Cloud Computing

There is an increasingly prominent trend in many organizations to move a substantial portion of or even all information technology (IT) operations to an Internet-connected infrastructure known as enterprise cloud computing.  As we know, with every technology there are security considerations.  For this discussion, please provide a thorough response to the below questions.

1. Define cloud computing.
2. List and briefly define three cloud service models.
3. What is the cloud computing reference architecture?
4. Describe some of the main cloud-specific security threats.