Howtoforge published a guide about blocking Spammers/Hackers with mod_defensible on Apache2

mod_defensible is an Apache 2.x module intended to block spammers/hackers/script kiddies using DNSBL servers. It will look at the client IP and check it in one or several DNSBL servers and return a 403 Forbidden page to the client. This guide shows how to install and use it with Apache 2 on a Debian Etch server.

How To Block Spammers/Hackers With mod_defensible On Apache2 (Debian Etch)