libapache2-mod-scramble-ip is an Apache 2 module that works like mod_removeip, but instead of just overwriting the IP address with 127.0.0.1, it encrypts the IP address. This way you always get an IP address to work with (in scripts, etc.) and have the ability to use tools like awstats to analyze your logs.
mod_access_identd is a security module for the Apache Web server, supplying mandatory access control based upon the client username and host.
mod_antihak is designed to eliminate the CodeRed and Nimda worm's network bandwidth consumption.
mod_antispam is an apache module which can control referer spam.
mod_clamav is an Apache 2 filter which scans the content delivered by the proxy module (mod_proxy) for viruses using the Clamav virus scanning engine.
mod_evasive is an evasive maneuvers module for Apache to provide evasive action in the event of an HTTP DoS or DDoS attack or brute force attack. It is also designed to be a detection and network management tool, and can be easily configured to talk to ipchains, firewalls, routers, and etcetera. mod_evasive presently reports abuses via email and syslog facilities.
mod_fortress is an application level firewall and intrusion detection system designed to intercept certain CGI/HTTP attacks by acting as a non-transparent proxy between an Apache server and an HTTP client.
mod_gnutls uses the GnuTLS library to provide SSL v3, TLS 1.0 and TLS 1.1 encryption for Apache HTTPD. It is similar to mod_ssl in purpose, but does not use OpenSSL.
mod_parmguard protects your scripts against hacker's input.
mod_protection integrates the basic function of an IDS (Intrusion Detection System) and a firewall. When a malicious client sends a request that matches a rule, the administrator will be warned and the client gets an error message.
mod_removeip anonymizes information about REMOTE_HOST location.
mod_securid enables RSA SecurID authentication for Apache.
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.
mod_sesehe secures a server.
mod_ssl provides strong cryptography for the Apache 1.3 webserver via the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols by the help of the Open Source SSL/TLS toolkit OpenSSL.
In case a SSL connection fails because a certificate is expired, or a CRL is unavailable, etc., the browser receives a SSL error that results in a cryptic technical error displayed to the user. This module allows, in such a situation, to redirect the browser to a page with the specific error message ("Your certificate is expired", "We cannot check the validity of the certificate - retry later", etc.).
mod_stego is an Apache 1.x module. It steganographs a file or a message inside the html pages. If you want the message, you should use a de-steganography software to take it out.
mod_streamav is designed as an Apache 2 filter which scans the content of the Apache Brigades using the Clamav virus scanning engine.
Mod WASap is an Apache module (version 1.3.x), which acts as an Application level Firewall. It can filter and block malignant requests.
scrutinizer is designed to protect Web servers from HTTP (D)DoS attacks. It's a toolkit consisting of an analysis engine which analyzes Web server access logfiles in almost real time, an Apache module which is able to block wrongdoers on the Web server, an extension to block offenders with netfilter firewalls, and a set of visualization tools.