Which of the following is the most reliable authentication method for remote access?
Correct Answer: B
Explanation/Reference:
A Synchronous token generates a one-time password that is only valid for a short period of time. Once the password is used it is no longer valid, and it expires if not entered in the acceptable time frame.
Incorrect Answers:
A: Although variable callback systems are more flexible than fixed callback systems, the system assumes the identity of the individual unless two-factor authentication is also implemented.
C: Callback systems authenticate a person, but anyone can pretend to be that person. They are tied to a specific place and phone number, which can be spoofed by implementing call-forwarding.
D: The caller ID and callback functionality provides greater confidence and auditability of the caller's identity. However, unless combined with strong authentication, any individual at the location could obtain access.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 196, 696
https://technet.microsoft.com/en-us/library/cc778189(v=ws.10).aspx