The Web Security Gateway is a security-centric distribution of the Apache web server, bundled with additional security modules, and configured as a front-end (reverse) HTTP proxy. The goal is to mirror most of the features of commercial web application “firewalls”, with free and Open-Source software.
The Web Security Gateway provides a configurable caching, authentication, input validation, [...]

What Is Mod AntiTamper (AT)
AntiTamper is an Apache 2.x module that could be used to prevent some sort of url and cookie tampering.
Specifically, AT could stop a lot of those malicious bots that take advantage from search engines. Moreover, attack techniques like HTTP Response Splitting and session hijacking/fixation will be mitigated.

Is important to notice that [...]

To follow on from Whitetrash which I posted about previously, here is another tool to secure your web site or web application. Essentially it’s a very comprehensive set of rules for mod_security.
ModSecurity is an open source intrusion detection and prevention engine for web applications (or a web application firewall). Operating as an Apache Web server [...]

Sandcat allows web administrators to perform aggressive and comprehensive scans of an organization’s web server to isolate vulnerabilities and identify security holes.
The Sandcat scanner requires basic inputs such as host names, start URLs and port numbers to scan a complete web site and test all the web applications for security vulnerabilities.
This is a pretty nifty [...]