(also NIPS, intrusion prevention system)
Hardware or software measures to protect networks from cyber attacks. These systems constantly monitor networks for threats and automatically take action (such as blocking traffic, killing processes, or quarantining files) when one is detected.
Fail2Ban is an open-source host-based IPS that monitors log files and automatically takes action against suspicious IP addresses.
OpenWIPS-NG is an open-source Linux IPS for wireless networks. It checks suspicious activity for possible intrusion patterns and blocks invaders if necessary.