Security Onion is a free and open source Linux distribution designed for network security monitoring that combines tools like Snort, Suricata, Bro, Sguil and Snorby into a single package for full packet capture, traffic analysis and forensic investigation capabilities. It aims to simplify deploying complex security tools by automatically configuring them and allowing analysts to seamlessly pivot between interfaces to trace network threats. Regular rule updates are also automated to keep detections current with emerging attacks.