I know, you have a lot of SPAM on your forum at last time.
Its caused by XRumer - popular tool for webspam.

But now we have a SPECIAL solution. Its not just a protection from bots.
Its crashes all spambots, they just stop working!

How it works?

Spambots have some bugs, so if your forum contains SPECIAL code - Its caused spambots to crash (and crashes system of a spammer).

How to use AntiXRumer mod?

just download mod here:
https://rapidshare.com/files/2824022752/AntiXRumer_1.0.0_product_for_vBulletin_3-and-4_nix-and-win.zip

And install its on your vbulletin forum. You will forget all SPAM, and - you will help to other admins and for me to: spambot crashes on your forum and, will not come to other forums.
Good luck. Hope we fight them together.

P.S. I can make demo-video, how its really works. If you need.