The Open Web Application Security Project Home Page: www.owasp.org

The official mod_security home page, where you can obtain source code, official documentation and links to external resources as well: www.modsecurity.org

“Introducing mod_security”, by Ivan Ristic, mod_security's creator: www.onlamp.com/pub/a/apache/2003/11/26/mod_security.html

“What's New in ModSecurity”, by Ivan Ristic. An overview of mod_security 1.9's new features: www.onlamp.com/lpt/a/6350

“ModSecurity For Apache User Guide” (for mod_security 1.9): modsecurity.org/documentation/modsecurity-apache-manual-1.9.html