Which of the following is an unintended communication path that is NOT protected by the system`s normal security mechanisms? 

Answer options:

A. A trusted path
B. A protection domain
C. A covert channel
D. A maintenance hook

C

A covert channel is an unintended communication path within a system, therefore it is not protected by the system`s normal security mechanisms. Covert channels are a secret way to convey information. Covert channels are addressed from TCSEC level B2. The following are incorrect answers: A trusted path is the protected channel that allows a user to access the Trusted Computing Base (TCB) without being compromised by other processes or users. A protection domain consists of the execution and memory space assigned to each process. A maintenance hook is a hardware or software mechanism that was installed to permit system maintenance and to bypass the system`s security protections. Reference used for this question: KRUTZ, Ronald L. & VINES, Russel
D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 6: Operations Security (page 219).