Explanation/Reference:
The data link layer (layer 2) establishes the communications link between individual devices over a physical link or channel. It also ensures that messages are delivered to the proper device and translates the messages from layers above into bits for the physical layer (layer 1) to transmit.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page
83).

Section: Analysis and Monitoring
Explanation/Reference:
There are two conceptual approaches to intrusion detection. Knowledge-based intrusion detection uses a database of known vulnerabilities to look for current attempts to exploit them on a system and trigger an alarm if an attempt is found. The other approach, not as common, is called behaviour-based or statistical analysis- based. A host-based intrusion detection system is a common implementation of intrusion detection, not a conceptual approach.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page
63).
Also: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 4:
Access Control (pages 193-194).

Explanation/Reference:
An early standard for encrypting HTTP documents, Secure HTTP (S-HTTP) is designed to send individual messages securely. SSL is designed to establish a secure connection between two computers. SET was originated by VISA and MasterCard as an Internet credit card protocol using digital signatures. Kerberos is an authentication system.
Source: KRUTZ, Ronald L & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 89.

Section: Network and Telecommunications
Explanation/Reference:
TACACS+ is a proprietary Cisco enhancement to TACACS and is more robust than RADIUS. PAP is not a remote access authentication system but a remote node security protocol.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page
122).

Explanation/Reference:
Single Loss Expectancy (SLE) is the dollar amount that would be lost if there was a loss of an asset.
Annualized Rate of Occurrence (ARO) is an estimated possibility of a threat to an asset taking place in one year (for example if there is a change of a flood occuring once in 10 years the ARO would be .1, and if there was a chance of a flood occuring once in 100 years then the ARO would be .01).
The following answers are incorrect:
gross loss expectancy x loss frequency. Is incorrect because this is a distractor.
actual replacement cost - proceeds of salvage. Is incorrect because this is a distractor.
asset value x loss expectancy. Is incorrect because this is a distractor.