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Chapter 6

Depth

Cyber Attacks

Protecting National Infrastructure, 1st ed.

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Any layer of defense can fail at any time, thus the introduction of defense in depth
A series of protective elements is placed between an asset and the adversary
The intent is to enforce policy across all access points

Chapter 6 – Depth

Introduction

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Fig. 6.1 – General defense in depth schema

Chapter 6 – Depth

Quantifying the effectiveness of a layered defense is often difficult
Effectiveness is best determined by educated guesses
The following are relevant for estimating effectiveness
Practical experience
Engineering analysis
Use-case studies
Testing and simulation

Chapter 6 – Depth

Effectiveness of Depth

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Chapter 6 – Depth

Fig. 6.2 – Moderately effective single layer of protection

When a layer fails, we can conclude it was either flawed or unsuited to the target environment
No layer is 100% effective—the goal of making layers “highly” effective is more realistic

Chapter 6 – Depth

Effectiveness of Depth

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Chapter 6 – Depth

Fig. 6.3 – Highly effective single layer of protection

Chapter 6 – Depth

Fig. 6.4 – Multiple moderately effective layers of protection

A national authentication system for every citizen would remove the need for multiple passwords, passphrases, tokens, certificates, and biometrics that weaken security
Single sign-on (SSO) would accomplish this authentication simplification objective
However, SSO access needs to be part of a multilayered defense

Chapter 6 – Depth

Layered Authentication

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Chapter 6 – Depth

Fig. 6.5 – Schema showing two layers of end-user authentication

Chapter 6 – Depth

Fig. 6.6 – Authentication options including direct mobile access

Layered E-Mail Virus and Spam Protection

Commercial environments are turning to virtual, in-the-cloud solutions to filter e-mail viruses and spam
To that security layer is added filtering software on individual computers
Antivirus software helpful, but useless against certain attacks (like botnet)

Chapter 6 – Depth

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Chapter 6 – Depth

Fig. 6.7 – Typical architecture with layered e-mail filtering

Layering access controls increases security
Add to this the limiting of physical access to assets
For national infrastructure, assets should be covered by as many layers possible
Network-based firewalls
Internal firewalls
Physical security

Chapter 6 – Depth

Layered Access Controls

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Fig. 6.8 – Three layers of protection using firewall and access controls

Chapter 6 – Depth

Five encryption methods for national infrastructure protection
Mobile device storage
Network transmission
Secure commerce
Application strengthening
Server and mainframe data storage

Chapter 6 – Depth

Layered Encryption

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Chapter 6 – Depth

Fig. 6.9 – Multple layers of encryption

The promise of layered intrusion detection has not been fully realized, though it is useful
The inclusion of intrusion response makes the layered approach more complex
There are three opportunities for different intrusion detection systems to provide layered protection
In-band detection
Out-of-band correlation
Signature sharing

Chapter 6 – Depth

Layered Intrusion Detection

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer

Chapter 6 – Depth

Fig. 6.10 – Sharing intrusion detection information between systems

Developing a multilayered defense for national infrastructure would require a careful architectural analysis of all assets and protection systems
Identifying assets
Subjective estimations
Obtaining proprietary information
Identifying all possible access paths

Chapter 6 – Depth

National Program of Depth

The University of Adelaide, School of Computer Science

Chapter 2 — Instructions: Language of the Computer