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.

This version is usable only with apache 2.2.  See also ap-modsecurity2.

Homepage:
http://www.modsecurity.org/
