ModSecurity is an intrusion detection and prevention engine for Web applications (sometimes called a Web application firewall). Operating embedded or as part of an Apache reverse proxy, it increases Web application security, protecting Web applications from known and unknown attacks. It is flexible and easy to configure. It monitors HTTP traffic (including POST payloads), detects or prevents attacks, enhances logging, performs anti-evasion, and allows administrators to create custom rules to suit their specific needs. It excels in HTTP traffic monitoring and just-in-time vulnerability patching.

Webservers and tools around it