Sagan is an open source (GNU/GPLv2) multi-threaded, high performance, real-time log analysis & correlation engine developed by Quadrant Information Security that runs on Unix operating systems. It is written in C and uses a multi-threaded architecture to deliver high performance log & event analysis. Sagan's structure and rules work similarly to the Sourcefire Snort IDS/IPS engine. This allows Sagan to be compatible with Snort or Suricata rule management software and gives Sagan the ability to correlate with Snort IDS/IPS data.

Sagan supports different output formats for reporting and analysis, log normalization, script execution on event detection, GeoIP detection/alerting and time sensitive alerting.