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 greatÃƒâ€šÃ‚Â 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!