Security Onion

Security Onion is a free, Linux-based distribution that bundles the best open-source network security tools into a single, cohesive platform. It includes Zeek, Suricata, Wazuh, and a powerful ELK stack for log management and visualization. It is designed to be a complete 'all-in-one' solution for network security monitoring and incident response. While it requires a dedicated server and some technical knowledge to set up, it provides a level of capability that would cost thousands of dollars in commercial licensing.

It is the ultimate tool for budget-conscious organizations that want enterprise-grade visibility.