Apparently vBulletin version 3.7 has a couple new features to help if Crim wants to upgrade.
[vB 3.7] How to Reduce Spam and Registration Bots
Also here's a list of known free e-mail addresses that can be black listed from registration to help.
List of Email domains to ban
As the new spammers come in, their e-mail domains can be added to the list as well. Might help some.
The real question is, are they automated spam attacks, or is it someone in a 3rd world country being paid pennies to spam? The automated spammers are easier to take care of.
I'd hate to see us have to resort to the easy but very annoying tactics of many other forums by treating new people like lesser members.