Snort

Zeek (formerly Bro) is the world’s leading platform for network security monitoring. Flexible, open source, and powered by defenders. Zeek has a long history in the open source and digital security worlds. Vern Paxson began developing the project in the 1990s under the name “Bro” as a means to understand what was happening on his university and national laboratory networks. Vern and the project’s leadership team renamed Bro to Zeek in late 2018 to celebrate its expansion and continued development. Zeek is not an active security device, like a firewall or intrusion prevention system. Rather, Zeek sits on a “sensor,” a hardware, software, virtual, or cloud platform that quietly and unobtrusively observes network traffic. Zeek interprets what it sees and creates compact, high-fidelity transaction logs, file content, and fully customized output, suitable for manual review on disk or in a more analyst-friendly tool like a security and information event management (SIEM) system.

OSSEC is fully open source and free, you can tailor OSSEC for your security needs through its extensive configuration options, adding custom alert rules and writing scripts to take action when alerts occur. Atomic OSSEC helps organizations meet specific compliance requirements such as NIST and PCI DSS. It detects and alerts on unauthorized file system modification and malicious behavior that could make you non-compliant. The Atomic OSSEC open source-based detection and response system adds thousands of enhanced OSSEC rules, real-time FIM, frequent updates and software integrations, built-in active response, a graphical user interface (GUI), compliance tools, and expert professional support. It’s a versatile XDR and compliance all-in-one security solution.