CHAPTER 4

Question 1

This chapter presents the following:

Answer 1

• System architecture
• Computer hardware architecture
• Operating system architecture
• System security architecture
• Trusted computing base and security mechanisms
• Information security software models
• Assurance evaluation criteria and ratings
• Certification and accreditation processes

Question 2

Because maintenance hooks are usually inserted by programmers, they are the ones who usually have to take them out before the programs go into production. Code reviews and unit and quality assurance testing should always be on the lookout for back doors in case the programmer overlooked extracting them. Because maintenance hooks are within the code of an application or system, there is not much a user can do to prevent their presence, but when a vendor finds out a back door exists in its product, it usually develops and releases a patch to reduce this vulnerability. Because most vendors sell their software without including the associated source code, it may be very difficult for companies who have purchased software to identify back doors. The following lists some preventive measures against back doors:

Answer 2

• Use a host intrusion detection system to watch for any attackers using back doors into the system.
• Use file system encryption to protect sensitive information.
• Implement auditing to detect any type of back door use.

Question 3

The following are the three main goals of integrity models:

Answer 3

• Prevent unauthorized users from making modifications
• Prevent authorized users from making improper modifications (separation of duties)
• Maintain internal and external consistency (well-formed transaction)