Intrusion Detection System
A system that inspects network activity and identifies suspicious patterns that may someone is attempting to penetrate or compromise a system or network. An IDS: may be network-based or host-based; signature-base or anomaly-based, and requires human intervention in order to respond to the attack.
Reference(s) in IAPP Certification Textbooks: F99-101
Associated term(s): Intrusion Prevention System (IPS)