Apparently some foreign spammer found an exploit in this version of vBulletin and used it to send out a ton of spam from my server with the following subject:

Subject : Welcome to Anal SEX Forums at www .***** .com .cn

This happened at around midnight tonight.

I *'d out part of the URL so it doesn't get any further google help from this site.

No idea what they are exploiting yet.

Has something to do with the e-mail system that verifies users.