Check DNSBL
 

This is a simply plugin that will check a poster's host with a so called DNS Blacklist.
By default it will only check the host of unregistered or not logged in users. I have a few forums that allow guest to post and recently they have been visited by spammers, this plug stopped them.

You can enable it so it will check for all posters but it's not adviced, specially when you have a large forum

By default it will use SpamHaus' sbl+xml DNSBL, eventhough SpamHaus focus is on email spam the same spammers also spam forums (or so it seems). Anyway, you can configure the DNSBL to use via the vbulletin settings.

we already have seen two different hacks related to the DNSBL, please use the search tool and browse the forums before releasing similar addons, maybe you will spare some times!

well, it only to me 30 minutes to write it (and another 15 to make it "nice")

but still, the other "DNSBL/Open Proxy-Blocking" does more than I needed it to do