Schnoz is a tool that I wrote in Python to monitor network traffic and analyze potential threats. I compiled all of the small scripts regarding network analysis to create a multirange tool. Please make sure that you have scapy installed. Implements active network sniffing, pulling from pcap files, alerting on specific traffic parameters, and analysis of captured HTTP traffic.
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.