Prevention of damage to, protection of, and restoration of computers, electronic communications systems, electronic communications services, wire communication, and electronic communication, including information contained therein, to ensure its availability, integrity, authentication, confidentiality, and nonrepudiation.
NISTIR 7621 Rev. 1 under Cybersecurity
the prevention of damage to, unauthorized use of, exploitation of, and—if needed—the restoration of electronic information and communications systems, and the information they contain, in order to strengthen the confidentiality, integrity and availability of these systems.
NISTIR 8074 Vol. 2 under Cybersecurity
The process of protecting information by preventing, detecting, and responding to attacks.
NISTIR 8183 under Cybersecurity
(Framework for Improving Critical Infrastructure Cybersecurity, version 1.0)