See also #secure.
Intrusion detection is the process of monitoring the events occurring in a computer system or network and analyzing them for signs of possible incidents, which are violations or imminent threats of violation of computer security policies, acceptable use policies, or standard security practices.
Quality of a software application that its network or itself is monitored for malicious activity or policy violations.
Derived from Wikipedia/Intrusion Detection System
Quality of a software application that it is monitored by another system that detects suspicious activities.
Derived from Checkpoint/Intrusion Detection System