The property of a system or a system resource being accessible and usable upon demand by an authorized
system entity, according to performance specifications for the system is referred to as?

A.
Confidentiality

B.
Availability

C.
Integrity

D.
Reliability

Explanation:
Availability ensures reliability and timely access to data and resources to authorized individuals. Network
devices, computers, and applications should provide adequate functionality to perform in a predictable manner
with an acceptable level of performance. They should be able to recover from disruptions in a secure and quick
fashion so productivity is not negatively affected. Necessary protection mechanisms must be in place to protect
against inside and outside threats that could affect the availability and productivity of all business-processing
components.
Incorrect Answers:
A: Confidentiality ensures that the necessary level of secrecy is enforced at each junction of data processing
and prevents unauthorized disclosure. This is not what is described in the question.
C: Integrity ensures that data is unaltered. This is not what is described in the question.
D: Reliability could be used to describe the ability of system to serve data. However, data being accessible
when required is described as availability, not reliability.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, p. 23