113. Which of the following is not a single point-of-failure?
a. Mesh topology
b. Star topology
c. Bus topology
d. Tree topology
113. a. A mesh topology is a network in which there are at least two nodes with two or more paths between them. If one path fails, the network reroutes traffic over an alternative path thus providing a high degree of fault tolerance mechanism. Thus, mesh topology is not vulnerable to a single point-of-failure.
The other three choices are subjected to a single point-of-failure. The single central hub in star and tree topology and the single cable in bus topology are vulnerable to a single point-of-failure.
114. Which of the following describes one process signaling information to another by modulating its own use of system resources in such a way that this manipulation affects the real response time observed by the second process?
a. A communication channel
b. A covert storage channel
c. A covert timing channel
d. An exploitable channel
114. c. The statement fits the description of a covert timing channel. A communication channel is the physical media and device that provides the means for transmitting information from one component of a network to other components. An exploitable channel is any channel usable or detectable by subjects external to the Trusted Computing Base (TCB).
115. Which of the following is not vulnerable to a single point-of-failure?
a. Internet
b. Converged network
c. Password synchronization
d. Domain name system server
115. a. Despite its security weaknesses, the Internet is not vulnerable to a single point-of-failure because it uses a point-to-point protocol (PPP) as the primary data link layer protocol over point-to-point lines. PPP handles error detection, supports multiple framing mechanisms, performs data compression and reliable transmission, enables IP addresses to be negotiated at connection time, and permits authentication. If one path or point fails, the Internet switches to another path or point therefore providing a solid connection.
The other three choices are vulnerable to a single point-of-failure. A converged network combines both data and voice, and as such it is vulnerable. Password synchronization can be a single point-of-failure because it uses the same password for many resources. The domain name system (DNS) server can become a single point-of-failure if there are no fault-tolerant and redundant mechanisms.
116. It is best to assume that external computer systems are:
a. Simple
b. Secure
c. Insecure
d. Complex
116. c. In general, external computer systems should be considered insecure. Until an external system has been deemed trusted, it is safe to assume that it is insecure. Systems can be simple or complex in design, which may or may not affect security.
117. Which of the following memory protection mechanisms deal with security impact levels?
a. System partitioning
b. Nonmodifiable executable programs
c. Resource isolation
d. Domain separation
117. a. An organization partitions the information system into components residing in separate physical domains or environments as deemed necessary. Information system partitioning is a part of a defense-in-depth protection strategy. The system partitioning is based on the system impact levels (i.e., low, medium, or high). Managed interfaces restrict network access and information flow among partitioned system components.
The other three choices are incorrect because they do not deal with security impact levels. A nonmodifiable executable program is the one that loads and executes the operating environment and application system from hardware-enforced and read-only media (e.g., CD-R/DVD-R disk drives). Resource isolation is the containment of subjects and objects in a system in such a way that they are separated from one another. Domain separation relates to the mechanisms that protect objects in the system.
118. Which of the following maintains the integrity of information that is sent over a channel?
a. Communication channel
b. Security-compliant channel
c. Trusted channel
d. Memory channel
118. c. A trusted channel maintains the integrity of information that is sent over it. The other three choices cannot maintain the integrity because they are not trusted.
119. Which of the following enforces the network policy?
a. Exploitable channel
b. Communications channel
c. Security-compliant channel
d. Memory channel
119. c. A security-compliant channel enforces the network policy and depends only upon characteristics of the channel either included in the evaluation or assumed as an installation constraint.
120. The use of which of the following can lead to the existence of a covert channel?
a. Data label
b. Dual label
c. Floating label
d. Fixed label
120. c. The covert channel problem resulting from the use of floating labels can lead to erroneous information labels. A fixed label is a part of a dual label.
121. Which of the following is needed for the correct operation of other security mechanisms?
a. Covert storage channel
b. Trusted channel
c. Covert timing channel
d. Overt channel
121. b. A trusted channel is needed for the correct operation of other security mechanisms. An overt channel may not be trusted. A covert storage and timing channel is a part of covert channel.
122. Which of the following determines the extent to which changes to an information system have affected the security state of the system?
a. Information system boundary
b. Information system resilience
c. Security impact analysis
d. Security control assessment
122. c. Security impact analysis is conducted to determine the extent to which changes to the information system have affected the security state of the system.
The other three choices do not deal with security states. Information system boundary means all components of a system to be authorized for operation have a defined boundary, and it excludes separately authorized systems to which the system is connected. Information system resilience is the capability of a system to continue to operate while under attack, even if in a degraded or debilitated state, and to rapidly recover operational capabilities for essential functions after a successful attack. Security control assessment is the testing and/or evaluation of the security controls (i.e., management, operational, and technical controls) to determine the extent to which the controls are implemented correctly, operating as intended, and producing the desired outcome with respect to meeting the security requirements of an information system.