Suricata IDS is a free intrusion detection/prevention system and network security monitoring engine. This is a list of awesome things that go with it.
Log configurations and scripts for host intrusion detection system. iptables, syslog and psad configs are here because they are becoming hard to otherwise manage. Configs for various systemd units, rsyslog, psad, logrotate, iptables. Tabkey completion files for bash. Manpages. A couple of scripts for managing running settings.
A daemon that runs on a *nix machine that simulates a network of other systems (of many different operating systems) for the purposes of catching and monitoring intruders.