"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.
"I do not issue any guarantee that this will work for
you...!"