Thanks Dien.
I think installing the akismet plugin should take care of 99% of the spam.
http://www.vbulletin.org/forum/showthread.php?t=118421
And - instead of adding a moderation queue for anonymous posters, just make it so that anonymous posters can post no links. Only registered posters can post links. It'll save a lot of time.
Take away the linking abilities and the spam should go away.