If any of you guys and gals run vBulletin and are getting plagued with forum spam I would like to direct you to the most valuable vbulletin plugin I have come across to date. And I am not saying that just because we made the mod... it :) It really works!
Stop vBulletin Spam
Its based off of an older unsupported mod.
This has significantly curbed the number of daily spam posts from 3-10 per day to <1 per day since we installed it.