Suricata!

Snort® is an open source network intrusion prevention and detection system (IDS/IPS) developed by Sourcefire. Combining the benefits of signature, protocol, and anomaly-based inspection, Snort is the most widely deployed IDS/IPS technology worldwide. With millions of downloads and nearly 400,000 registered users, Snort has become the de facto standard for IPS.

PacketSled is next generation network forensics and breach detection.

The ultimate real time network visibility and active cybersecurity platform based on Big Data and Open Source. is a Operational Intelligence Platform to analyze network traffic.The first stage is in charge of collecting, in an scalable way, network data in multiple native protocols. This simplifies the inter-operativity process with all the different network elements present in your IT environment without the need for a complex ETL process.Each protocol is covered by a C program, using Zookeeper for cluster synchronization (in pay versions), and licensed under AGPL (some are proprietary due to licensing limitations). »