Once in a while I get a persistent spammer that can get seemingly limitless email address and IP addresses.
Recently I banned him again and then turned on Registration Approval to review new registrations (usually fruitless.)
The next registration I got was with email Luzifull@gmail.com and IP Address 110.164.249.158.
As a last ditch effort to stop this guy, I tried a google search Luzifull@gmail.com 110.164.249.158
and I got a HIT!
http://www.stopforumspam.com/ipcheck/110.164.249.158OMG! I disallowed the registration with the reason: "because you're an idiot"
Over the next three days I got 4-5 such registrations, all of them appearing on stopforumspam.com.
PLEASE write a MOD that incorporates this wonderful functionality! (they claim they have an API for this very reason.)