I read that you switched to vBulletin to avoid spam--well given your inundation right now with spam you haven't set it up well yet! I have suggestions:

1. vBulletin options drop-down → user registration options → turn on "moderate new members" and then manually accept each new user.

2. Admin control panel → "user profile fields" → select "add a new profile field → select the default single-line text box → hit continue. Now add a question and make it mandatory to answer, say, "what billiards discipline is your main area of interest" A legit member who signs up will have an appropriate answer and spam users usually won't because, they are usually idiots, who know nothing about the topic of your forum, and who don't speak English, and are barely literate, or they are spambots so they will never respond appropriately to a human's question.

3. Next, turn on all the built in all human verification features.

4. Go to "user banning options" and ban all known spam email domains. A list can be found at http://www.joewein.de/sw/blacklist.htm

Best regards,

Three cushion nut