management. If a company owns a smartphone issued to an employee, the company can repossess the phone upon employee

termination. This practice may protect company data by keeping the company-issued devices in the hands of employees only. However, a company cannot rely on a simple factory reset before reissuing a device, because factory resetting may not remove all the data on the device. If a device is reissued, it is possible that some of the previous owner’s personal information, such as private contacts, still remains on the device. On the other hand, if the employee’s device is a personal device that has been used for business purposes, upon termination of the employee, it is likely that some company data remains on the phone despite the company’s best efforts to remove its data from the device. If that device is resold or recycled, the company’s data may remain on the device and be passed on to the subsequent owner. Keeping business data in separate, MDM- managed containers is one method of dealing with this issue.

Tech Tip

BYOD Concerns There is a dilemma in the use of BYOD devices that store both personal and enterprise data. Wiping the device usually removes all data, both personal and enterprise. Therefore, if corporate policy requires wiping a lost device, that policy may mean the device’s user loses personal photos and data. The software controls for separate data containers, one for business and one for personal, have been proposed but are not a mainstream option yet.

Storage Segmentation On mobile devices, it can be very difficult to keep personal data separate from corporate data. Some companies have developed capabilities to create separate virtual containers to keep personal data separate from corporate data and applications. For devices that are used to handle highly sensitive corporate data, this form of protection is highly recommended.

Support Ownership Support costs for mobile devices are an important consideration for

corporations. Each device has its own implementation of various functions. While those functions typically are implemented against a specification, software implementations may not fully or properly implement the specification. This may result in increased support calls to your help desk or support organization. It is very difficult for a corporate help desk to be knowledgeable on all aspects of all possible devices that access a corporate network. For example, your support organization must be able to troubleshoot iPhones, Android devices, tablets, and so forth. These devices are updated frequently, new devices are released, and new capabilities are added on a regular basis. Your support organization will need viable knowledge base articles and job aids in order to provide sufficient support for the wide variety of ever-changing devices.

Patch Management Just as your corporate policy should enforce the prompt update of desktop and laptop computers to help eliminate security vulnerabilities on those platforms, it should also require mobile devices to be kept current with respect to patches. Having the latest applications, operating system, and so on is an important best defense against viruses, malware, and other threats. It is important to recognize that “jailbreaking” or “rooting” your device may remove the manufacturer’s security mechanisms and protection against malware and other threats. These devices may also no longer be able to update their applications or OS against known issues. Jailbreaking or rooting is also a method used to bypass security measures associated with the device manufacturer control, and in some locations, this can be illegal. Mobile devices that are jailbroken or rooted should not be trusted on your enterprise network or allowed to access sensitive data.

Antivirus Management Just like desktop and laptop computers, smartphones, tablets, and other mobile devices need protection against viruses and malware. It is important that corporate policy and personal usage keep operating systems and applications current. Antivirus and malware protection should be

employed as widely as possible and kept up-to-date against current threats.

Forensics Mobile device forensics is a rapidly evolving and fast-changing field. Because devices are evolving so quickly and changing so fast, it is difficult to stay current in this field. Solid forensics principles should always be followed. Devices should be properly handled by using RF-shielded bags or containers. Because of the rapid changes in this area, it’s best to engage the help of trained forensic specialists to ensure data isn’t contaminated and the device state and memory are unaltered. If forensics are needed on a device that has both personal and business data, then policies need to be in place to cover the appropriate privacy protections on the personal side of the device.

Privacy When an employee uses his personal device to perform his work for the company, he may have strong expectations that privacy will be protected by the company. The company policy needs to consider this and address it explicitly. On company-owned devices, it’s quite acceptable for the company to reserve the right to access and wipe any company data on the device. The company can thus state that the user can have no expectation of privacy when using a company device. But when the device is a personal device, the user may feel stronger ownership. Expectations of privacy and data access on personal devices should be included in your company policy.

On-board Camera/Video Many mobile devices include on-board cameras, and the photos/videos they take can divulge information. This information can be associated with anything the camera can image—whiteboards, documents, even the location of the device when the photo/video was taken via geo-tagging. Another challenge presented by mobile devices is the possibility that they

will be used for illegal purposes. This can create liability for the company if it is a company-owned device. Despite all the potential legal concerns, possibly the greatest concern of mobile device users is that their personal photos will be lost during a device wipe originated by the company.

On-boarding/Off-boarding Most companies and individuals find it relatively easy to connect mobile devices to the corporate network. Often there are not controls around connecting a device other than having a Microsoft Exchange account. When new employees join a company, the on-boarding processes need to include provisions for mobile device responsibilities. It is easy for new employees to bypass security measures if they are not part of the business process of on-boarding. Employee termination needs to be modified to include termination of

accounts on mobile devices. It’s not uncommon to find terminated employees with accounts or even company devices still connecting to the corporate network months after being terminated. E-mail accounts should be removed promptly as part of the employee termination policy and process. Mobile devices supplied by the company should be collected upon termination. BYOD equipment should have its access to corporate resources terminated as part of the off-boarding process. Regular audits for old or unterminated accounts should be performed to ensure prompt deletion of accounts for terminated employees.

Adherence to Corporate Policies Your corporate policies regarding BYOD devices should be consistent with your existing computer security policies. Your training programs should include instruction on mobile device security. Disciplinary actions should be consistent. Your monitoring programs should be enhanced to include monitoring and control of mobile devices.

User Acceptance

BYOD inherently creates a conflict between personal and corporate interests. An employee who uses her own device to conduct corporate business inherently feels strong ownership over the device and may resent corporate demands to control corporate information downloaded to the device. On the other hand, the corporation expects that corporate data be properly controlled and protected and thus desires to impose remote wiping or lockout requirements in order to protect corporate data. An individual who loses her personal photos from a special event will likely harbor ill feelings toward the corporation if it wipes her device, including those irreplaceable photos. Your corporate BYOD policy needs to be well defined, approved by the corporate legal department, and clearly communicated to all employees through training.

Architecture/Infrastructure Considerations Mobile devices consume connections to your corporate IT infrastructure. It is not unusual now for a single individual to be connected to the corporate infrastructure with one or more smartphones, tablets, and laptop or desktop computers. Some infrastructure implementations in the past have not been efficient in their design, sometimes consuming multiple connections for a single device. This can reduce the number of available connections for other end users. It is recommended that load testing be performed to ensure that your design or existing infrastructure can support the potentially large number of connections from multiple devices. Multiple connections can also create security issues when the system

tracks user accounts against multiple connections. Users will need to be aware of this, so that they don’t inadvertently create incident response situations or find themselves locked out by their own actions. This can be a tricky issue requiring a bit more intelligent design than the traditional philosophy of one userid equals one current connection.

Legal Concerns It should be apparent from the various topics discussed in this chapter that there are many security challenges presented by mobile devices used for

corporate business. Because the technology is rapidly changing, it’s best to make sure you have solid legal review of policies. There are both legal and public relation concerns when it comes to mobile devices. Employees who use both company-owned and personal devices have responsibilities when company data is involved. Policies and procedures should be reviewed on a regular basis to stay current with technology. Another challenge presented by mobile devices is the possibility that

they will be used for illegal purposes. This can create liability for the company if it is a company-owned device.

Acceptable Use Policy Similar to your acceptable use policies for laptops and desktops, your mobile device policies should address acceptable use of mobile or BYOD devices. Authorized usage of corporate devices for personal purposes should be addressed. Disciplinary actions for violation of mobile device policies should be defined. BYOD offers both the company and the user advantages; ramifications should be specifically spelled out, along with the specific user responsibilities.

Exam Tip: Mobile devices offer many usability advantages across the enterprise, and they can be managed securely with the help of security-conscious users. Security policies can go a long way toward assisting users in understanding their responsibilities associated with mobile devices and sensitive data.

Location Services Mobile devices by their specific nature can move, and hence location of the device can have significant ramifications with respect to its use. Mobile devices can connect to multiple public Wi-Fi locations, and they can provide users with navigation and other location context-sensitive information, such as a local sale. To enable this functionality, location

services are a set of functions to enable, yet control, the location information possessed by the device.

Geo-Tagging Geo-tagging is the posting of location information into a data stream signifying where the device was when the stream was created. As many mobile devices include on-board cameras, and the photos/videos they take can divulge information, geo-tagging can make location part of any picture or video. This information can be associated with anything the camera can image—whiteboards, documents, even the location of the device when the photo/video was taken via geo-tagging. Posting photos with geo-tags embedded in them has its use, but it can

also unexpectedly publish information that users may not want to share. For example, if you use your smartphone to take a photo of your car in the driveway and then post the photo on the Internet in an attempt to sell your car, if geo-tagging was enabled on the smartphone, the location of where the photo was taken is embedded as metadata in the digital photo. Such a posting could inadvertently expose where your home is located. Some social media applications strip out the metadata on a photo before posting, but then they post where you posted it from in the posting itself. There has been much public discussion on this topic, and geo-tagging can be disabled on most mobile devices. It is recommended that it be disabled unless you have a specific reason for having the location information embedded in the photo.

Mobile Application Security Devices are not the only concern in the mobile world. Applications that run on the devices also represent security threats to the information that is stored on and processed by the device. Applications are the software elements that can be used to violate security, even when the user is not aware. Many games and utilities offer value to the user, but at the same time they scrape information stores on the device for information.

Application Control Most mobile device vendors provide some kind of app store for finding and purchasing apps for their mobile devices. The vendors do a reasonable job of making sure that offered apps are approved and don’t create an overt security risk. Yet many apps request access to various information stores on the mobile device as part of their business model. Understanding what access is requested and approved upon installation of apps is an important security precaution. Your company may have to restrict the types of apps that can be downloaded and used on mobile devices. If you need very strong protection, your company can be very proactive and provide an enterprise app store where only company-approved apps are available, with a corresponding policy that apps cannot be obtained from any other source.

Key and Credential Management The MDM marketplace is maturing quickly. Key and credential management services are being integrated into most MDM services to ensure that existing strong policies and procedures can be extended to mobile platforms securely. These services include protection of keys for digital signatures and S/MIME encryption and decryption. Keys and credentials are among the highest-value items that can be found on mobile devices, so ensuring protection for them is a key element in mobile device security. The keys and credentials stored on the device can be used by multiple applications. Providing protection of these keys while still maintaining usability of them is an essential element of modern mobile application security.

Authentication When mobile devices are used to access business networks, authentication becomes an issue. There are several levels of authentication that can be an issue. Is the device allowed to access the network? Is the user of the device a network user? If so, how do you authenticate the user? Mobile devices

have some advantages in that they can store certificates, which by their very nature are more secure than passwords. This moves the authentication problem to the endpoint, where it relies on passcodes, screen-locks, and other mobile device protections. These can be relatively weak unless structured together, including wiping after a limited number of failures. The risk in mobile authentication is that strong credentials stored in the device are protected by the less rigorous passcode and the end user. End users can share their mobile devices, and by proxy unwittingly share their strong corporate authentication codes.

Application Whitelisting As discussed in the “Application Control” section earlier in the chapter, controlling what applications a device can access may be an important element of your company’s mobile device policy. Application whitelisting and blacklisting enables you to control and block applications available on the mobile device. This is usually administered through some type of MDM capability. Application whitelisting can improve security by preventing unapproved applications from being installed and run on the device.

Encryption Just as the device should be encrypted, thereby protecting all information on the device, applications should be encrypted as well. Just employing encryption for the data store is not sufficient. If the device is fully encrypted, then all apps would have to have access to the data, in essence bypassing the encryption from an app point of view. Apps with sensitive information should control access via their own set of protections. The only way to segregate data within the device is for apps to manage their own data stores through app-specific encryption. This will allow sensitive data to be protected from rogue applications that would leak data if uniform access was allowed.

Transitive Trust/Authentication Security across multiple domains/platforms is provided through trust relationships. When trust relationships between domains or platforms exist, authentication for each domain trusts the authentication for all other trusted domains. Thus when an application is authenticated, its authentication is accepted by all other domains/platforms that trust the authenticating domain or platform. Trust relationships can be very complex in mobile devices, and often security aspects aren’t properly implemented. Mobile devices tend to be used across numerous systems, including business, personal, public, and private. This greatly expands the risk profile and opportunity for transitive trust–based attacks. As with all other applications, mobile applications should be carefully reviewed to ensure that trust relationships are secure.

Chapter 12 Review

Chapter Summary After reading this chapter and completing the exercises, you should understand the following about wireless security and mobile devices.

Describe the different wireless systems in use today

Wireless Application Protocol (WAP) is used on small, handheld devices like cell phones for out-of-the-office connectivity.

802.11 is the IEEE standard for wireless local area networks. The standard includes several different specifications of 802.11 networks, such as 802.11b, 802.11a, 802.11g, and 802.11n.

Detail WAP and its security implications

WAP is the data protocol used by many cellular phones to deliver e- mail and lightweight web services.

Designers created WTLS as a method to ensure privacy of data being broadcast over WAP.

WTLS has a number of inherent security problems, such as weak encryption necessitated by the low computing power of the devices and the network transition that must occur at the cellular provider’s network, or the WAP gap.

Identify 802.11’s security issues and possible solutions

802.11 does not allow physical control of the transport mechanism.

Transmission of all network data wirelessly transmits frames to all wireless machines, not just a single client, similar to Ethernet hub devices.

Poor authentication is caused by the SSID being broadcast to anyone listening.

Flawed implementation of the RC4 encryption algorithm makes even encrypted traffic subject to interception and decryption.

Examine the elements needed for enterprise wireless deployment

Wireless coverage can be a function of antenna type, placement, and power levels.

Captive portals can be used to control access to wireless systems.

Examine the security of mobile systems

Mobile devices have specific security concerns and specific controls to assist in securing them.

BYOD has its own concerns and policies and procedures to manage mobile devices in the enterprise.

Mobile applications require security, and the issues associated with mobile, apps, and security need to be addressed.

Key Terms 2.4 GHz band (344) 5 GHz band (348) beacon frames (349) bluebugging (346) bluejacking (345) bluesnarfing (346) Bluetooth DOS (346) captive portal (362) confidentiality (340) direct-sequence spread spectrum (DSSS) (348) evil twin (352) geo-tagging (370) IEEE 802.1X (357) IEEE 802.11 (337) initialization vector (IV) (340) jailbreaking (367) MAC filtering (359) MIMO (361) mobile device management (MDM) (365) near field communication (NFC) (347) orthogonal frequency division multiplexing (OFDM) (348) RC4 stream cipher (350) remote wiping (363) rogue access point (352) screen locking (363) service set identifier (SSID) (349)

site survey (361) Temporal Key Integrity Protocol (TKIP) (355) WAP gap (341) Wi-Fi Protected Access 2 (WPA2) (355) WiMax (337) Wired Equivalent Privacy (WEP) (350) Wireless Application Protocol (WAP) (339) Wireless Transport Layer Security (WTLS) (340) ZigBee (337)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. An AP uses _______________ to advertise its existence to potential wireless clients.

2. The _______________ is the part of the RC4 cipher that has a weak implementation in WEP.

3. Two common mobile device security measures are _______________ and _______________.

4. WAP uses the _______________ protocol to attempt to ensure confidentiality of data.

5. The 32-character identifier attached to the header of a packet used for authentication to an 802.11 access point is the _______________.

6. _______________ is a feature that can disclose a user’s position when sharing photos.

7. 802.11i updates the flawed security deployed in _______________. 8. The standard for wireless local area networks is called

_______________.

9. The type of application used to control security across multiple mobile devices in an enterprise is called _______________.

10. 802.11a uses frequencies in the _______________.

Multiple-Choice Quiz 1. Bluebugging can give an attacker what?

A. All of your contacts

B. The ability to send “shock” photos

C. Total control over a mobile phone

D. A virus

2. How does 802.11n improve network speed? A. Wider bandwidth

B. Higher frequency

C. Multiple-input multiple-output (MIMO)

D. Both A and C

3. WTLS ensures integrity through what device? A. Public key encryption

B. Message authentication codes

C. Source IP

D. Digital signatures

4. WEP has used an implementation of which of the following encryption algorithms?

A. SHA

B. ElGamal

C. RC4

D. Triple-DES

5. What element does not belong in a mobile device security policy in an enterprise employing BYOD?

A. Separation of personal and business-related information

B. Remote wiping

C. Passwords and screen-locking

D. Mobile device carrier selection

6. What is bluejacking? A. Stealing a person’s mobile phone

B. Sending an unsolicited message via Bluetooth

C. Breaking a WEP key

D. Leaving your Bluetooth in discoverable mode

7. While the SSID provides some measure of authentication, why is it not very effective?

A. It is dictated by the manufacturer of the access point.

B. It is encrypted.

C. It is broadcast in every beacon frame.

D. SSID is not an authentication function.

8. The 802.1X protocol is a protocol for Ethernet: A. Authentication

B. Speed

C. Wireless

D. Cabling

9. What is the best way to avoid problems with Bluetooth? A. Keep personal info off your phone

B. Keep Bluetooth discoverability off

C. Buy a new phone often

D. Encryption

10. Why is attacking wireless networks so popular? A. There are more wireless networks than wired.

B. They all run Windows.

C. It’s easy.

D. It’s more difficult and more prestigious than other network attacks.

Essay Quiz 1. Produce a report on why sensitive information should not be sent

over the Wireless Application Protocol.

2. When you want to start scanning for rogue wireless networks, your supervisor asks you to write a memo detailing the threats of rogue wireless access points. What information would you include in the memo?

3. Write a security policy for company-owned cell phones that use the Bluetooth protocol.

4. Write a memo recommending upgrading your organization’s old

802.11b infrastructure to an 802.11i-compliant network, and detail the security enhancements.

Lab Projects

• Lab Project 12.1 Set up NetStumbler or Kismet on a computer, and then use it to find wireless access points. You will need the following:

A laptop with Windows or Linux installed

A compatible wireless 802.11 network adapter Then do the following: 1. Download NetStumbler from www.netstumbler.com or Kismet from

www.kismetwireless.net. 2. For NetStumbler, run the Windows Installer. For Kismet, untar the source file and then

execute, in order, ./configure, make, and make install.

3. Start the program and make sure that it sees your wireless adapter. 4. Take the laptop on your normal commute (or drive around your neighborhood) with

NetStumbler/Kismet running.

5. Log any access points you detect.

• Lab Project 12.2 Attempt to scan the area for Bluetooth devices. You will need a cell phone with Bluetooth installed or a computer with a Bluetooth adapter. Then do the following:

1. If you’re using a PC, download BlueScanner from SourceForge at http://sourceforge.net/projects/bluescanner/.

2. Take your phone or computer to a place with many people, such as a café.

3. Start the program and make sure that it sees your Bluetooth adapter. 4. Attempt to scan for vulnerable Bluetooth devices.

5. If you’re using your phone, tell it to scan for Bluetooth devices. Any devices that you find are running in “discoverable” mode and are potentially exploitable.

chapter 13 Intrusion Detection Systems and Network

Security

One person’s “paranoia” is another person’s “engineering redundancy.”

—MARCUS J. RANUM

A

In this chapter, you will learn how to

Apply the appropriate network tools to facilitate network security

Determine the appropriate use of tools to facilitate network security

Apply host-based security applications

n intrusion detection system (IDS) is a security system that detects inappropriate or malicious activity on a computer or network. Most organizations use their own approaches to network security, choosing

the layers that make sense for them after they weigh risks, potentials for loss, costs, and manpower requirements. The foundation for a layered network security approach usually starts

with a well-secured system, regardless of the system’s function (whether it’s a user PC or a corporate e-mail server). A well-secured system uses up-to-date application and operating system patches, requires well-chosen passwords, runs the minimum number of services necessary, and restricts access to available services. On top of that foundation, you can add layers of protective measures such as antivirus products, firewalls, sniffers, and IDSs. Some of the more complicated and interesting types of network/data

security devices are IDSs, which are to the network world what burglar alarms are to the physical world. The main purpose of an IDS is to identify suspicious or malicious activity, note activity that deviates from normal behavior, catalog and classify the activity, and, if possible, respond to the activity.

History of Intrusion Detection Systems Like much of the network technology we see today, IDSs grew from a need to solve specific problems. Like the Internet itself, the IDS concept came from U.S. Department of Defense–sponsored research. In the early

1970s, the U.S. government and military became increasingly aware of the need to protect the electronic networks that were becoming critical to daily operations.

Early History of IDS In 1972, James Anderson published a paper for the U.S. Air Force outlining the growing number of computer security problems and the immediate need to secure Air Force systems (James P. Anderson, “Computer Security Technology Planning Study Volume 2,” October 1972, http://seclab.cs.ucdavis.edu/projects/history/papers/ande72.pdf). Anderson continued his research and in 1980 published a follow-up paper outlining methods to improve security auditing and surveillance methods (“Computer Security Threat Monitoring and Surveillance,” April 15, 1980, http://csrc.nist.gov/publications/history/ande80.pdf). In this paper, Anderson pioneered the concept of using system audit files to detect unauthorized access and misuse. He also suggested the use of automated detection systems, which paved the way for misuse detection on mainframe systems in use at the time. While Anderson’s work got the efforts started, the concept of a real-time, rule-based IDS

didn’t really exist until Dorothy Denning and Peter Neumann developed the first real-time IDS model, called “The Intrusion Detection Expert System (IDES),” from their research between 1984 and 1986. In 1987, Denning published “An Intrusion-Detection Model,” a paper that laid out the model on which most modern IDSs are based (and which appears in IEEE Transactions on Software Engineering, Vol. SE-13, No. 2 [February 1987]: 222—232).

The U.S. government continued to fund research that led to projects such as Discovery, Haystack, Multics Intrusion Detection and Alerting System (MIDAS), and Network Audit Director and Intrusion Reporter (NADIR). Finally, in 1989, Haystack Labs released Stalker, the first commercial IDS. Stalker was host-based and worked by comparing audit data to known patterns of suspicious activity. While the military and government embraced the concept, the commercial world was very slow to adopt IDS products, and it was several years before other commercial products began to emerge. In the early to mid-1990s, as computer systems continued to grow,

companies started to realize the importance of IDSs; however, the solutions available were host-based and required a great deal of time and money to manage and operate effectively. Focus began to shift away from host-based systems, and network-based IDSs began to emerge. In 1995, WheelGroup was formed in San Antonio, Texas, to develop the first

commercial network-based IDS product, called NetRanger. NetRanger was designed to monitor network links and the traffic moving across the links to identify misuse as well as suspicious and malicious activity. NetRanger’s release was quickly followed by Internet Security Systems’ RealSecure in 1996. Several other players followed suit and released their own IDS products, but it wasn’t until the networking giant Cisco Systems acquired WheelGroup in February 1998 that IDSs were recognized as a vital part of any network security infrastructure. Figure 13.1 offers a timeline for these developments.

• Figure 13.1 History of the Internet and IDS

IDS Overview As mentioned, an IDS is somewhat like a burglar alarm. It watches the activity going on around it and tries to identify undesirable activity. IDSs are typically divided into two main categories, depending on how they monitor activity:

Exam Tip: Know the differences between host-based and network-based IDSs. A host-based IDS runs on a specific system (server or workstation) and looks at all the activity on that host. A network-based IDS sniffs traffic from the network and sees only activity that occurs on the network.

Host-based IDS (HIDS) Examines activity on an individual system, such as a mail server, web server, or individual PC. It is concerned only with an individual system and usually has no visibility into the activity on the network or systems around it.

Network-based IDS (NIDS) Examines activity on the network itself. It has visibility only into the traffic crossing the network link it is monitoring and typically has no idea of what is happening on individual systems.

Whether it is network- or host-based, an IDS typically consists of several specialized components working together, as illustrated in Figure 13.2. These components are often logical and software-based rather than physical and will vary slightly from vendor to vendor and product to product. Typically, an IDS has the following logical components:

• Figure 13.2 Logical depiction of IDS components

Traffic collector (or sensor) Collects activity/events for the IDS to examine. On a HIDS, this could be log files, audit logs, or traffic coming to or leaving a specific system. On a NIDS, this is typically a mechanism for copying traffic off the network link—basically functioning as a sniffer. This component is often referred to as a sensor.

Analysis engine Examines the collected network traffic and compares it to known patterns of suspicious or malicious activity stored in the signature database. The analysis engine is the “brains” of the IDS.

Signature database A collection of patterns and definitions of known suspicious or malicious activity.

User interface and reporting Interfaces with the human element,

providing alerts when appropriate and giving the user a means to interact with and operate the IDS.

Tech Tip

IDS Signatures An IDS relies heavily on its signature database just like antivirus products rely on their virus definitions. If an attack is something completely new, an IDS may not recognize the traffic as malicious.

Let’s look at an example to see how all these components work together. Imagine a network intruder is scanning your organization for systems running a web server. The intruder launches a series of network probes against every IP address in your organization. The traffic from the intruder comes into your network and passes through the traffic collector (sensor). The traffic collector forwards the traffic to the analysis engine. The analysis engine examines and categorizes the traffic—it identifies a large number of probes coming from the same outside IP address (the intruder). The analysis engine compares the observed behavior against the signature database and gets a match. The intruder’s activity matches a TCP port scan. The intruder is sending probes to many different systems in a short period of time. The analysis engine generates an alarm that is passed off to the user interface and reporting mechanisms. The user interface generates a notification to the administrator (icon, log entry, and so on). The administrator sees the alert and can now decide what to do about the potentially malicious traffic. Alarm storage is simply a repository of alarms the IDS has recorded—most IDS products allow administrators to run customized reports that sift through the collected alarms for items the administrator is searching for, such as all the alarms generated by a specific IP address.

Most IDSs can be tuned to fit a particular environment. Certain signatures can be turned off, telling the IDS not to look for certain types of traffic. For example, if you are operating in a pure UNIX environment, you may not wish to see Windows-based alarms, as they will not affect your systems. Additionally, the severity of the alarm levels can be adjusted depending on how concerned you are over certain types of traffic. Some IDSs also allow the user to exclude certain patterns of activity from specific hosts. In other words, you can tell the IDS to ignore the fact that some systems generate traffic that looks like malicious activity, because it really isn’t.

In addition to the network versus host distinction, some IDS vendors will further categorize an IDS based on how it performs the detection of suspicious or malicious traffic. The different models used are covered in the next section.

IDS Models In addition to being divided along the host and network lines, IDSs are often classified according to the detection model they use: anomaly or misuse. For an IDS, a model is a method for examining behavior so that the IDS can determine whether that behavior is “not normal” or in violation of established policies. An anomaly detection model is the more complicated of the two. In

this model, the IDS must know what “normal” behavior on the host or network being protected really is. Once the “normal” behavior baseline is established, the IDS can then go to work identifying deviations from the norm, which are further scrutinized to determine whether or not that activity is malicious. Building the profile of normal activity is usually done by the IDS, with some input from security administrators, and can take days to months. The IDS must be flexible and capable enough to account for things such as new systems, new users, movement of information resources, and other factors, but be sensitive enough to detect a single user illegally switching from one account to another at 3 A.M. on a Saturday.

Exam Tip: Anomaly detection looks for things that are out of the ordinary, such as a user logging in when he’s not supposed to or unusually high network traffic into and out of a workstation.

Anomaly detection was developed to make the system capable of dealing with variations in traffic and better able to determine which activity patterns were malicious. A perfectly functioning anomaly-based system would be able to ignore patterns from legitimate hosts and users but still identify those patterns as suspicious should they come from a potential attacker. Unfortunately, most anomaly-based systems suffer from extremely high false positives, especially during the “break-in” period while the IDS is learning the network. On the other hand, an anomaly- based system is not restricted to a specific signature set and is far more likely to identify a new exploit or attack tool that would go unnoticed by a traditional IDS.

Exam Tip: Misuse detection looks for things that violate policy, such as a denial-of-service attack launched at your web server or an attacker attempting to brute-force an SSH session.

A misuse detection model is a little simpler to implement, and therefore it’s the more popular of the two models. In a misuse detection model, the IDS looks for suspicious activity or activity that violates specific policies and then reacts as it has been programmed to do. This reaction can be an alarm, e-mail, router reconfiguration, or TCP reset message. Technically, misuse detection is the more efficient model, as it takes fewer resources to operate, does not need to learn what “normal” behavior is, and will generate an alarm whenever a pattern is successfully matched. However, the misuse model’s greatest weakness is its reliance on a predefined signature base—any activity, malicious or otherwise, that the

misuse-based IDS does not have a signature for will go undetected. Despite that drawback and because it is easier and cheaper to implement, most commercial IDS products are based on the misuse detection model. Some analysts break IDS models down even further into four categories

depending on how the IDS operates and detects malicious traffic (the same models can also be applied to intrusion prevention systems as well—both NIPS and HIPS):

Behavior-based This model relies on a collected set of “normal behavior”: what should happen on the network and is considered “normal” or “acceptable” traffic. Behavior that does not fit into the “normal” activity categories or patterns is considered suspicious or malicious. This model can potentially detect zero-day or unpublished attacks but carries a high false positive rate as any new traffic pattern can be labeled as “suspect.”

Signature-based This model relies on a predefined set of patterns (called signatures). The IDS has to know what behavior is considered “bad” ahead of time before it can identify and act upon suspicious or malicious traffic.

Anomaly-based This model is essentially the same as behavior-based. The IDS is first taught what “normal” traffic looks like and then looks for deviations to those “normal” patterns.

Heuristic This model uses artificial intelligence to detect intrusions and malicious traffic. A heuristic model is typically implemented through algorithms that help an IDS decide if a traffic pattern is malicious or not. For example, a URL containing 10 or more of the same repeating character may be considered “bad” traffic as a single signature. With a heuristic model, the IDS understands that if 10 repeating characters are bad, 11 are still bad, and 20 are even worse. This implementation of fuzzy logic allows this model to fall somewhere between signature-based and behavior-based models.

Signatures As you have probably deduced from the discussion so far, one of the critical elements of any good IDS is the signature database—the set of patterns the IDS uses to determine whether or not activity is potentially hostile. Signatures can be very simple or remarkably complicated, depending on the activity they are trying to highlight. In general, signatures can be divided into two main groups, depending on what the signature is looking for: content-based and context-based. Content-based signatures are generally the simplest. They are

designed to examine the content of such things as network packets or log entries. Content-based signatures are typically easy to build and look for simple things, such as a certain string of characters or a certain flag set in a TCP packet. Here are some example content-based signatures:

Matching the characters /etc/passwd in a Telnet session. On a UNIX system, the names of valid user accounts (and sometimes the passwords for those user accounts) are stored in a file called passwd located in the etc directory.

Matching the characters “to: decode” in the header of an e-mail message. On certain older versions of sendmail, sending an e-mail message to “decode” would cause the system to execute the contents of the e-mail.

Context-based signatures are generally more complicated, as they are designed to match large patterns of activity and examine how certain types of activity fit into the other activities going on around them. Context signatures generally address the question: How does this event compare to other events that have already happened or might happen in the near future? Context-based signatures are more difficult to analyze and take more resources to match, as the IDS must be able to “remember” past events to match certain context signatures. Here are some example context-based signatures:

Match a potential intruder scanning for open web servers on a specific network. A potential intruder may use a port scanner to look for any systems accepting connections on port 80. To match this signature, the IDS must analyze all attempted connections to port 80 and then be able to determine which connection attempts are coming from the same source but are going to multiple, different destinations.

Identify a Nessus scan. Nessus is an open-source vulnerability scanner that allows security administrators (and potential attackers) to quickly examine systems for vulnerabilities. Depending on the tests chosen, Nessus typically performs the tests in a certain order, one after the other. To be able to determine the presence of a Nessus scan, the IDS must know which tests Nessus runs as well as the typical order in which the tests are run.

Identify a ping flood attack. A single ICMP packet on its own is generally regarded as harmless, certainly not worthy of an IDS signature. Yet thousands of ICMP packets coming to a single system in a short period of time can have a devastating effect on the receiving system. By flooding a system with thousands of valid ICMP packets, an attacker can keep a target system so busy it doesn’t have time to do anything else—a very effective denial-of-service attack. To identify a ping flood, the IDS must recognize each ICMP packet and keep track of how many ICMP packets different systems have received in the recent past.

Exam Tip: Know the differences between content-based and context-based signatures. Content- based signatures match specific content, such as a certain string or series of characters (matching the string /etc/passwd in an FTP session). Context-based signatures match a pattern of activity based on the other activity around it, such as a port scan.

To function, the IDS must have a decent signature base with examples of known, undesirable activity that it can use when analyzing traffic or

events. Any time an IDS matches current events against a signature, the IDS could be considered successful, as it has correctly matched the current event against a known signature and reacted accordingly (usually with an alarm or alert of some type).

False Positives and False Negatives Viewed in its simplest form, an IDS is really just looking at activity (be it host-based or network-based) and matching it against a predefined set of patterns. When it matches activity to a specific pattern, the IDS cannot know the true intent behind that activity—whether it is benign or hostile— and therefore it can react only as it has been programmed to do. In most cases, this means generating an alert that must then be analyzed by a human who tries to determine the intent of the traffic from whatever information is available. When an IDS matches a pattern and generates an alarm for benign traffic, meaning the traffic was not hostile and not a threat, this is called a false positive. In other words, the IDS matched a pattern and raised an alarm when it didn’t really need to do so. Keep in mind that the IDS can only match patterns and has no ability to determine intent behind the activity, so in some ways this is an unfair label. Technically, the IDS is functioning correctly by matching the pattern, but from a human standpoint this is not information the analyst needed to see, as it does not constitute a threat and does not require intervention.

To reduce the generation of false positives, most administrators tune the IDS. “Tuning” an IDS is the process of configuring the IDS so that it works in your specific environment—generating alarms for malicious traffic and not generating alarms for traffic that is “normal” for your network. Effectively tuning an IDS can result in significant reductions in false-positive traffic.

An IDS is also limited by its signature set—it can match only activity for which it has stored patterns. Hostile activity that does not match an IDS signature and therefore goes undetected is called a false negative. In this

case, the IDS is not generating any alarms, even though it should be, giving a false sense of security.

Network-Based IDSs Network-based IDSs (NIDSs) actually came along a few years after host- based systems. After running host-based systems for a while, many organizations grew tired of the time, energy, and expense involved with managing the first generation of these systems—the host-based systems were not centrally managed, there was no easy way to correlate alerts between systems, and false-positive rates were high. The desire for a “better way” grew along with the amount of interconnectivity between systems and, consequently, the amount of malicious activity coming across the networks themselves. This fueled development of a new breed of IDS designed to focus on the source for a great deal of the malicious traffic— the network itself.

Tech Tip

Network Visibility A network IDS has to be able to see traffic to find the malicious traffic. Encrypted traffic such as SSH or HTTPS sessions must be decrypted before a network IDS can examine them.

The NIDS integrated very well into the concept of perimeter security. More and more companies began to operate their computer security like a castle or military base (see Figure 13.3), with attention and effort focused on securing and controlling the ways in and out—the idea being that if you could restrict and control access at the perimeter, you didn’t have to worry as much about activity inside the organization. Even though the idea of a security perimeter is somewhat flawed (many security incidents originate inside the perimeter), it caught on very quickly, as it was easy to understand and devices such as firewalls, bastion hosts, and routers were

available to define and secure that perimeter. The best way to secure the perimeter from outside attack is to reject all traffic from external entities, but this is impossible and impractical to do, so security personnel needed a way to let traffic in but still be able to determine whether or not the traffic was malicious. This is the problem that NIDS developers were trying to solve.

• Figure 13.3 Network perimeters are a little like castles—firewalls and NIDSs form the gates and guards to keep malicious traffic out.

As its name suggests, a NIDS focuses on network traffic—the bits and bytes traveling along the cables and wires that interconnect the systems. A NIDS must examine the network traffic as it passes by and be able to analyze traffic according to protocol, type, amount, source, destination, content, traffic already seen, and other factors. This analysis must happen quickly, and the NIDS must be able to handle traffic at whatever speed the network operates to be effective. NIDSs are typically deployed so that they can monitor traffic in and out

of an organization’s major links: connections to the Internet, remote offices, partners, and so on. Like host-based systems, NIDSs look for certain activities that typify hostile actions or misuse, such as the following:

Denial-of-service attacks

Port scans or sweeps

Malicious content in the data payload of a packet or packets

Vulnerability scanning

Trojans, viruses, or worms

Tunneling

Brute-force attacks

In general, most NIDSs operate in a fairly similar fashion. Figure 13.4 shows the logical layout of a NIDS. By considering the function and activity of each component, you can gain some insight into how a NIDS operates.

• Figure 13.4 Network IDS components

In the simplest form, a NIDS has the same major components: traffic collector, analysis engine, reports, and a user interface. In a NIDS, the traffic collector is specifically designed to pull traffic

from the network. This component usually behaves in much the same way as a network traffic sniffer—it simply pulls every packet it can see off the network to which it is connected. In a NIDS, the traffic collector will logically attach itself to a network interface card (NIC) and instruct the NIC to accept every packet it can. A NIC that accepts and processes every packet regardless of the packet’s origin and destination is said to be in promiscuous mode.

Tech Tip

Another Way to Look at NIDSs In its simplest form, a NIDS is a lot like a motion detector and a video surveillance system rolled into one. The NIDS notes the undesirable activity, generates an alarm, and records what happens.

The analysis engine in a NIDS serves the same function as its host- based counterpart, with some substantial differences. The network analysis engine must be able to collect packets and examine them individually or, if necessary, reassemble them into an entire traffic session. The patterns and signatures being matched are far more complicated than host-based signatures, so the analysis engine must be able to remember what traffic preceded the traffic currently being analyzed so that it can determine whether or not that traffic fits into a larger pattern of malicious activity. Additionally, the network-based analysis engine must be able to keep up with the flow of traffic on the network, rebuilding network sessions and matching patterns in real time.

Cross Check

NIDS and Encrypted Traffic You learned about encrypted traffic in Chapter 5, so check your memory with these questions. What is SSH? What is a one-time pad? Can you name at least three different algorithms?

The NIDS signature database is usually much larger than that of a host- based system. When examining network patterns, the NIDS must be able to recognize traffic targeted at many different applications and operating systems as well as traffic from a wide variety of threats (worms, assessment tools, attack tools, and so on). Some of the signatures themselves can be quite large, as the NIDS must look at network traffic

occurring in a specific order over a period of time to match a particular malicious pattern. Using the lessons learned from early host-based systems, NIDS

developers modified the logical component design somewhat to distribute the user interface and reporting functions. As many companies had more than one network link, they would need an IDS capable of handling multiple links in many different locations. The early IDS vendors solved this dilemma by dividing the components and assigning them to separate entities. The traffic collector, analysis engine, and signature database were bundled into a single entity, usually called a sensor or appliance. The sensors would report to and be controlled by a central system or master console. This central system, shown in Figure 13.5, consolidated alarms and provided the user interface and reporting functions that allowed users in one location to manage, maintain, and monitor sensors deployed in a variety of remote locations.

• Figure 13.5 Distributed network IDS components

By creating separate components designed to work together, the NIDS developers were able to build a more capable and flexible system. With encrypted communications, network sensors could be placed around both local and remote perimeters and still be monitored and managed securely from a central location. Placement of the sensors very quickly became an issue for most security personnel, as the sensors obviously had to have visibility of the network traffic in order to analyze it. Because most organizations with NIDSs also had firewalls, location of the NIDS relative to the firewall had to be considered as well. Placed before the firewall, as shown in Figure 13.6, the NIDS will see all traffic coming in from the

Internet, including attacks against the firewall itself. This includes traffic that the firewall stops and does not permit into the corporate network. With this type of deployment, the NIDS sensor will generate a large number of alarms (including alarms for traffic that the firewall would stop). This tends to overwhelm the human operators managing the system.

• Figure 13.6 NIDS sensor placed in front of firewall

Placed after the firewall, as shown in Figure 13.7, the NIDS sensor sees and analyzes the traffic that is being passed through the firewall and into the corporate network. While this does not allow the NIDS to see attacks against the firewall, it generally results in far fewer alarms and is the most popular placement for NIDS sensors.

• Figure 13.7 NIDS sensor placed behind firewall

As you already know, NIDSs examine the network traffic for suspicious or malicious activity. Here are two examples of suspicious traffic to illustrate the operation of a NIDS:

Port scan A port scan is a reconnaissance activity a potential attacker uses to find out information about the systems he wants to attack. Using any of a number of tools, the attacker attempts to connect to various services (web, FTP, SMTP, and so on) to see if they exist on the intended target. In normal network traffic, a single user might connect to the FTP service provided on a single system. During a port scan, an attacker may attempt to connect to the FTP service on every system. As the attacker’s traffic passes by the IDS, the IDS will notice this pattern of attempting to connect to different services on different systems in a relatively short period of time. When the IDS compares

the activity to its signature database, it will very likely match this traffic against the port scanning signature and generate an alarm.

Ping of death Toward the end of 1996, it was discovered that certain operating systems, such as Windows, could be crashed by sending a very large Internet Control Message Protocol (ICMP) echo request packet to that system. This is a fairly simple traffic pattern for a NIDS to identify, as it simply has to look for ICMP packets over a certain size.

Port scanning activity is rampant on the Internet. Most organizations with NIDS see hundreds or thousands of port scan alarms every day from sources around the world. Some administrators reduce the alarm level of port scan alarms or ignore port scanning traffic because there is simply too much traffic to track down and respond to each alarm.

Advantages of a NIDS A NIDS has certain advantages that make it a good choice for certain situations:

Providing IDS coverage requires fewer systems. With a few well- placed NIDS sensors, you can monitor all the network traffic going in and out of your organization. Fewer sensors usually equates to less overhead and maintenance, meaning you can protect the same number of systems at a lower cost.

Deployment, maintenance, and upgrade costs are usually lower. The fewer systems that have to be managed and maintained to provide IDS coverage, the lower the cost to operate the IDS. Upgrading and maintaining a few sensors is usually much cheaper than upgrading and maintaining hundreds of host-based processes.

A NIDS has visibility into all network traffic and can correlate attacks

among multiple systems. Well-placed NIDS sensors can see the “big picture” when it comes to network-based attacks. The network sensors can tell you whether attacks are widespread and unorganized or focused and concentrated on specific systems.

Disadvantages of a NIDS A NIDS has certain disadvantages:

It is ineffective when traffic is encrypted. When network traffic is encrypted from application to application or system to system, a NIDS sensor will not be able to examine that traffic. With the increasing popularity of encrypted traffic, this is becoming a bigger problem for effective IDS operations.

It can’t see traffic that does not cross it. The IDS sensor can examine only traffic crossing the network link it is monitoring. With most IDS sensors being placed on perimeter links, traffic traversing the internal network is never seen.

It must be able to handle high volumes of traffic. As network speeds continue to increase, the network sensors must be able to keep pace and examine the traffic as quickly as it can pass the network. When NIDSs were introduced, 10-Mbps networks were the norm. Now 100- Mbps and even 1-Gbps networks are commonplace. This increase in traffic speeds means IDS sensors must be faster and more powerful than ever before.

It doesn’t know about activity on the hosts themselves. NIDSs focus on network traffic. Activity that occurs on the hosts themselves will not be seen by a NIDS.

Tech Tip

TCP Reset The most common defensive ability for an active NIDS is to send a TCP reset message. Within TCP, the reset message (RST) essentially tells both sides of the connection to drop the session and stop communicating immediately. While this mechanism was originally developed to cover situations such as systems accidentally receiving communications intended for other systems, the reset message works fairly well for NIDSs—with one serious drawback: a reset message affects only the current session. Nothing prevents the attacker from coming back and trying again and again. Despite the “temporariness” of this solution, sending a reset message is usually the only defensive measure implemented on NIDS deployments, as the fear of blocking legitimate traffic and disrupting business processes, even for a few moments, often outweighs the perceived benefit of discouraging potential intruders.

Active vs. Passive NIDSs Most NIDSs can be distinguished by how they examine the traffic and whether or not they interact with that traffic. On a passive system, the NIDS simply watches the traffic, analyzes it, and generates alarms. It does not interact with the traffic itself in any way, and it does not modify the defensive posture of the system to react to the traffic. A passive NIDS is very similar to a simple motion sensor—it generates an alarm when it matches a pattern, much as the motion sensor generates an alarm when it sees movement. An active NIDS contains all the same components and capabilities of the passive NIDS with one critical addition—the active NIDS can react to the traffic it is analyzing. These reactions can range from something simple, such as sending a TCP reset message to interrupt a potential attack and disconnect a session, to something complex, such as dynamically modifying firewall rules to reject all traffic from specific source IP addresses for the next 24 hours.

NIDS Tools There are numerous examples of NIDS tools in the marketplace, from open source projects to commercial entries. Snort has been the de facto standard IDS engine since its creation in 1998. It has a large user base and

set the standard for many IDS element, including rule sets and formats. Snort rules are the list of activities that Snort will alert on and provide the flexible power behind the IDS platform. Snort rule sets are updated by a large active community as well as Sourcefire Vulnerability Research Team, the company behind Snort. Snort VRT rule sets are available to subscribers and provide such elements as same-day protection for items such as Microsoft patch Tuesday vulnerabilities. These rules are moved to the open community after 30 days. A newer entrant to the IDS marketplace is Suricata. Suricata is an open

source IDS, begun with grant money from the U.S. government and maintained by the Open Source Security Foundation (OSIF). Suricata has one advantage over Snort: it supports multithreading, while Snort only supports single-threaded operation. Both of these systems are highly flexible and scalable, operating on both Windows and Linux platforms.

Tech Tip

Snort Rules The basic format for Snort rules is a rule header followed by rule options.

Host-Based IDSs The very first IDSs were host-based and designed to examine activity only on a specific host. A host-based IDS (HIDS) examines log files, audit trails, and network traffic coming into or leaving a specific host. HIDSs can operate in real time, looking for activity as it occurs, or in batch mode, looking for activity on a periodic basis. Host-based systems are typically self-contained, but many of the newer commercial products have been designed to report to and be managed by a central system. Host-based

systems also take local system resources to operate. In other words, a HIDS will use up some of the memory and CPU cycles of the system it is protecting. Early versions of HIDSs ran in batch mode, looking for suspicious activity on an hourly or daily basis, and typically looked only for specific events in the system’s log files. As processor speeds increased, later versions of HIDSs looked through the log files in real time and even added the ability to examine the data traffic the host was generating and receiving. Most HIDSs focus on the log files or audit trails generated by the local

operating system. On UNIX systems, the examined logs usually include those created by syslog, such as messages, kernel logs, and error logs. On Windows systems, the examined logs are typically the three event logs: Application, System, and Security. Some HIDSs can cover specific applications, such as FTP or web services, by examining the logs produced by those specific applications or examining the traffic from the services themselves. Within the log files, the HIDS is looking for certain activities that typify hostile actions or misuse, such as the following:

Logins at odd hours

Login authentication failures

Additions of new user accounts

Modification or access of critical system files

Modification or removal of binary files (executables)

Starting or stopping processes

Privilege escalation

Use of certain programs

In general, most HIDSs operate in a very similar fashion. (Figure 13.8 shows the logical layout of a HIDS.) By considering the function and activity of each component, you can gain some insight into how HIDSs operate.

• Figure 13.8 Host-based IDS components

As on any IDS, the traffic collector on a HIDS pulls in the information the other components, such as the analysis engine, need to examine. For most HIDSs, the traffic collector pulls data from information the local system has already generated, such as error messages, log files, and system files. The traffic collector is responsible for reading those files, selecting which items are of interest, and forwarding them to the analysis engine. On some HIDSs, the traffic collector also examines specific attributes of critical files, such as file size, date modified, or checksum.

Critical files are those that are vital to the system’s operation or overall functionality. They may be program (or binary) files, files containing user accounts and passwords, or even scripts to start or stop system processes. Any unexpected modifications to these files could mean the system has

been compromised or modified by an attacker. By monitoring these files, the HIDS can warn users of potentially malicious activity.

The analysis engine is perhaps the most important component of the HIDS, as it must decide what activity is “okay” and what activity is “bad.” The analysis engine is a sophisticated decision and pattern-matching mechanism—it looks at the information provided by the traffic collector and tries to match it against known patterns of activity stored in the signature database. If the activity matches a known pattern, the analysis engine can react, usually by issuing an alert or alarm. An analysis engine may also be capable of remembering how the activity it is looking at right now compares to traffic it has already seen or may see in the near future, so that it can match more complicated, multistep malicious activity patterns. An analysis engine must also be capable of examining traffic patterns as quickly as possible, as the longer it takes to match a malicious pattern, the less time the HIDS or human operator has to react to malicious traffic. Most HIDS vendors build a decision tree into their analysis engines to expedite pattern matching. The signature database is a collection of predefined activity patterns

that have already been identified and categorized—patterns that typically indicate suspicious or malicious activity. When the analysis engine has an activity or traffic pattern to examine, it compares that pattern to the appropriate signatures in the database. The signature database can contain anywhere from a few to a few thousand signatures, depending on the vendor, type of HIDS, space available on the system to store signatures, and other factors. The user interface is the visible component of the HIDS—the part that

humans interact with. The user interface varies widely depending on the product and vendor and could be anything from a detailed GUI to a simple command line. Regardless of the type and complexity, the interface is provided to allow the user to interact with the system: changing parameters, receiving alarms, tuning signatures and response patterns, and so on.

Tech Tip

Decision Trees In computer systems, a tree is a data structure, each element of which is attached to one or more structures directly beneath it (the connections are called branches). Structures on the end of a branch without any elements below them are called leaves. Trees are most often drawn inverted, with the root at the top and all subsequent elements branching down from the root. Trees in which each element has no more than two elements below it are called binary trees. In IDSs, a decision tree is used to help the analysis engine quickly examine traffic patterns and eliminate signatures that don’t apply to the particular traffic or activity being examined, so that the fewest number of comparisons need to be made. For example, as shown in this illustration, the decision tree may contain a section that divides the activity into one of three subsections based upon the origin of the activity (a log entry for an event taken from the system logs, a file change for a modification to a critical file, or a user action for something a user has done):

When the analysis engine looks at the activity pattern and starts down the decision tree, it must decide which path to follow. If it is a log entry, the analysis engine can then concentrate on only the signatures that apply to log entries and it does not need to worry about signatures that apply to file changes or user actions. This type of decision tree allows the analysis engine to function much faster, as it does not have to compare activities to every signature in the database, just the signatures that apply to that particular type of activity. It is important to note that HIDSs can look at both activities occurring on the host itself and the network traffic coming into or leaving the host.

To better understand how a HIDS operates, take a look at the following examples from a UNIX system and a Windows system. On a UNIX system, the HIDS is likely going to examine any of a

number of system logs—basically, large text files containing entries about what is happening on the system. For this example, consider the following lines from the “messages” log on a Red Hat system:

In the first line beginning Jan 5, you see a session being opened by a user named bob. This usually indicates that whoever owns the account bob has logged into the system. On the next three lines beginning Jan 5, you see authentication failures as bob tries to become root—the superuser account that can do anything on the system. In this case, user bob tries three times

to become root and fails on each try. This pattern of activity could mean a number of different things—bob could be an admin who has forgotten the password for the root account, bob could be an admin and someone changed the root password without telling him, bob could be a user attempting to guess the root password, or an attacker could have compromised bob’s account and is now trying to compromise the root account on the system. In any case, our HIDS will work through its decision tree to determine whether an authentication failure in the message log is something it needs to examine. In this instance, when the HIDS examines these lines in the log, it will note the fact that three of the lines in the log match one of the patterns it has been told to look for (as determined by information from the decision tree and the signature database), and it will react accordingly, usually by generating an alarm or alert of some type that appears on the user interface or in an e-mail, page, or other form of message.

Tech Tip

Analyst-Driven Log Analysis Log analysis is the art of translating computer-generated logs into meaningful data. For example, a computer can’t always tell you if an administrator-level login at 3 A.M. on a Saturday is definitely a bad thing, but an analyst can. Human analysts can add value through the interpretation of information in context with other sources of information.

On a Windows system, the HIDS will likely examine the logs generated by the operating system. The three basic types of logs (Application, System, and Security) are similar to the logs on a UNIX system, though the Windows logs are not stored as text files and typically require a utility or application to read them. This example uses the Security log from a Windows Vista system:

In the first three main lines of the Security log, you see an Audit Failure entry for the Logon process. This indicates someone has tried to log into the system three times and has failed each time (much like our UNIX example) and then succeeded on the fourth try. You won’t see the name of the account until you expand the log entry within the Windows Event Viewer tool, but for this example, assume it was the administrator account —the Windows equivalent of the root account. Here again, you see three login failures—if the HIDS has been programmed to look for failed login attempts, it will generate alerts when it examines these log entries.

Advantages of HIDSs HIDSs have certain advantages that make them a good choice for certain situations:

They can be very operating system–specific and have more detailed signatures. A HIDS can be very specifically designed to run on a certain operating system or to protect certain applications. This narrow focus lets developers concentrate on the specific things that affect the specific environment they are trying to protect. With this type of focus, the developers can avoid generic alarms and develop much more specific, detailed signatures to identify malicious traffic more

accurately. They can reduce false-positive rates. When running on a specific system, the HIDS process is much more likely to be able to determine whether or not the activity being examined is malicious. By more accurately identifying which activity is “bad,” the HIDS will generate fewer false positives (alarms generated when the traffic matches a pattern but is not actually malicious).

They can examine data after it has been decrypted. With security concerns constantly on the rise, many developers are starting to encrypt their network communications. When designed and implemented in the right manner, a HIDS will be able to examine traffic that is unreadable to a network-based IDS. This particular ability is becoming more important each day as more and more web sites start to encrypt all of their traffic.

They can be very application specific. On a host level, the IDS can be designed, modified, or tuned to work very well on specific applications without having to analyze or even hold signatures for other applications that are not running on that particular system. Signatures can be built for specific versions of web server software, FTP servers, mail servers, or any other application housed on that host.

They can determine whether or not an alarm may impact that specific system. The ability to determine whether or not a particular activity or pattern will really affect the system being protected assists greatly in reducing the number of generated alarms. Because the HIDS resides on the system, it can verify things such as patch levels, presence of certain files, and system state when it analyzes traffic. By knowing what state the system is in, the HIDS can more accurately determine whether an activity is potentially harmful to the system.

Disadvantages of HIDSs

HIDSs also have certain disadvantages that must be weighed in making the decision of whether to deploy this type of technology:

The HIDS must have a process on every system you want to watch. You must have a HIDS process or application installed on every host you want to watch. To watch 100 systems, then, you would need to deploy 100 HIDSs, or remote agents.

The HIDS can have a high cost of ownership and maintenance. Depending on the specific vendor and application, a HIDS can be fairly costly in terms of time and manpower to maintain. Unless some type of central console is used that allows you to maintain remote processes, administrators must maintain each HIDS process individually. Even with a central console, with a HIDS, there will be a high number of processes to maintain, software to update, and parameters to tune.

The HIDS uses local system resources. To function, the HIDS must use CPU cycles and memory from the system it is trying to protect. Whatever resources the HIDS uses are no longer available for the system to perform its other functions. This becomes extremely important on applications such as high-volume web servers, where fewer resources usually means fewer visitors served and the need for more systems to handle expected traffic.

The HIDS has a very focused view and cannot relate to activity around it. The HIDS has a limited view of the world, as it can see activity only on the host it is protecting. It has little to no visibility into traffic around it on the network or events taking place on other hosts. Consequently, a HIDS can tell you only if the system it is running on is under attack.

The HIDS, if logging only locally, could be compromised or disabled. When a HIDS generates alarms, it typically stores the alarm information in a file or database of some sort. If the HIDS stores its generated alarm traffic on the local system, an attacker that is

successful in breaking into the system may be able to modify or delete those alarms. This makes it difficult for security personnel to discover the intruder and conduct any type of post-incident investigation. A capable intruder may even be able to turn off the HIDS process completely.

A security best practice is to store or make a copy of log information, especially security-related log information, on a separate system. When a system is compromised, the attacker typically hides their tracks by clearing out any log files on the compromised system. If the log files are only stored locally on the compromised system, you’ll know an attacker was present (due to the empty log files) but you won’t know what they did or when they did it.

Active vs. Passive HIDSs Most IDSs can be distinguished by how they examine the activity around them and whether or not they interact with that activity. This is certainly true for HIDSs. On a passive system, the HIDS is exactly that—it simply watches the activity, analyzes it, and generates alarms. It does not interact with the activity itself in any way, and it does not modify the defensive posture of the system to react to the traffic. A passive HIDS is similar to a simple motion sensor—it generates an alarm when it matches a pattern, much as the motion sensor generates an alarm when it sees movement. An active IDS will contain all the same components and capabilities of

the passive IDS with one critical exception—the active IDS can react to the activity it is analyzing. These reactions can range from something simple, such as running a script to turn a process on or off, to something as complex as modifying file permissions, terminating the offending processes, logging off specific users, and reconfiguring local capabilities to prevent specific users from logging in for the next 12 hours.

Resurgence and Advancement of HIDSs

The past few years have seen a strong resurgence in the use of HIDSs. With the great advances in processor power, the introduction of multicore processors, and the increased capacity of hard drives and memory systems, some of the traditional barriers to running a HIDS have been overcome. Combine those advances in technology with the widespread adoption of always-on broadband connections, the rise in the use of telecommuting, and a greater overall awareness of the need for computer security, and solutions such as HIDSs start to become an attractive and sometimes effective solution for business and home users alike. The latest generation of HIDSs has introduced new capabilities designed

to stop attacks by preventing them from ever executing or accessing protected files in the first place, rather than relying on a specific signature set that only matches known attacks. The more advanced host-based offerings, which most vendors refer to as host-based intrusion prevention systems (HIPSs), combine the following elements into a single package:

Integrated system firewall The firewall component checks all network traffic passing into and out of the host. Users can set rules for what types of traffic they want to allow into or out of their system.

Behavioral- and signature-based IDS This hybrid approach uses signatures to match well-known attacks and generic patterns for catching “zero-day” or unknown attacks for which no signatures exist.

Application control This allows administrators to control how applications are used on the system and whether or not new applications can be installed. Controlling the addition, deletion, or modification of existing software can be a good way to control a system’s baseline and prevent malware from being installed.

Enterprise management Some host-based products are installed with an “agent” that allows them to be managed by and report back to a central server. This type of integrated remote management capability is essential in any large-scale deployment of host-based IDS/IPS.

Malware detection and prevention Some HIDSs/HIPSs include

scanning and prevention capabilities that address spyware, malware, rootkits, and other malicious software.

Integrated security products can provide a great deal of security-related features in a single package. This is often cheaper and more convenient than purchasing a separate antivirus product, a firewall, and an IDS. However, integrated products are not without potential pitfalls—if one portion of the integrated product fails, the entire protective suite may fail. Symantec’s Endpoint Protection and McAfee’s Internet Security are examples of integrated, host-based protection products.

Intrusion Prevention Systems An intrusion prevention system (IPS) monitors network traffic for malicious or unwanted behavior and can block, reject, or redirect that traffic in real time. Sound familiar? It should: while many vendors will argue that an IPS is a different animal from an IDS, the truth is that most IPSs are merely expansions of existing IDS capabilities. As a core function, an IPS must be able to monitor for and detect potentially malicious network traffic, which is essentially the same function as an IDS. However, an IPS does not stop at merely monitoring traffic—it must be able to block, reject, or redirect that traffic in real time to be considered a true IPS. It must be able to stop or prevent malicious traffic from having an impact. To qualify as an IDS, a system just needs to see and classify the traffic as malicious. To qualify as an IPS, a system must be able to do something about that traffic. In reality, most products that are called IDSs, including the first commercially available IDS, NetRanger, can interact with and stop malicious traffic, so the distinction between the two is often blurred.

The term intrusion prevention system was originally coined by Andrew Plato in marketing literature developed for NetworkICE, a company that was purchased by ISS and which is now part of IBM. The term IPS has effectively taken the place of the term “active IDS.”

Like IDSs, most IPSs have an internal signature database to compare network traffic against known “bad” traffic patterns. IPSs can perform content-based inspections, looking inside network packets for unique packets, data values, or patterns that match known malicious patterns. Some IPSs can perform protocol inspection, in which the IPS decodes traffic and analyzes it as it would appear to the server receiving it. For example, many IPSs can do HTTP protocol inspection, so they can examine incoming and outgoing HTTP traffic and process it as an HTTP server would. The advantage here is that the IPS can detect and defeat popular evasion techniques such as encoding URLs because the IPS “sees” the traffic in the same way the web server would when it receives and decodes it. The IPS can also detect activity that is abnormal or potentially malicious for that protocol, such as passing an extremely large value (over 10,000 characters) to a login field on a web page.

Exam Tip: An IDS is like a burglar alarm—it watches and alerts you when something bad happens. An IPS is like an armed security guard—it watches, stops the bad activity, and then lets you know what happened.

Unlike a traditional IDS, an IPS must sit inline (in the flow of traffic) to be able to interact effectively with the network traffic. Most IPSs can operate in “stealth mode” and do not require an IP address for the connections they are monitoring. When an IPS detects malicious traffic, it can drop the offending packets, reset incoming or established connections, generate alerts, quarantine traffic to/from specific IP addresses, or even block traffic from offending IP addresses on a temporary or permanent basis. As they are sitting inline, most IPSs can also offer rate-based monitoring to detect and mitigate denial-of-service attacks. With rate-

based monitoring, the IPS can watch the amount of traffic traversing the network. If the IPS sees too much traffic coming into or going out from a specific system or set of systems, the IPS can intervene and throttle down the traffic to a lower and more acceptable level. Many IPSs perform this function by “learning” what are “normal” network traffic patterns with regard to number of connections per second, amount of packets per connection, packets coming from or going to specific ports, and so on, and comparing current traffic rates for network traffic (TCP, UDP, ARP, ICMP, and so on) to those established norms. When a traffic pattern reaches a threshold or varies dramatically from those norms, the IPS can react and intervene as needed.

Tech Tip

Inline Network Devices An “inline” network device is something that is positioned in the flow of traffic—network traffic must pass through it going into or out of the network. Any inline device has the potential to stop network traffic if that device fails. To allow network traffic to flow, many network devices will fail “open,” meaning they simply pass traffic from one interface to another without inspecting it or interacting with it. Some administrators choose to have their firewalls and IPSs fail “closed,” meaning that if the devices are not functioning correctly, all traffic is stopped until those devices can be repaired.

Like a traditional IDS, the IPS has a potential weakness when dealing with encrypted traffic. Traffic that is encrypted will typically pass by the IPS untouched (provided it does not trigger any non-content–related alarms such as rate-based alarms). To counter this problem, some IPS vendors are including the ability to decrypt Secure Sockets Layer (SSL) sessions for further inspection. To do this, some IPS solutions store copies of any protected web servers’ private keys on the sensor itself. When the IPS sees a session initiation request, it monitors the initial transactions between the server and the client. By using the server’s stored private keys, the IPS will be able to determine the session keys negotiated during

the SSL session initiation. With the session keys, the IPS can decrypt all future packets passed between server and client during that web session. This gives the IPS the ability to perform content inspection on SSL- encrypted traffic.

The term wire speed refers to the theoretical maximum transmission rate of a cable or other medium and is based on a number of factors, including the properties of the cable itself and the connection protocol in use (in other words, how much data can be pushed through under ideal conditions).

You will often see IPSs (and IDSs) advertised and marketed by the amount of traffic they can process without dropping packets or interrupting the flow of network traffic. In reality, a network will never reach its hypothetical maximum transmission rate, or wire speed, due to errors, collisions, retransmissions, and other factors; therefore, a 1-Gbps network is not actually capable of passing 1 Gbps of network traffic, even if all the components are rated to handle 1 Gbps. When used in a marketing sense, wire speed is the maximum throughput rate the networking or security device equipment can process without impacting that network traffic. For example, a 1-Gbps IPS should be able to process, analyze, and protect 1 Gbps of network traffic without impacting traffic flow. IPS vendors often quote their products’ capacity as the combined throughput possible through all available ports on the IPS sensor—a 10-Gbps sensor may have 12 Gigabit Ethernet ports but is capable of handling only 10 Gbps of network traffic.

Tech Tip

Detection Controls vs. Prevention Controls When securing your organization, especially your network perimeter and critical systems, you will likely have to make some choices as to what type of protective measures and controls you need to implement. For example, you may need to decide between detection controls

(capabilities that detect and alert on suspicious or malicious activity) and prevention controls (capabilities that stop suspicious or malicious activity). Consider the differences between a traditional IDS and IPS. Although many IDSs have some type of response capability, their real purpose is to watch for activity and then alert when “hostile” activity is noted. On the other hand, an IPS is designed to block, thwart, and prevent that same “hostile” activity. A parallel example in the physical security space would be a camera and a security guard.

A camera watches activity and can even generate alerts when motion is detected. But a camera cannot stop an intruder from breaking into a facility and stealing something—it only records and alerts. A security guard, however, has the ability to stop the intruder physically, either before they break into the facility or before they can leave with the stolen goods.

Honeypots and Honeynets As is often the case, one of the best tools for information security personnel has always been knowledge. To secure and defend a network and the information systems on that network properly, security personnel need to know what they are up against. What types of attacks are being used? What tools and techniques are popular at the moment? How effective is a certain technique? What sort of impact will this tool have on my network? Often this sort of information is passed through white papers, conferences, mailing lists, or even word of mouth. In some cases, the tool developers themselves provide much of the information in the interest of promoting better security for everyone. Information is also gathered through examination and forensic analysis,

often after a major incident has already occurred and information systems are already damaged. One of the most effective techniques for collecting this type of information is to observe activity firsthand—watching an attacker as he probes, navigates, and exploits his way through a network. To accomplish this without exposing critical information systems, security researchers often use something called a honeypot. A honeypot, sometimes called a digital sandbox, is an artificial

environment where attackers can be contained and observed without putting real systems at risk. A good honeypot appears to an attacker to be a real network consisting of application servers, user systems, network

traffic, and so on, but in most cases it’s actually made up of one or a few systems running specialized software to simulate the user and network traffic common to most targeted networks. Figure 13.9 illustrates a simple honeypot layout in which a single system is placed on the network to deliberately attract attention from potential attackers.

• Figure 13.9 Logical depiction of a honeypot

Figure 13.9 shows the security researcher’s view of the honeypot, while Figure 13.10 shows the attacker’s view. The security administrator knows that the honeypot, in this case, actually consists of a single system running software designed to react to probes, reconnaissance attempts, and exploits as if it were an entire network of systems. When the attacker connects to the honeypot, she is presented with an entire “virtual” network of servers and PCs running a variety of applications. In most cases, the honeypot will

appear to be running versions of applications that are known to be vulnerable to specific exploits. All this is designed to provide the attacker with an enticing, hopefully irresistible, target.

• Figure 13.10 Virtual network created by the honeypot

Any time an attacker has been lured into probing or attacking the virtual network, the honeypot records the activity for later analysis: what the attacker does, which systems and applications she concentrates on, what

tools are run, how long the attacker stays, and so on. All this information is collected and analyzed in the hopes that it will allow security personnel to better understand and protect against the threats to their systems. There are many honeypots in use, specializing in everything from

wireless to denial-of-service attacks; most are run by research, government, or law enforcement organizations. Why aren’t more businesses running honeypots? Quite simply, the time and cost are prohibitive. Honeypots take a lot of time and effort to manage and maintain, and even more effort to sort, analyze, and classify the traffic the honeypot collects. Unless they are developing security tools, most companies focus their limited security efforts on preventing attacks, and in many cases, companies aren’t even that concerned with detecting attacks as long as the attacks are blocked, are unsuccessful, and don’t affect business operations. Even though honeypots can serve as a valuable resource by luring attackers away from production systems and allowing defenders to identify and thwart potential attackers before they cause any serious damage, the costs and efforts involved deter many companies from using honeypots. A honeynet is a collection of two or more honeypots. Larger, very

diverse network environments can deploy multiple honeypots (thus forming a honeynet) when a single honeypot device does not provide enough coverage. Honeynets are often integrated into an organization- wide IDS/IPS because the honeynet can provide relevant information about potential attackers.

Exam Tip: A honeypot is a system designed to attract potential attackers by pretending to be one or more systems with open network services.

Tools

Tools are a vital part of any security professional’s skill set. You may not be an “assessment professional” who spends most of his or her career examining networks looking for vulnerabilities, but you can use many of the same tools for internal assessment activities, tracking down infected systems, spotting inappropriate behavior, and so on. Knowing the right tool for the job can be critical to performing effectively.

Protocol Analyzer A protocol analyzer (also known as a packet sniffer, network analyzer, or network sniffer) is a piece of software or an integrated software/hardware system that can capture and decode network traffic. Protocol analyzers have been popular with system administrators and security professionals for decades because they are such versatile and useful tools for a network environment. From a security perspective, protocol analyzers can be used for a number of activities, such as the following:

Detecting intrusions or undesirable traffic (an IDS/IPS must have some type of capture and decode ability to be able to look for suspicious/malicious traffic)

Capturing traffic during incident response or incident handling

Looking for evidence of botnets, Trojans, and infected systems

Looking for unusual traffic or traffic exceeding certain thresholds

Testing encryption between systems or applications

From a network administration perspective, protocol analyzers can be used for activities such as these:

Analyzing network problems

Detecting misconfigured applications or misbehaving applications

Gathering and reporting network usage and traffic statistics

Debugging client/server communications

Exam Tip: A sniffer must use a NIC placed in promiscuous (promisc) mode or it will not see all the network traffic coming into the NIC.

Regardless of the intended use, a protocol analyzer must be able to see network traffic in order to capture and decode it. A software-based protocol analyzer must be able to place the NIC it is going to use to monitor network traffic in promiscuous mode (sometimes called promisc mode). Promiscuous mode tells the NIC to process every network packet it sees regardless of the intended destination. Normally, a NIC processes only broadcast packets (which go to everyone on that subnet) and packets with the NIC’s Media Access Control (MAC) address as the destination address inside the packet. As a sniffer, the analyzer must process every packet crossing the wire, so the ability to place a NIC into promiscuous mode is critical. With older networking technologies, such as hubs, it was easier to

operate a protocol analyzer, as the hub broadcasted every packet across every interface regardless of the destination. With switches now the standard for networking equipment, placing a protocol analyzer becomes more difficult as switches do not broadcast every packet across every port. While this may make it harder for administrators to sniff the traffic, it also makes it harder for eavesdroppers and potential attackers. To accommodate protocol analyzers, IDS devices, and IPS devices,

most switch manufacturers support port mirroring or a Switched Port Analyzer (SPAN) port (discussed in the next section). Depending on the manufacturer and the hardware, a mirrored port will see all the traffic passing through the switch or through a specific VLAN(s), or all the traffic passing through other specific switch ports. The network traffic is essentially copied (or mirrored) to a specific port, which can then support a protocol analyzer.

Another option for traffic capture is to use a network tap, a hardware device that can be placed inline on a network connection and that will copy traffic passing through the tap to a second set of interfaces on the tap. Network taps are often used to sniff traffic passing between devices at the network perimeter, such as the traffic passing between a router and a firewall. Many common network taps work by bridging a network connection and passing incoming traffic out one tap port (A) and outgoing traffic out another tap port (B), as shown in Figure 13.11.

• Figure 13.11 A basic network tap

A popular, open source protocol analyzer is Wireshark (www.wireshark.org). Available for both UNIX and Windows operating systems, Wireshark is a GUI-based protocol analyzer that allows users to capture and decode network traffic on any available network interface in the system on which the software is running (including wireless interfaces), as demonstrated in Figure 13.12. Wireshark has some interesting features, including the ability to “follow the TCP stream,” which allows the user to select a single TCP packet and then see all the other packets involved in that TCP conversation.

• Figure 13.12 Wireshark—a popular, open source protocol analyzer

Switched Port Analyzer The term Switched Port Analyzer (SPAN) is usually associated with Cisco switches—other vendors refer to the same capability as port mirroring or port monitoring. A SPAN has the ability to copy network traffic passing through one or more ports on a switch or one or more VLANs on a switch and forward that copied traffic to a port designated for traffic capture and analysis (as shown in Figure 13.13). A SPAN port or mirror port creates the collection point for traffic that will be fed into a protocol analyzer or IDS/IPS. SPAN or mirror ports can usually be configured to monitor traffic passing into interfaces, passing out of interfaces, or passing in both directions. When configuring port mirroring, you need to be aware of the capabilities of the switch you are working with. Can it handle the volume of traffic? Can it successfully mirror all the traffic, or will it end up dropping packets to the SPAN if traffic volume gets too high?

• Figure 13.13 A SPAN port collects traffic from other ports on a switch.

Port Scanner A port scanner is a tool designed to probe a system or systems for open ports. Its job is to probe for open (or listening) ports and report back to the user which ports are closed, which are filtered, and which are open. Port scanners are available for virtually every operating system and almost every popular mobile computing platform—from tablets to smartphones. Having a good port-scanning tool in your toolset and knowing how to use it can be very beneficial. The good news/bad news about port scanners is that the “bad guys” use them for basically the same reasons the good guys use them. Port scanners can be used to do the following:

Search for “live” hosts on a network. Most port scanners enable you

to perform a quick scan using ICMP, TCP, or UDP packets to search for active hosts on a given network or network segment. ICMP is still very popular for this task, but with the default blocking of ICMP v4 in many modern operating systems, such as Windows 7 and beyond, users are increasingly turning to TCP or UDP scans for these tasks.

Search for any open ports on the network. Port scanners are most often used to identify any open ports on a host, group of hosts, or network. By scanning a large number of ports over a large number of hosts, a port scanner can provide you (or an attacker) with a very good picture of what services are running on which hosts on your network. Scans can be done for the “default” set of popular ports, a large range of ports, or every possible port (from 1 to 65535).

Search for specific ports. Only looking for web servers? Mail servers? Port scanners can also be configured to just look for specific services.

Identify services on ports. Some port scanners can help identify the services running on open ports based on information returned by the service or the port/service assigned (if standards have been followed). For example, a service running on port 80 is likely to be a web server.

Look for TCP/UDP services. Most port scanners can perform scans for both TCP and UDP services, although some tools do not allow you to scan for both protocols at the same time.

As a security professional, you’ll use port scanners in much the same way an attacker would: to probe the systems in your network for open services. When you find open services, you’ll need to determine if those services should be running at all, if they should be running on the system(s) you found them on, and if you can do anything to limit what connections are allowed to those services. For example, you may want to scan your network for any system accepting connections on TCP port 1433 (Microsoft SQL Server). If you find a system accepting connections on TCP port 1433 in your Sales group, chances are someone has installed something they shouldn’t have (or someone installed something for them).

So how does a port scanner actually work? Much will depend on the options you select when configuring your scan, but for the sake of this example, assume you’re running a standard TCP connect scan against 192.168.1.20 for ports 1–10000. The scanner will attempt to create a TCP connection to each port in the range 1–10000 on 192.168.1.20. When the scanner sends out that SYN packet, it waits for the responding SYN/ACK. If a SYN/ACK is received, the scanner will attempt to complete the three- way handshake and mark the port as “open.” If the sent packet times out or an RST packet is received, the scanner will likely mark that port as “closed.” If an “administratively prohibited” message or something similar comes back, the scanner may mark that port as “filtered.” When the scan is complete, the scanner will present the results in a summary format—listing the ports that are open, closed, filtered, and so on. By examining the responses from each port, you can typically deduce a bit more information about the system(s) you are scanning, as detailed here:

Open Open ports accept connections. If you can connect to these with a port scanner, the ports are not being filtered at the network level. However, there are instances where you may find a port that is marked as “open” by a port scanner that will immediately drop your connections if you attempt to connect to it in some other manner. For example, port 22 for SSH may appear “open” to a port scanner but will immediately drop your SSH connections. In such a case, the service is likely being filtered by a host-based firewall or a firewall capability within the service itself.

Closed You will typically see this response when the scanned target returns an RST packet.

Filtered You will typically see this response when an ICMP unreachable error is returned. This usually indicates that port is being filtered by a firewall or other device.

Additional types Some port scanners will attempt to further classify responses, such as dropped, blocked, denied, timeout, and so on.

These are fairly tool specific, and you should refer to any documentation or help file that accompanies that port scanner for additional information.

In general, you will want to run your scanning efforts multiple times using different options to ensure you get a better picture. A SYN scan may return different results than a NULL scan or FIN scan. You’ll want to run both TCP and UDP scans as well. You may need to alter your scanning approach to use multiple techniques at different times of the day/night to ensure complete coverage. The bad guys are doing this against your network right now, so you might as well use the same tools they do to see what they see. Port scanners can also be very useful for testing firewall configurations because the results of the port scans can show you exactly which ports are open, which ones you allow through, which ports are carrying services, and so on. So how do you defend against port scans? Well, it’s tough. Port scans

are pretty much a part of the Internet traffic landscape now. Although you can block IP addresses that scan you, most organizations don’t because you run the risk of an attacker spoofing source addresses as decoys for other scanning activity. The best defense is to carefully control what traffic you let in and out of your network, using firewalls, network filters, and host filters. Then carefully monitor any traffic that you do allow in.

Passive vs. Active Tools Tools can be classified as active or passive. Active tools interact with a target system in a fashion where their use can be detected. Scanning a network with Nmap (Network Mapper) is an active act that can be detected. In the case of Nmap, the tool may not be specifically detectable, but its use, the sending of packets, can be detected. When you need to map out your network or look for open services on one or more hosts, a port scanner is probably the most efficient tool for the job. Figure 13.14 shows a screen shot of Zenmap, a cross-platform version of the very popular Nmap port scanner available from http://insecure.org.

• Figure 13.14 Zenmap—a port scanner based on Nmap

Passive tools are those that do not interact with the system in a manner that would permit detection, as in sending packets or altering traffic. An example of a passive tool is Tripwire, which can detect changes to a file based on hash values. Another passive example is the OS mapping by analyzing TCP/IP traces with a tool such as Wireshark. Passive sensors can use existing traffic to provide data for analysis.

Exam Tip: Passive tools receive traffic only and do nothing to the traffic flow that would permit others to know they are interacting with the network. Active tools modify or send traffic and are thus discoverable by their traffic patterns.

Banner Grabbing Banner grabbing is a technique used to gather information from a service that publicizes information via a banner. Banners can be used for many things; for example, they can be used to identify services by type, version, and so forth, and they enable administrators to post information, including warnings, to users when they log in. Attackers can use banners to determine what services are running, and typically do for common banner- issuing services such as HTTP, FTP, SMTP, and Telnet. Figure 13.15 shows a couple of banner grabs being performed from a Telnet client against a web server. In this example, Telnet sends information to two different web servers and displays the responses (the banners). The top response is from an Apache instance (Apache/2.0.65) and the bottom is from Microsoft IIS (Microsoft-HTTPAPI/2.0).

• Figure 13.15 Banner grabbing using Telnet

Chapter 13 Review

For More Information SANS Intrusion Detection FAQ www.sans.org/security- resources/idfaq/

SANS Reading Room—Firewalls & Perimeter Protection www.sans.org/reading_room/whitepapers/firewalls/

The Honeynet Project www.honeynet.org Fight Spam on the Internet! http://spam.abuse.net/

Lab Manual Exercises The following lab exercises from the companion lab manual, Principles of Computer Security Lab Manual, Fourth Edition, provide practical application of material covered in this chapter:

Chapter Summary After reading this chapter and completing the exercises, you should understand the following facts about intrusion detection systems and network security.

Apply the appropriate network tools to facilitate network security

Intrusion detection is a mechanism for detecting unexpected or unauthorized activity on computer systems.

IDSs can be host-based, examining only the activity applicable to a specific system, or network-based, examining network traffic for a large number of systems.

Protocol analyzers, often called sniffers, are tools that capture and decode network traffic.

Honeypots are specialized forms of intrusion detection that involve setting up simulated hosts and services for attackers to target.

Honeypots are based on the concept of luring attackers away from legitimate systems by presenting more tempting or interesting systems that, in most cases, appear to be easy targets.

Determine the appropriate use of tools to facilitate network security

IDSs match patterns known as signatures that can be content- or context-based. Some IDSs are model-based and alert an administrator when activity does not match normal patterns (anomaly-based) or when it matches known suspicious or malicious patterns (misuse detection).

Newer versions of IDSs include prevention capabilities that automatically block suspicious or malicious traffic before it reaches its intended destination. Most vendors call these intrusion prevention systems (IPSs).

Analyzers must be able to see and capture network traffic to be effective, and many switch vendors support network analysis through the use of mirroring or SPAN ports.

Network traffic can also be viewed using network taps, a device for replicating network traffic passing across a physical link.

By monitoring activity within the honeypot, security personnel are better able to identify potential attackers along with their tools and capabilities.

Apply host-based security applications

Host-based IDSs can apply specific context-sensitive rules because of the known host role.

Host-based IPSs can provide better control over specific attacks as the scope of control is limited to a host.

Key Terms analysis engine (379) anomaly detection model (379) banner grabbing (403) content-based signature (381) context-based signature (381) digital sandbox (396) false negative (382) false positive (382) honeynet (397) honeypot (396) host-based IDS (HIDS) (378) intrusion detection system (IDS) (376) intrusion prevention system (IPS) (394) misuse detection model (380) network tap (399) network-based IDS (NIDS) (378) perimeter security (383) port mirroring (399) protocol analyzer (398) signature database (379) Snort (387) Suricata (387)

Switched Port Analyzer (SPAN) (400) traffic collector (378) user interface and reporting (379)

Key Terms Quiz Use terms from the Key Terms list to complete the sentences that follow. Don’t use the same term more than once. Not all terms will be used.

1. A(n) _______________ is a piece of software or an integrated software/hardware system that can capture and decode network traffic.

2. When an IDS generates an alarm on “normal” traffic that is actually not malicious or suspicious, that alarm is called a(n) _______________.

3. An attacker scanning a network full of inviting, seemingly vulnerable targets might actually be scanning a(n) _______________ where the attacker’s every move can be watched and monitored by security administrators.

4. A(n) _______________ looks at a certain string of characters inside a TCP packet.

5. An IDS that looks for unusual or unexpected behavior is using a(n) _______________.

6. _______________ allows administrators to send all traffic passing through a network switch to a specific port on the switch.

7. Within an IDS, the _______________ examines the collected network traffic and compares it to known patterns of suspicious or malicious activity stored in the signature database.

8. _______________ is a technique where a host is queried and identified based on its response to a query.

9. _______________ is a technique to match an element against a large set of patterns and use activity as a screening element.

10. _______________ is a new entry in the IDS toolset as a replacement for Snort.

Multiple-Choice Quiz 1. What are the two main types of intrusion detection systems?

A. Network-based and host-based

B. Signature-based and event-based

C. Active and reactive

D. Intelligent and passive

2. What are the two main types of IDS signatures? A. Network-based and file-based

B. Context-based and content-based

C. Active and reactive

D. None of the above

3. Which of the following describes a passive, host-based IDS? A. Runs on the local system

B. Does not interact with the traffic around it

C. Can look at system event and error logs

D. All of the above

4. Which of the following is not a capability of network-based IDS? A. Can detect denial-of-service attacks

B. Can decrypt and read encrypted traffic

C. Can decode UDP and TCP packets

D. Can be tuned to a particular network environment

5. An active IDS can: A. Respond to attacks with TCP resets

B. Monitor for malicious activity

C. A and B

D. None of the above

6. Honeypots are used to: A. Attract attackers by simulating systems with open network

services

B. Monitor network usage by employees

C. Process alarms from other IDSs

D. Attract customers to e-commerce sites

7. Connecting to a server and sending a request over a known port in an attempt to identify the version of a service is an example of:

A. Port sniffing

B. Protocol analysis

C. Banner grabbing

D. TCP reset

8. Preventative intrusion detection systems: A. Are cheaper

B. Are designed to stop malicious activity from occurring

C. Can only monitor activity

D. Were the first types of IDS

9. IPS stands for: A. Intrusion processing system

B. Intrusion prevention sensor

C. Intrusion prevention system

D. Interactive protection system

10. A protocol analyzer can be used to: A. Troubleshoot network problems

B. Collect network traffic statistics

C. Monitor for suspicious traffic

D. All of the above

Essay Quiz 1. Discuss the differences between an anomaly-based and a misuse-

based detection model. Which would you use to protect a corporate network of 10,000 users? Why would you choose that model?

2. Pick three technologies discussed in this chapter and describe how you would deploy them to protect a small business network. Describe the protection each technology provides.

Lab Projects

• Lab Project 13.1

Design three content-based and three context-based signatures for use in an IDS. Name each signature and describe what the signature should look for, including traffic patterns or characters that need to be matched. Describe any activity that could generate a false positive for each signature.

• Lab Project 13.2 Use the Internet to research Snort (an open source IDS). With your instructor’s permission, download Snort and install it on your classroom network. Examine the traffic and note any alarms that are generated. Research and note the sources of the alarm traffic. See if you can track down the sources of the alarm traffic and discover why they are generating those alarms on your IDS.

chapter 14 System Hardening and Baselines

People can have the Model T in any color—so long as it’s black.

—HENRY FORD

T

In this chapter, you will learn how to

Harden operating systems and network operating systems

Implement host-level security

Harden applications

Establish group policies

Secure alternative environments (SCADA, real-time, etc.)

he many uses for systems and operating systems require flexible components that allow users to design, configure, and implement the systems they need. Yet it is this very flexibility that causes some of the

biggest weaknesses in computer systems. Computer and operating system developers often build and deliver systems in “default” modes that do little to secure the system from external attacks. From the view of the developer, this is the most efficient mode of delivery, as there is no way they can anticipate what every user in every situation will need. From the user’s view, however, this means a good deal of effort must be put into protecting and securing the system before it is ever placed into service. The process of securing and preparing a system for the production environment is called hardening. Unfortunately, many users don’t understand the steps necessary to secure their systems effectively, resulting in hundreds of compromised systems every day. Hardening systems, servers, workstations, networks, and applications is

a process of defining the required uses and needs and aligning security controls to limit a system’s desired functionality. Once this is determined, you have a system baseline that you can compare changes to over the course of a system’s lifecycle.

Overview of Baselines To secure systems effectively and consistently, you must take a structured

and logical approach. This starts with an examination of the system’s intended functions and capabilities to determine what processes and applications will be housed on the system. As a best practice, anything that is not required for operations should be removed or disabled on the system; then, all the appropriate patches, hotfixes, and settings should be applied to protect and secure it. This process of establishing a system’s security state is called

baselining, and the resulting product is a security baseline that allows the system to run safely and securely. Once the process has been completed for a particular hardware and software combination, any similar systems can be configured with the same baseline to achieve the same level and depth of security and protection. Uniform baselines are critical in large- scale operations, because maintaining separate configurations and security levels for hundreds or thousands of systems is far too costly. After administrators have finished patching, securing, and preparing a

system, they often create an initial baseline configuration. This represents a secure state for the system or network device and a reference point that can be used to help keep the system secure. If this initial baseline can be replicated, it can also be used as a template when deploying similar systems and network devices. Constructing a baseline or hardened system is similar for servers,

workstations, and network OSs. The specifics may vary, but the objects are the same.

Operating System and Network Operating System Hardening

The operating system (OS) of a computer is the basic software that handles things such as input, output, display, memory management, and all the other highly detailed tasks required to support the user environment and associated applications. Most users are familiar with the Microsoft family of desktop operating systems: Windows Vista, Windows 7,

Windows 8, and Windows 10. Indeed, the vast majority of home and business PCs run some version of a Microsoft operating system. Other users may be familiar with Mac OS X, Solaris, or one of the many varieties of the UNIX/Linux operating system. A network operating system (NOS) is an operating system that

includes additional functions and capabilities to assist in connecting computers and devices, such as printers, to a local area network (LAN). Some of the more familiar network operating systems include Novell’s NetWare and PC Micro’s LANtastic. For most modern operating systems, including Windows 2008, Solaris, and Linux, the terms operating system and network operating system are used interchangeably as they perform all the basic functions and provide enhanced capabilities for connecting to LANs.

Tech Tip

The Term “Operating System” The term “operating system” is the commonly accepted name for the software that provides the interface between computer hardware and the user and is responsible for the management, coordination, and sharing of limited computer resources such as memory and disk space.

OS Security The operating system itself is the foundation of system security. The operating system does this through the use of a security kernel. The security kernel is also called a reference monitor and is the component of the operating system that enforces the security policies of the operating system. The core of the OS is constructed so that all operations must pass through and be moderated by the security kernel, placing it in complete control over the enforcement of rules. Security kernels must exhibit some properties to be relied upon: they must offer complete mediation, as just discussed, and must be tamperproof and verifiable in operation. Because

they are part of the OS and are in fact a piece of software, ensuring that security kernels are tamperproof and verifiable is a legitimate concern. To achieve assurance with respect to these attributes is a technical matter that is rooted in the actual construction of the OS and technically beyond the level of this book.

Protection Rings Protection rings were devised in the Multics operating system in the 1960s, to deal with security issues associated with time-sharing operations. Protection rings can be enforced by hardware, software, or a combination, and serve to act as a means of managing privilege in a hierarchical manner. Ring 0 is the level with the highest privilege and is the element that acts directly with the physical hardware (CPU and memory). Higher levels, with less privilege, must interact through adjoining rings through specific gates in a predefined manner. Use of rings separates elements such as applications from directly interfacing with the hardware without going through the OS and, specifically, the security kernel.

Host Security Most environments are filled with different operating systems (Windows, Linux, OS X), different versions of those operating systems, and different types of installed applications. Also, today, host-based security for mobile device operating systems is an important security issue, which expands the operating system list to include iOS, Android, and BlackBerry. Each

operating system has security configurations that differ from other systems, and different versions of the same operating system may in fact have variations between them. Ensuring that every computer is “locked down” to the same degree as every other system in the environment can be overwhelming and often results in an unsuccessful and frustrating effort. Host security is important and should always be addressed. Security,

however, should not stop there, as host security is a complementary process to be combined with network security. If individual host computers have vulnerabilities embodied within them, then network security can provide another layer of protection that will, hopefully, stop any intruders who have gotten that far into the environment.

Machine Hardening The key management issue behind running a secure server setup is to identify the specific needs of a server for its proper operation and enable only items necessary for those functions. Keeping all other services and users off the system improves system throughput and increases security. Reducing the attack surface area associated with a server reduces the vulnerabilities now and in the future as updates are required. Once a server has been built and is ready to be placed into operation, the

recording of hash values on all of its crucial files will provide valuable information later in case of a question concerning possible system integrity after a detected intrusion. The use of hash values to detect changes was first developed by Gene Kim and Eugene Spafford at Purdue University in 1992. The concept became the product Tripwire, which is now available in commercial and open source forms. The same basic concept is used by many security packages to detect file-level changes. The primary method of controlling the security impact of a system on a

network is to reduce the available attack surface area. Turning off all services that are not needed or permitted by policy will reduce the number of vulnerabilities. Removing methods of connecting additional devices to a workstation to move data—such as optical drives and USB ports—assists

in controlling the movement of data into and out of the device. User-level controls, such as limiting e-mail attachment options, screening all attachments at the e-mail server level, and reducing network shares to needed shares only, can be used to limit the excessive connectivity that can impact security.

Tech Tip

Server Hardening Tips Specific security needs can vary depending on the server’s specific use, but as a minimum, the following are beneficial:

Remove unnecessary protocols such as Telnet, NetBIOS, Internetwork Packet Exchange (IPX), and File Transfer Protocol (FTP).

Remove unnecessary programs such as Internet Information Services (IIS).

Remove all shares that are not necessary. Rename the administrator account, securing it with a strong password.

Remove the Local Admin account in Windows. Disable unnecessary user accounts.

Disable unnecessary ports and services. Keep the operating system (OS) patched and up to date.

Keep all applications patched and up to date. Turn on event logging for determined security elements.

Control physical access to servers.

Operating System Security and Settings Operating systems are complex programs designed to provide a platform for a wide variety of services to run. Some of these services are extensions of the OS itself, while others are standalone applications that use the OS as a mechanism to connect to other programs and hardware resources. It is up to the OS to manage the security aspects of the hardware being utilized.

Things such as access control mechanisms are great in theory, but it is the practical implementation of these security elements in the OS that provides the actual security profile of a machine.

Tech Tip

Securing a Workstation Workstations are attractive targets for crackers because they are numerous and can serve as entry points into the network and the data that is commonly the target of an attack. Although security is a relative term, following these basic steps will increase workstation security immensely:

Remove unnecessary protocols such as Telnet, NetBIOS, and IPX. Remove unnecessary software.

Remove modems unless needed and authorized. Remove all shares that are not necessary.

Rename the administrator account, securing it with a strong password. Remove the Local Admin account in Windows.

Disable unnecessary user accounts. Disable unnecessary ports and services.

Install an antivirus program and keep abreast of updates. If the floppy drive is not needed, remove or disconnect it.

Consider disabling USB ports via CMOS to restrict data movement to USB devices. If no corporate firewall exists between the machine and the Internet, install a firewall.

Keep the operating system (OS) patched and up to date. Keep all applications patched and up to date.

Turn on event logging for determined security elements.

Early versions of home operating systems did not have separate named accounts for separate users. This was seen as a convenience mechanism; after all, who wants the hassle of signing into the machine? This led to the simple problem that all users could then see and modify and delete

everyone else’s content. Content could be separated by using access control mechanisms, but that required configuration of the OS to manage every user’s identity. Early versions of many OSs came with literally every option turned on. Again, this was a convenience factor, but it led to systems running processes and services that they never used, and increasing the attack surface of the host unnecessarily. Determining the correct settings and implementing them correctly is an

important step in securing a host system. The following sections explore the multitude of controls and options that need to be employed properly to achieve a reasonable level of security on a host system.

OS Hardening You must meet several key requirements to ensure that the system hardening processes described in this section achieve their security goals. These are OS independent and should be a normal part of all system maintenance operations:

Exam Tip: System hardening is the process of preparing and securing a system and involves the removal of all unnecessary software and services.

The base installation of all OS and application software comes from a trusted source, and is verified as correct by using hash values.

Machines are connected only to a completely trusted network during the installation, hardening, and update processes.

The base installation includes all current service packs and updates for both the OS and applications.

Current backup images are taken after hardening and updates to facilitate system restoration to a known state.

These steps ensure that you know what is on the machine, can verify its authenticity, and have an established backup version.

Hardening Microsoft Operating Systems For this book, Windows Vista, Windows 7 and 8, as well as server products Windows Server 2008, 2008 R2, and 2012, are the focus of the discussion. Older Microsoft OSs, such as Windows 3.11, 95, 98, Me, and XP, are no longer supported by Microsoft and won’t be covered in this chapter.

Hardening Windows With the release of Windows Vista, Microsoft tried to make similar security improvements to its mainstream desktop OS as it did to its main server OS, Windows 2003. As a desktop OS, Windows has provided a range of security features for users to secure their systems. Most of these options can be employed via group policies in enterprise setups, making them easily deployable and maintainable across an enterprise. Here are some of the security capabilities introduced with Vista and

continued in later versions of Windows:

User Account Control allows users to operate the system without requiring administrative privileges. If you’ve used Windows Vista and beyond, you’ve undoubtedly seen the “Windows needs your permission to continue” pop-ups. While annoying to many users (one of Apple’s “I’m a Mac” commercials focused specifically on this feature), this feature does help prevent users from “accidentally” making changes to their system configuration. Figure 14.1 shows the User Account Control feature in Windows 7.

• Figure 14.1 Windows 7 User Account Control in action

Windows Firewall includes an outbound filtering capability. Windows allows filtering of traffic coming into and leaving the system, which is useful for controlling things like peer-to-peer applications.

BitLocker allows encryption of all data on a server, including any data volumes. This capability is only available in the higher-end distributions of Windows.

Windows clients work with Network Access Protection. See the discussion of NAP in the following “Hardening Windows Server 2008” section for more details.

Windows Defender is a built-in malware detection and removal tool. Windows Defender detects many types of potentially suspicious software and can prompt the user before allowing applications to make potentially malicious changes.

Tech Tip

Vulnerability Scanning One valuable method for helping administrators secure their systems is vulnerability scanning. Vulnerability scanning is the process of examining your systems and network devices for holes, weaknesses, and issues and finding them before a potential attacker does. Specialized tools called vulnerability scanners are designed to help administrators discover and address vulnerabilities. But there is much more to vulnerability scanning than simply running tools and examining the results—administrators must be able to analyze any discovered vulnerabilities and determine their severity and how to address those vulnerabilities if needed, and if any business processes will be affected by potential fixes. Vulnerability scanning can also help administrators identify common misconfigurations in account setup, patch levels, applications, and operating systems. Most organizations look at vulnerability scanning as an ongoing process, as it is not enough to scan systems once and assume they will be secure from that point on.

Hardening Windows Server 2008 Microsoft touted Windows Server 2008 as its “most secure server” to date upon its release. Building on the changes it made to the Windows Server 2003 and Vista OSs, Microsoft attempted to add more defense-in-depth protections to Windows Server 2008. (Microsoft has a free hardening guide for the Windows Server 2008 OS from its Download Center.) Here are some of the new security capabilities that were introduced in Windows Server 2008:

BitLocker allows encryption of all data on a server, including any data volumes. This capability is also available in certain versions of Vista (and beyond).

Role-based installation of functions and capabilities minimizes the server’s footprint. For example, if a server is going to be a web server, it does not need DNS or SMTP software, and thus those features are no longer installed by default.

Network Access Protection (NAP) controls access to network

resources based on a client computer’s identity and compliance with corporate governance policy. NAP allows network administrators to define granular levels of network access based on client identity, group membership, and the degree to which that client is compliant with corporate policies. NAP can also ensure that clients comply with corporate policies. Suppose, for example, that a sales manager connects her laptop to the corporate network. NAP can be used to examine the laptop and see if it is fully patched and running a company-approved antivirus product with updated signatures. If the laptop does not meet those standards, network access for that laptop can be restricted until the laptop is brought back into compliance with corporate standards.

Read-only domain controllers can be created and deployed in high- risk locations, but they can’t be modified to add new users, change access levels, and so on. This new ability to create and deploy “read- only” domain controllers can be very useful in high-threat environments.

More-granular password policies allow for different password policies on a group or user basis. This allows administrators to assign different password policies and requirements for the sales group and the engineering group if that capability is needed.

Web sites or web applications can be administered within IIS 7. This allows administrators quicker and more convenient administration capabilities, such as the ability to turn on or off specific modules through the IIS management interface. For example, removing CGI support from a web application is a quick and simple operation in IIS 7.

Figure 14.2 lists the initial configuration tasks for Windows 2008.

• Figure 14.2 Windows 2008 Initial Configuration Tasks

Hardening Windows Server 2012 With the release of Windows Server 2012, Microsoft added significant enhancements to its security baseline for its server line:

Replaced the traditional ROM-BIOS with Unified Extensible Firmware Interface (UEFI). Microsoft is using the security-hardened 2.3.1 version, which prevents boot code updates without appropriate digital certificates and signatures.

Extended the trustworthy and verified boot process to the entire Windows OS boot code with a feature known as Secure Boot. UEFI and Secure Boot significantly reduce the risk of malicious code, such as rootkits and boot viruses.

Improved BitLocker functionality to allow administrator-less reboots.

Instituted Early Launch Anti-Malware (ELAM) to ensure that only known, digitally signed antimalware programs can load right after Secure Boot finishes (it does not require UEFI or Secure Boot). This permits legitimate antimalware programs to get into memory and start doing their job before fake antivirus programs or other malicious code can act.

Fully integrated DNSSEC.

Integrated Data Classification with Rights Management Service, so that you can control which users and groups can access which documents based upon content or marked classification.

Included Managed Service Accounts, introduced in Server 2008 R2, to allow for advanced self-maintaining features with extremely long passwords, which automatically reset every 30 days, all under Active Directory control in the enterprise.

Windows 2012 R2 continued the security feature set through

refinements and improvements across many of the security features. Consistent with Microsoft’s claim that Windows Server 2008 was its most secure server to date at the time of release, its subsequent track record shows that the company is committed to unrivaled security in enterprise server products. The tools available in each subsequent release of the server OS are designed to increase the difficulty factor for attackers, eliminating known methods of exploitation. The challenge is in administrating the security functions, although the integration of many of these via Active Directory makes this much more manageable than in the past.

Microsoft Security Compliance Manager Microsoft provides a tool, Security Compliance Manager (SCM), to assist system and enterprise administrators with the configuration of security options across a wide range of Microsoft platforms. SCM allows administrators to use group policy objects (GPOs) to deploy security configurations across Internet Explorer, the desktop OSs, server OSs, and common applications such as Microsoft Office. Figure 14.3 illustrates some of the menu options available in SCM, currently version 3.0.

• Figure 14.3 Microsoft Security Compliance Manager

Microsoft Attack Surface Analyzer One of the challenges in a modern enterprise is understanding the impact of system changes from the installation or upgrade of an application on a system. To help you overcome that challenge, Microsoft has released the Attack Surface Analyzer (ASA), a free tool that can be deployed on a system before a change and again after a change to analyze the changes to various system properties as a result of the change. Using ASA, developers can view changes in the attack surface resulting

from the introduction of their code onto the Windows platform, and system administrators can assess the aggregate attack surface change by the installation of an application. Security auditors can use the tool to evaluate the risk of a particular piece of software installed on the Windows platform. And if ASA is deployed in a baseline mode before an incident, security incident responders can potentially use ASA to gain a better understanding of the state of a system’s security during an investigation.

Hardening UNIX- or Linux-based Operating Systems While you do not have the advantage of a single manufacturer for all UNIX operating systems (like you do with Windows operating systems), the concepts behind securing different UNIX- or Linux-based operating systems are similar whether the manufacturer is Red Hat or Sun Microsystems. Indeed, the overall tasks involved with hardening all operating systems are remarkably similar.

Establishing General UNIX Baselines General UNIX baselining follows similar concepts as baselining for Windows OSs: disable unnecessary services, restrict permissions on files

and directories, remove unnecessary software, apply patches, remove unnecessary users, and apply password guidelines. Some versions of UNIX provide GUI-based tools for these tasks, while others require administrators to edit configuration files manually. In most cases, anything that can be accomplished through a GUI can be accomplished from the command line or by manually editing configuration files. Like Windows systems, UNIX systems are easiest to secure and

baseline if they are providing a single service or performing a single function, such as acting as a Simple Mail Transfer Protocol (SMTP) server or web server. Prior to performing any software installations or baselining, the administrator should define the purpose of the system and identify all required capabilities and functions. One nice advantage of UNIX systems is that you typically have complete control over what does or does not get installed on the system. During the installation process, the administrator can select which services and applications are placed on the system, offering an opportunity to not install services and applications that will not be required. However, this assumes that the administrator knows and understands the purpose of this system, which is not always the case. In other cases, the function of the system itself may have changed.

Tech Tip

Runlevels Runlevels are used to describe the state of init (initialization) and what system services are operating in UNIX systems. For example, runlevel 0 is shutdown. Runlevel 1 is single-user mode (typically for administrative purposes). Runlevels 2 through 5 are user defined (that is, administrators can define what services are running at each level). Runlevel 6 is for reboot.

Regardless of the installation decisions, the administrator may need to remove applications or components that are no longer needed. With UNIX systems, no “add/remove program” wizard is usually available, unlike Windows, but you will often encounter package managers that help you remove unneeded components and applications automatically. On some

UNIX versions, though, you must manually delete the files associated with the applications or services you want to remove. Services on a UNIX system (called daemons) can be controlled through

a number of different mechanisms. As the root user, an administrator can start and stop services manually from the command line or through a GUI tool. The OS can also stop and start services automatically through configuration files (usually contained in the /etc directory). (Note that UNIX systems vary a good deal in this regard, as some use a super-server process, such as inetd, while others have individual configuration files for each network service.) Unlike Windows, UNIX systems can also have different runlevels, in which the system can be configured to bring up different services depending on the runlevel selected. On a running UNIX system, you can see which processes, applications,

and services are running by using the process status, or ps, command, as shown in Figure 14.3. To stop a running service, an administrator can identify the service by its unique process identifier (PID) and then use the kill command to stop the service. For example, if you wanted to stop the bluetooth-applet service in Figure 14.4, you would use the command kill 2443. To prevent this service from starting again when the system is rebooted, you would have to modify the appropriate runlevels to remove this service, as shown in Figure 14.5, or modify the configuration files that control this service.

• Figure 14.4 ps command run on a Fedora system

• Figure 14.5 Service Configuration utility from a Fedora system

Accounts on a UNIX system can also be controlled via GUIs in some cases and command-line interfaces in others. On most popular UNIX versions, the user information can be found in the passwd file located in the /etc directory. By manually editing this file, you can add, delete, or modify user accounts on the system. By examining this file, an administrator can see which user accounts exist on the system and then

determine which accounts to remove or disable. On most UNIX systems, if you remove the user account from the passwd file, you must manually remove any files that belong to that user, including home directories. Most modern UNIX versions store the actual password associated with a user account in a shadow file located in the /etc directory. The shadow file contains the actual password hashes for each user account and is readable only by the root user (or a process with root-level permissions). How you patch a UNIX system depends a great deal on the UNIX

version in use and the patch being applied. In some cases, a patch will consist of a series of manual steps requiring the administrator to replace files, change permissions, and alter directories. In other cases, the patches are executable scripts or utilities that perform the patch actions automatically. Some UNIX versions, such as Red Hat and Solaris, have built-in utilities that handle the patching process. In those cases, the administrator downloads a specifically formatted file that the patching utility then processes to perform any modifications or updates that need to be made. To better illustrate UNIX baselines, we will examine two popular

UNIX-based operating systems: Solaris and Red Hat Linux.

Tech Tip

TCP Wrappers TCP wrappers can be a great additional layer of protection for UNIX systems. When creating a security baseline for UNIX systems, be sure to consider the use of TCP wrappers.

Another method of examining a system for vulnerabilities is done through observation— monitoring network traffic from specific systems, for example. This is called passive vulnerability scanning as administrators are merely observing what the system does and how it behaves. For instance, if an administrator sees FTP traffic traveling to a dedicated mail server, then they know they need to examine and possibly disable that FTP service.

Pluggable Authentication Modules (PAM) are a mechanism for providing interoperation and secure access to a variety of services on different platforms. They provide a common authentication scheme that can be used with a wide variety of applications. PAM has an extensive documentation set with details about both using PAM and writing modules to integrate PAM with applications.

Hardening Linux Linux is a rather unique operating system. It is UNIX-based, very powerful, open source, can be obtained for free, and is available in many different “versions” or distributions (“distros”) from several vendors. Linux was initially conceived and written by Linus Torvalds in 1991. His concept of creating a lightweight, flexible, and free operating system gave rise to an entirely new operating system that is very popular and is installed on millions of computers around the world. Due to its open nature, the entire source-code base for the operating system is available to anyone who wants to examine it, modify it, or recompile it for their own specific uses. Linux is a favored operating system among many security professionals, system administrators, and other highly technical users who enjoy the flexibility and power that Linux provides.

Many Linux distributions are “open source,” meaning if you have the time, energy, and expertise, you can access and modify the code that comprises the operating system itself.

While most versions of Linux can be obtained for free simply by downloading them from the Internet (including major commercial distributions), you can also purchase commercial versions of the Linux operating system from vendors, such as Red Hat, Slackware, SuSE, and Debian, who have built a business out of providing custom versions of Linux along with support and training. We will use Fedora, a popular (and

free) Linux distribution, as the example for the rest of this section. Regardless of which Linux version you prefer, baselining a Linux system follows the same guidelines as any other UNIX system: disable unnecessary services, restrict permissions on files and directories, remove unnecessary software, apply patches, remove unnecessary users, and apply password guidelines. Services under Linux are normally controlled by their own

configuration files or by xinetd, the extended Internet services daemon. Instead of starting all Internet services, such as FTP servers, at system startup, some Linux distributions use xinetd to listen for incoming connections. Xinetd listens to all the appropriate ports (those that match the services in its configuration files), and when a connection request comes in, xinetd starts the appropriate server and hands over the connection request. This “master process” approach makes it fairly simple to disable unwanted services—all the configuration information for each server is located in /etc/xinetd.d, with a configuration file for each process. Permissions under Linux are the same as for other UNIX-based

operating systems. There are permissions for owner, group, and others (or world). Permissions are based on the same read-write-execute principle and can be adjusted using the chmod command. Individual and group ownership information can be changed using chown and chgrp, respectively. As with other baselining exercises, permissions should be as restrictive as functionally possible, giving read-only access when possible and write or execute access when necessary.

Tech Tip

Linux Variants The original Linux code is open source, and from this code many diverse variants have been developed. While these are all very similar, there are difference in how developers approached some activities such as patching and source code repositories. The different distros of Linux and methods of applying them are related to the lineage of the Linux distro itself. For distros that derive from the Debian line (Debian, Ubuntu, Linux Mint) the file format .deb is used. For distros derived from Redhat (Redhat, RHEL, Fedora, CentOS, SUSE)

the .rpm file structure is used. The two formats, .deb and .rpm, are basically archive files with metadata to assist

installers. The differences are noticeable when a user uses tools to apply the updates. The underlying tool for .deb is dpkg, and rpm for .rpm. But these are simple tools, not repository managers; for repository management and better functionality, apt-get is used with .deb and yum is used with rpm. Although each of these options is different in usage and each has its champions, at the end of the day, both paths provide the same services for administrators. The key takeaway is although similar, there are differences in versions of Linux that make administration less universal in process.

Adding and removing software under Linux is typically done through a package manager. In Fedora Core Linux, the package manager is called Red Hat Package Manager, or rpm for short. Using rpm, you can add, modify, update, or remove software packages from your system. Using the rpm –qa command will give you a list of all the software packages installed on your Red Hat system. You can remove any packages you do not wish to leave installed by using the rpm -e command. As with most things under Linux, there is a GUI-based utility to accomplish this same task. The GUI-based Add/Remove Software utility is shown in Figure 14.6.

• Figure 14.6 Fedora Add/Remove Software utility

Patching and keeping a Fedora Linux system up to date is a fairly simple exercise, as well. Fedora has provided an Update Agent that, once configured, will examine your system, obtain the list of available updates, and, if desired, install those updates on your system. Like any other operating system, it is important to maintain the patch level of your Fedora system. For more information on the Fedora Update Agent, see the “Updates (a.k.a. Hotfixes, Service Packs, and Patches)” section later in this chapter. Managing and maintaining user accounts under Linux can be

accomplished with either the command line or a GUI. Unlike certain other

operating systems, there’s really only one default account for Linux systems—the root, or superuser, account. The root account has complete and total control over the system and should therefore be protected with an exceptionally strong password. Many administrators will configure their systems to prevent anyone from logging in directly as root; instead they must log in with their own personal accounts and switch to the root account using the su command. Adding user accounts can be done with the useradd command, and unwanted user accounts can be removed using the userdel command. Additionally you can manually edit /etc/passwd to add or remove user accounts. User accounts can also be managed via a GUI, as shown in Figure 14.7.

• Figure 14.7 Fedora User Manager

For increased local security, Fedora also provides a built-in firewall function that can be managed either via the command line or through a GUI, as shown in Figure 14.8. To protect network access to the local system, administrators can control which ports external users may connect to, such as mail, FTP, or web. Administrators may choose a security level, from high, medium, off, or a customized option that enables them to individually select which ports on which interfaces external users may connect to.

• Figure 14.8 Fedora Firewall Configuration GUI

In addition to the built-in firewall functions, administrators may also use TCP wrappers like those discussed earlier in this chapter. By specifying

host and port combinations in /etc/hosts. allow, administrators can allow certain hosts to connect on certain ports. The firewall function and hosts.allow must work together if both functions are used on the same system. The connection must be allowed by both utilities or it will be dropped.

Hardening Mac OS X Apple’s operating system is essentially a new variant of the UNIX operating system. While this POSIX-compliant OS brings a new level of power, flexibility, and stability to Mac users everywhere, it also brings a new level of security concerns. Traditionally, the Mac operating system was largely ignored by the hacker community—the deployment was relatively small and largely restricted to individual users or departments. With the migration to a UNIX-based OS and a rise in the number of Macs on the market, Mac users should anticipate a sharp increase in unwanted attention and scrutiny from potential attackers. Because it is a UNIX-based OS, the same rough guidelines for all UNIX

systems apply to Mac OS X. Apple has included some security-specific features to help protect its user base:

Mandatory access controls for access to system resources Only processes that are explicitly granted access are allowed to access system resources such as networking, file systems, process execution, and so on.

Tagged downloads Any file downloaded with Safari, iChat, or Mail is automatically tagged with metadata, including the source URL, date and time of download, and so on. If the download was an archive (such as a zip file), the same metadata is tagged to any file extracted from the archive. Users are prompted with this information the first time they try to run or open the downloaded file.

Execute disable Leopard (OS X 10.5) and beyond provides no- execute stack protection. Essentially this means that certain portions of

the stack have been marked as “data only” and the OS will not execute any instructions in regions marked as data only. This helps protect against buffer-overflow attacks.

Library randomization In another attempt to help defeat buffer- overflow attacks, Leopard (OS X 10.5) and beyond loads system libraries into random locations, making it harder for attackers to reference static system library locations in their exploit code.

FileVault FileVault encrypts files with AES encryption. When this feature is enabled, everything in the user’s home directory is automatically encrypted.

Application-aware firewall The Apple Application firewall allows users to restrict network access on both a per-application and a per- port basis.

Pre-emptive multitasking and memory protection These features provide a means for the system to ensure that multiple applications can be run simultaneously without interrupting or corrupting each other.

Gatekeeper The Gatekeeper application is employed to make it safer to download and deploy applications. The combination of the Gatekeeper application and the control Apple exerts over applications in its App store provides one of the safest sets of software distribution.

App Sandbox The App Sandbox in OS X provides a means of ensuring that apps are separated from the OS in ways to protect critical components from malicious software.

File permissions in OS X are nearly identical to those in any other UNIX variant and are based on separate read, write, and execute permissions for owner, group, and world. While these permissions can be adjusted manually from a command-line interface, with the standard chown, chmod, and chgrp commands, Apple again provides some nice interface capabilities for viewing and managing file and directory permissions. By selecting the properties of any given file or folder, the

user can view and modify the permissions for that file or folder, as shown in Figure 14.9. Note that the GUI follows the same user-group-world pattern of permissions that other UNIX variants follow, though Apple uses the term others as opposed to world.

• Figure 14.9 Setting file permissions in Mac OS X

This GUI allows users to restrict access to sensitive files and directories quickly and effectively. By default, OS X limits a user’s ability to access or modify certain areas of the file system, including those areas containing system binaries. However, these restrictions can be circumvented by a user with the appropriate permissions or by certain third-party applications. Removing unwanted or unnecessary programs in OS X is usually done

through the program’s own uninstaller utility or by simply using the Finder to locate and then delete the folder containing the program and associated utilities. Like Windows, OS X maps certain file extensions to specific programs, so deleting a program that handles specific extension types may require that an administrator clear up associated extensions.

Like most UNIX-based OSs, OS X is a multiuser platform. As part of the baselining effort, the active user accounts should be examined to ensure they have the right level of access, permissions, group memberships, and so on. Mac OS X also permits administrators to lock accounts so that they can be modified only by users with administrative- level privileges.

There are three types of accounts in OS X: User, Administrator, and Root. User is the account with the lowest privileges, and typical “users” should be given this type of account. Administrator accounts have “root-like” permissions except they cannot add, modify, or delete files in the system domain. The Root account is essentially the same as the root account on any UNIX system; however, OS X disables the Root account by default. You must enable the Root account if you want to use it on a Mac.

Updates (a.k.a. Hotfixes, Service Packs, and Patches) Operating systems are large and complex mixes of interrelated software modules written by dozens or even thousands of separate individuals. With the push toward GUI-based functionality and enhanced capabilities that has occurred over the past several years, operating systems have continued to grow and expand. Windows Vista contains approximately 50 million lines of code, and though it may be one of the largest in that respect, other modern operating systems are not far behind. As operating systems continue to grow and introduce new functions, the potential for problems with the code grows as well. It is almost impossible for an operating system vendor to test its product on every possible platform under every possible circumstance, so functionality and security issues do arise after an operating system has been released. To the average user or system administrator, this means a fairly constant stream of updates designed to correct problems, replace sections of code, or even add new features to an installed operating system.

Vendors typically follow a hierarchy for software updates:

Hotfix This is a term given to a (usually) small software update designed to address a specific problem, such as a buffer overflow in an application that exposes the system to attacks. Hotfixes are typically developed in reaction to a discovered problem and are produced and then released rather quickly. Hotfixes typically address critical, security-related issues and should be applied to the affected application or operating system as soon as possible.

Patch This term is usually applied to a more formal, larger software update that may address several or many software problems. Patches often contain enhancements or additional capabilities as well as fixes for known bugs. Patches are usually developed over a longer period of time.

Service pack This term is usually given to a large collection of patches and hotfixes rolled into a single, rather large package. Service packs are designed to bring a system up to the latest known good level all at once, rather than requiring the user or system administrator to download dozens or hundreds of updates separately.

Every operating system, from Linux to Solaris to Windows, requires software updates, and each operating system has different methods of assisting users in keeping their systems up to date. Microsoft, for example, typically makes updates available for download from its web site. While most administrators or technically proficient users may prefer to identify and download updates individually, Microsoft recognizes that nontechnical users prefer a simpler approach, which Microsoft has built into its operating systems. Beginning with Windows Vista, and Server 2003, Microsoft provides an automated update functionality that will, once configured, locate any required updates, download them to your system, and even install the updates if that is your preference. Figure 14.10 shows the Automatic Updates window, which can be found in the Control Panel. Note that both the web-based updates and Automatic Updates require

active Internet connections to retrieve information and updates from Microsoft.

• Figure 14.10 Automatic Updates settings in Windows 7

The Windows Update utility (see Figure 14.11) can perform an on- demand search for updates or be configured to scan for, download, and even install updates automatically—essentially the same functions as Automatic Updates with a new look. An especially nice feature of Windows Update is the ability to scan for and download patches for other Microsoft software, such as Office, as well as updates and patches for the operating system itself.

• Figure 14.11 Windows Update utility in Windows 7

Microsoft is not alone in providing utilities to assist users in keeping their systems up to date and secure. Fedora Linux contains a utility called the Package Updater, shown in Figure 14.12, which does essentially the same thing. Running the utility will show you which updates are available and allow you to select which updates to download and apply. As with most operating systems, you can configure Fedora to automatically download and apply available updates.

• Figure 14.12 Fedora software package update utility

Regardless of the method you use to update the operating system, it is critically important to keep systems up to date. New security advisories come out every day, and while a buffer overflow may be a “potential” problem today, it will almost certainly become a “definite” problem in the near future. Much like the steps taken to baseline and initially secure an operating system, keeping every system patched and up to date is critical to protecting the system and the information it contains.

Exam Tip: All software will require changes/patches over time. Managing patches is an essential element of a security program.

Operating System Patching Every OS, from Linux to Windows, requires software updates, and each OS has different methods of assisting users in keeping their systems up to date. Microsoft, for example, typically makes updates available for download from its web site. While most administrators or technically proficient users may prefer to identify and download updates individually, Microsoft recognizes that nontechnical users prefer a simpler approach, which Microsoft has built into its operating systems. In Windows 7 and 8 and Windows Server 2012, Microsoft provides an automated update functionality that will, once configured, locate any required updates, download them to your system, and even install the updates if that is your preference. In Microsoft Windows, the Windows Update utility (see Figure 14.11) can perform an on-demand search for updates or be configured to scan for, download, and even install updates automatically— essentially the same functions as Automatic Updates with a new look. An especially nice feature of Windows Update is the ability to scan for and download patches for other Microsoft software, such as Office, as well as

updates and patches for the OS itself.

Tech Tip

Windows Updates of the Future Microsoft has announced that beginning with Windows 10 it will discontinue the monthly patch distribution process referred to as Patch Tuesday. The new method will be continuous, seamless updates in the background. This has raised questions in enterprises as to how they can test updates before applying them in production.

How you patch a Linux system depends a great deal on the specific version in use and the patch being applied. In some cases, a patch will consist of a series of manual steps requiring the administrator to replace files, change permissions, and alter directories. In other cases, the patches are executable scripts or utilities that perform the patch actions automatically. Some Linux versions, such as Red Hat, have built-in utilities that handle the patching process. In those cases, the administrator downloads a specifically formatted file that the patching utility then processes to perform any modifications or updates that need to be made. Regardless of the method you use to update the OS, it is critically

important to keep systems up to date. New security advisories come out every day, and while a buffer overflow may be a “potential” problem today, it will almost certainly become a “definite” problem in the near future. Much like the steps taken to baseline and initially secure an OS, keeping every system patched and up to date is critical to protecting the system and the information it contains.

Application Updates Just as operating systems need patches, so do applications. Managing the wide variety of applications and the required updates from numerous different software vendors can be a daunting challenge. This has created a niche market for patch-management software. In most enterprises, some

form of automated patch management solution is used, both to reduce labor and to ensure updates are applied appropriately across the enterprise.

Antimalware In the early days of PC use, threats were limited: most home users were not connected to the Internet 24/7 through broadband connections, and the most common threat was a virus passed from computer to computer via an infected floppy disk (much like the medical definition, a computer virus is something that can infect the host and replicate itself). But things have changed dramatically since those early days, and current threats pose a much greater risk than ever before. According to SANS Internet Storm Center, the average survival time of an unpatched Windows PC on the Internet is less than 60 minutes (http://isc.sans.org/survivaltime.html). This is the estimated time before an automated probe finds the system, penetrates it, and compromises it. Automated probes from botnets and worms are not the only threats roaming the Internet—there are viruses and malware spread by e-mail, phishing, infected web sites that execute code on your system when you visit them, adware, spyware, and so on. Fortunately, as the threats increase in complexity and capability, so do the products designed to stop them.

Cross Check Malware Malware comes in many forms and is covered specifically in Chapter 15. Antivirus solutions and proper workstation configurations are part of a defensive posture against various forms of malware. Additional steps include policy and procedure actions, prohibiting file sharing via USB or external media, and prohibiting access to certain web sites.

Antivirus Antivirus (AV) products attempt to identify, neutralize, or remove malicious programs, macros, and files. These products were initially

designed to detect and remove computer viruses, though many of the antivirus products are now bundled with additional security products and features. Although antivirus products have had over two decades to refine their

capabilities, the purpose of the antivirus products remains the same: to detect and eliminate computer viruses and malware. Most antivirus products combine the following approaches when scanning for viruses:

Signature-based scanning Much like an intrusion detection system (IDS), the antivirus products scan programs, files, macros, e-mails, and other data for known worms, viruses, and malware. The antivirus product contains a virus dictionary with thousands of known virus signatures that must be frequently updated, as new viruses are discovered daily. This approach will catch known viruses but is limited by the virus dictionary—what it does not know about it cannot catch.

Heuristic scanning (or analysis) Heuristic scanning does not rely on a virus dictionary. Instead, it looks for suspicious behavior—anything that does not fit into a “normal” pattern of behavior for the OS and applications running on the system being protected.

Most current antivirus software packages provide protection against a wide range of threats, including viruses, worms, Trojans, and other malware. Use of an up-to-date antivirus package is essential in the current threat environment.

Exam Tip: Heuristic scanning is a method of detecting potentially malicious or “virus-like” behavior by examining what a program or section of code does. Anything that is “suspicious” or potentially “malicious” is closely examined to determine whether or not it is a threat to the system. Using heuristic scanning, an antivirus product attempts to identify new viruses or heavily

modified versions of existing viruses before they can damage your system.

As signature-based scanning is a familiar concept, let’s examine heuristic scanning in more detail. Heuristic scanning typically looks for commands or instructions that are not normally found in application programs, such as attempts to access a reserved memory register. Most antivirus products use either a weight-based system or a rule-based system in their heuristic scanning (more effective products use a combination of both techniques). A weight-based system rates every suspicious behavior based on the degree of threat associated with that behavior. If the set threshold is passed based on a single behavior or a combination of behaviors, the antivirus product will treat the process, application, macro, and so on that is performing the behavior(s) as a threat to the system. A rule-based system compares activity to a set of rules meant to detect and identify malicious software. If part of the software matches a rule, or if a process, application, macro, and so on performs a behavior that matches a rule, the antivirus software will treat that as a threat to the local system. Some heuristic products are very advanced and contain capabilities for

examining memory usage and addressing, a parser for examining executable code, a logic flow analyzer, and a disassembler/emulator so they can “guess” what the code is designed to do and whether or not it is malicious.

Computer virus writers’ intentions have changed over the years, from simply spreading a virus and wanting to be noticed, to today’s stealthy botnet-creating criminals. One method of remaining hidden is to produce viruses that can morph to lower their detection rates by standard antivirus programs. The number of variants for some viruses has increased from less than 10 to greater than 10,000. This explosion in signatures has created two issues. One, users must constantly (sometimes more than daily) update their signature file. And, more importantly, detection methods are having to change as the number of signatures become too large to scan quickly. For end users, the bottom line is simple: update signatures automatically, and at least daily.

As with IDS/IPS products, encryption and obfuscation pose a problem

for antivirus products: anything that cannot be read cannot be matched against current virus dictionaries or activity patterns. To combat the use of encryption in malware and viruses, many heuristic scanners look for encryption and decryption loops. As malware is usually designed to run alone and unattended, if it uses encryption, it must contain all the instructions to encrypt and decrypt itself as needed. Heuristic scanners look for instructions such as the initialization of a pointer with a valid memory address, manipulation of a counter, or a branch condition based on a counter value. While these actions don’t always indicate the presence of an encryption/decryption loop, if the heuristic engine can find a loop, it might be able to decrypt the software in a protected memory space, such as an emulator, and evaluate the software in more detail. Many viruses share common encryption/decryption routines that help antivirus developers. Current antivirus products are highly configurable and most offerings

will have the following capabilities:

Automated updates Perhaps the most important feature of a good antivirus solution is its ability to keep itself up to date by automatically downloading the latest virus signatures on a frequent basis. This usually requires that the system be connected to the Internet in some fashion and that updates be performed on a daily (or more frequent) basis.

Automated scanning Most antivirus products allow for the scheduling of automated scans so that you can designate when the antivirus product will examine the local system for infected files. These automated scans can typically be scheduled for specific days and times, and the scanning parameters can be configured to specify what drives, directories, and types of files are scanned.

Media scanning Removable media is still a common method for virus and malware propagation, and most antivirus products can be configured to automatically scan optical media, USB drives, memory sticks, or any other type of removable media as soon as they are connected to or accessed by the local system.

Manual scanning Many antivirus products allow the user to scan drives, files, or directories (folders) “on demand.”

E-mail scanning E-mail is still a major method of virus and malware propagation. Many antivirus products give users the ability to scan both incoming and outgoing messages as well as any attachments.

Resolution When the antivirus product detects an infected file or application, it can typically perform one of several actions. The antivirus product may quarantine the file, making it inaccessible; it may try to repair the file by removing the infection or offending code; or it may delete the infected file. Most antivirus products allow the user to specify the desired action, and some allow for an escalation in actions such as cleaning the infected file if possible and quarantining the file if it cannot be cleaned.

Antivirus solutions are typically installed on individual systems (desktops, servers, and even mobile devices), but network-based antivirus capabilities are also available in many commercial gateway products. These gateway products often combine firewall, IDS/IPS, and antivirus capabilities into a single integrated platform. Most organizations will also employ antivirus solutions on e-mail servers, as that continues to be a very popular propagation method for viruses. While the installation of a good antivirus product is still considered a

necessary best practice, there is growing concern about the effectiveness of antivirus products against developing threats. Early viruses often exhibited destructive behaviors; were poorly written, modified files; and were less concerned with hiding their presence than they were with propagation. We are seeing an emergence of viruses and malware created by professionals, sometimes financed by criminal organizations or governments, which go to great lengths to hide their presence. These viruses and malware are often used to steal sensitive information or turn the infected PC into part of a larger botnet for use in spamming or attack operations.

Exam Tip: Antivirus is an essential security application on all platforms. There are compliance schemes that mandate antivirus deployment, such as PCI DSS and NERC CIP.

Antivirus Software for Servers The need for antivirus protection on servers depends a great deal on the use of the server. Some types of servers, such as e-mail servers, require extensive antivirus protection because of the services they provide. Other servers (domain controllers and remote access servers, for example) may not require any antivirus software, as they do not allow users to place files on them. File servers need protection, as do certain types of application servers. There is no general rule, so each server and its role in the network will need to be examined to determine whether it needs antivirus software.

Antivirus Software for Workstations Antivirus packages are available from a wide range of vendors. Running a network of computers without this basic level of protection will be an exercise in futility. Even though the number of widespread, indiscriminate broadcast virus attacks has decreased because of the effectiveness of antivirus software, it is still necessary to use antivirus software; the time and money you would spend cleaning up after a virus attack more than equals the cost of antivirus protection. The majority of viruses today exist to create zombie machines for botnets that enable others to control resources on your PC. Even more important, once connected by networks, computers can spread a virus from machine to machine with an ease that’s even greater than simple USB flash drive transfer. One unprotected machine can lead to problems throughout a network as other machines have to use their antivirus software to attempt to clean up a spreading infection. Apple Mac computers were once considered by many users to be

immune because very few examples of malicious software targeting Macs

existed. This was not due to anything other than a low market share, and hence the devices were ignored by the malware community as a whole. As Mac has increased in market share, so has its exposure, and today a variety of Mac OS X malware steals files and passwords and is even used to take users’ pictures with the computer’s built-in webcam. All user machines need to install antivirus software in today’s environment, because any computer can become a target.

Antispam If you have an e-mail account, you’ve likely received spam, that endless stream of unsolicited, electronic junk mail advertising get-rich-quick schemes, asking you to validate your bank account’s password, or inviting you to visit one web site or another. Despite federal legislation (such as the CAN-SPAM Act of 2003) and promises from IT industry giants like Bill Gates (“Two years from now, spam will be solved”—2004), spam is alive and well and filling up your inbox as you read this. Industry experts have been fighting the spam battle for years, and while significant progress has been made in the development of antispam products, unfortunately the spammers have proven to be very creative and very dedicated in their quest to fill your inbox.

Spam is not a new problem. It’s reported that the first spam message was sent on May 1, 1978 by a Digital Equipment Corporation sales representative. This sales representative attempted to send a message to all ARPANET users on the West Coast.

Antispam products attempt to filter out that endless stream of junk e- mail so you don’t have to. Some antispam products operate at the corporate level, filtering messages as they enter or leave designated mail servers. Other products operate at the host level, filtering messages as they come into your personal inbox. Most antispam products use similar techniques and approaches for filtering out spam:

Black listing Several organizations maintain lists of servers or domains that generate or have generated spam. Most gateway- or server-level products can reference these black lists and automatically reject any mail coming from servers or domains on the black lists.

Header filtering The antispam products look at the message headers to see if they are forged. E-mail headers typically contain information such as sender, receiver, servers used to transmit the message, and so on. Spammers often forge information in message headers in an attempt to hide where the message is really coming from.

Content filtering The content of the message is examined for certain key words or phrases that are common to spam but rarely seen in legitimate e-mails (“get rich now” for example). Unfortunately, content filtering does occasionally flag legitimate messages as spam.

Language filtering Some spam products allow you to filter out e- mails written in certain languages.

User-defined filtering Most antispam products allow end users to develop their own filters, such as always allowing e-mail from a specific source even if it would normally be blocked by a content filter.

Trapping Some products will monitor unpublished e-mail addresses for incoming spam—anything sent to an unpublished and otherwise unused account is likely to be spam.

Enforcing the specifications of the protocol Some spam-generation tools don’t properly follow the SMTP protocol. By enforcing the technical requirements of SMTP, some spam can be rejected as delivery is attempted.

Egress filtering This technique scans mail as it leaves an organization to catch spam before it is sent to other organizations.

Cross Check Spam The topic of spam and all the interesting details of undesired e-mail is presented in Chapter 16. Spam is listed here as it is considered a client threat, but the main methods of combating spam are covered in Chapter 16.

Antispyware Most antivirus products will include antispyware capabilities as well. While antivirus programs were designed to watch for the writing of files to the file system, many current forms of malware avoid the file system to avoid this form of detection. Newer antivirus products are adapting and scanning memory as well as watching file system access in an attempt to detect advanced malware. Spyware is the term used to define malware that is designed to steal information from the system, such as keystrokes, passwords, PINs, and keys. Antispyware helps protect your systems from the ever-increasing flood of malware that seeks to watch your keystrokes, steal your passwords, and report sensitive information back to attackers. Many of these attack vectors work in system memory to avoid easy detection.

Windows Defender As part of its ongoing efforts to help secure its PC operating systems, Microsoft released a free utility called Windows Defender in February 2006. The stated purpose of Windows Defender is to protect your computer from spyware and other unwanted software (http://windows.microsoft.com/en-us/windows/using- defender#1TC=windows-7). Windows Defender is standard with all versions of the Vista and Windows 7 operating systems and is available via free download in both 32- and 64-bit versions. It has the following capabilities:

Spyware detection and removal Windows Defender is designed to find and remove spyware and other unwanted programs that display pop-ups, modify browser or Internet settings, or steal personal information from your PC.

Scheduled scanning You can schedule when you want your system to be scanned or you can run scans on demand.

Automatic updates Updates to the product can be automatically downloaded and installed without user interaction.

Real-time protection Processes are monitored in real time to stop spyware and malware when they first launch, attempt to install themselves, or attempt to access your PC.

Software Explorer One of the more interesting capabilities within Windows Defender is the ability to examine the various programs running on your computer. Windows Defender allows you to look at programs that run automatically on startup, are currently running on your PC, or are accessing network connections on your PC. Windows Defender provides you with details such as the publisher of the software, when it was installed on your PC, whether or not the software is “good” or considered to be known malware, the file size, publication date, and other information.

Configurable responses Windows Defender lets you choose what actions you want to take in response to detected threats (see Figure 14.13); you can automatically disable the software, quarantine it, attempt to uninstall it, and perform other tasks.

• Figure 14.13 Windows Defender configuration options

Pop-up Blockers One of the most annoying nuisances associated with web browsing is the pop-up ad. Pop-up ads are online advertisements designed to attract web traffic to specific web sites, capture e-mail addresses, advertise a product, and perform other tasks. If you’ve spent more than an hour surfing the Web, you’ve undoubtedly seen them. They’re created when the web site you are visiting opens a new web browser window for the sole purpose of displaying an advertisement. Pop-up ads typically appear in front of your current browser window to catch your attention (and disrupt your browsing). Pop-up ads can range from mildly annoying, generating one or two pop-ups, to system crippling if a malicious web site attempts to open thousands of pop-up windows on your system. Similar to the pop-up ad is the pop-under ad that opens up behind your

current browser window. You won’t see these ads until your current window is closed, and they are considered by some to be less annoying than pop-ups. Another form of pop-up is the hover ad that uses Dynamic HTML to appear as a floating window superimposed over your browser window. To some users, pop-up ads are as undesirable as spam, and many web browsers now allow users to restrict or prevent pop-ups with functionality either built into the web browser or available as an add-on. Internet Explorer contains a built-in Pop-up Blocker (shown in Figure 14.14 and available from the Tools menu in Internet Explorer 11).

• Figure 14.14 Pop-up Blocker in IE 11

Firefox also contains a built-in pop-up blocker (available by choosing

Tools | Options and then selecting the Content tab). Popular add-ons such as the Google and Yahoo! toolbars also contain pop-up blockers. If these freely available options are not enough for your needs, many commercial security suites from McAfee, Symantec, and Check Point contain pop-up blocking capabilities as well. Users must be careful when selecting a pop- up blocker, as some unscrupulous developers have created adware products disguised as free pop-up blockers or other security tools.

Exam Tip: Pop-up blockers are used to prevent web sites from opening additional web browser windows or tabs without specific user consent.

Pop-ups ads can be generated in a number of ways, including JavaScript and Adobe Flash, and an effective pop-up blocker must be able to deal with the many methods used to create pop-ups. When a pop-up is created, users typically can click a close or cancel button inside the pop-up or close the new window using a method available through the OS, such as closing the window from the taskbar in Windows. With the advanced features available to them in a web development environment, some unscrupulous developers program the close or cancel button in their pop-ups to launch new pop-ups, redirect the user, run commands on the local system, or even load software. Pop-ups should not be confused with adware. Pop-ups are ads that

appear as you visit web pages. Adware is advertising-supported software. Adware automatically downloads and displays ads on your computer after the adware has been installed, and these ads are typically shown while the software is being used. Adware is often touted as “free” software, as the user pays nothing for the software but must agree to allow ads to be downloaded and displayed before using the software. This approach is very popular on smartphones and mobile devices.

White Listing vs. Black Listing Applications Applications can be controlled at the OS at the time of start via black listing or white listing. Black listing is essentially noting which applications should not be allowed to run on the machine. This is basically a permanent “ignore” or “call block” type capability. White listing is the exact opposite: it consists of a list of allowed applications. Each of these approaches has advantages and disadvantages. Black listing is difficult to use against dynamic threats, as the identification of a specific application can easily be avoided through minor changes. White listing is easier to employ from the aspect of the identification of applications that are allowed to run—hash values can be used to ensure the executables are not corrupted. The challenge in white listing is the number of potential applications that are run on a typical machine. For a single-purpose machine, such as a database server, white listing can be relatively easy to employ. For multipurpose machines, it can be more complicated. Microsoft has two mechanisms that are part of the OS to control which

users can use which applications:

Software restrictive policies Employed via group policies and allow significant control over applications, scripts, and executable files. The primary mode is by machine and not by user account.

User account level control Enforced via AppLocker, a service that allows granular control over which users can execute which programs. Through the use of rules, an enterprise can exert significant control over who can access and use installed software.

On a Linux platform, similar capabilities are offered from third-party vendor applications.

AppLocker AppLocker is a component of Windows 7 and later that enables administrators to enforce which applications are allowed to run via a set of