From the modsecurity website (cache): "ModSecurity is an open source intrusion detection and prevention engine for web applications (or a web application firewall). Operating as an Apache Web server module or standalone, the purpose of ModSecurity is to increase web application security, protecting web applications from known and unknown attacks." modsecurity was written by Ivan Ristic of Thinking Stone Ltd. The GotRoot? modsecurity rules are written and maintained by Michael Shinn, of Prometheus Group.

How to download, install, setup and configure mod_security

mod_security rules: Signatures and Rules for modsecurity/mod_security.

mod_security: Downloads for the mod_security Apache module.

http://www.modsecurity.org/ (cache)

ModSecurity (or mod_security) is an open source intrusion detection and prevention engine for web applications written by Ivan Ristic. Operating as an Apache Web server module, the purpose of ModSecurity is to increase web application security, protecting web applications from known and unknown attacks.

Setting up mod_security: How to setup, compile and install mod_security in less than 5 minutes.

mod_security rules: Configuring Mod_Security and adding in rules.

Official Documentation for mod_security (cache)

Download rules for the mod_security apache Intrusion Prevention System?.

Introducing mod_security (cache)