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.
For ModSecurity to be effective it needs a rule set just like any IDS or Anti-virus solution, gotroot currently provides the largest selection of rules to secure your site.
This is only an option if you are using Apache 1.x or Apache 2.x if you are using IIS or another web server you are out of luck.
If you run any kind of web application, you need a web application firewall. Simply put, a web application firewall analyzes the connections to your web application to make sure they don’t contain attacks, viruses, worms or violate certain rules about normal or acceptable behavior for your web application(s).
The gotroot rules protect against all of that, and more, such as SQL injection protection, URI formating protection, meta and null character filtering, path recursion attack protection, buffer and heap overflow defenses, remote file inclusion attack prevention and many many others. This helps to protect your web server, applications, database or anything else your web application(s) have potential access to from attack.
This is to protect the application level – firewalls only examine packets on the network level, IDS can do a little on the application side but not as much as ModSecurity and a good set of rules.
You can find the gotroot rules here:
Including instructions on how to download/update them automatically.