rblspy is an irssi script that checks a list of DNSRBLs for hosts that join a channel. If that host matches, the match can be announced to the channel, reported to the client or automatically banned with a short knockout (to prevent filling the banlist). This script is designed to assist in managing abuse from anonymous proxies.

Supports:

Channel announcements
Automatic bans
Encoded IP usernames from web clients



Check it out on Google Code:
http://code.google.com/p/rblspy/