ModSecurity is a web application firewall that can work either embedded or as a reverse proxy. It provides protection from a range of attacks against web applications and allows for HTTP traffic monitoring, logging and real-time analysis.
It is also an open source project that aims to make the web application firewall technology available to everyone.
It has great features like parallel text matching, Geo IP resolution, credit card number detection, support for content injection, automated rule updates, scripting & much more. You can go and download it from here!
