ModSecurity

ModSecurity is a web application firewall engine that inspects HTTP traffic and applies rules to protect web applications from a range of attacks. It loads and interprets rules written in the ModSecurity SecRules format, then applies them to HTTP content.

The engine supports HTTP traffic monitoring, logging, and real-time analysis, with an event-based programming language for request handling and intervention decisions. The v3 library, libmodsecurity, removes the Apache dependency and connects to web servers through separate connectors for Apache, IIS, and Nginx.

ModSecurity v3 is a complete rewrite of the platform, while ModSecurity for Apache v2.x remains under maintenance. It is written in C++ and builds on Linux, macOS, and other Unix-like systems.