Software that automates the intrusion detection process.
Sources:
NIST SP 800-12 Rev. 1
under Intrusion Detection System (IDS)
from
NIST SP 800-94
A security service that monitors and analyzes network or system events for the purpose of finding, and providing real-time or near real-time warning of, attempts to access system resources in an unauthorized manner.
Sources:
NIST SP 800-82r3
under intrusion detection system
from
RFC 4949 - adapted
Software that looks for suspicious activity and alerts administrators.
Sources:
NISTIR 7711
under Intrusion Detection System