captcha + question at member registration

I use vBulletin (vBSEO). To get rid of the spam bots I want the people that register to do two actions to be able to register. I want them to fill inn captcha and answer a question like 2+2.
I do this another forum (not vBSEO) and have no spam bots, its a great method, but how to do it in vBulletin?

Thanks, green rep to good answers

 

CAPTCHA is default in most forum software now. However there are several modifications for this:

http://www.vbulletin.org/forum/showthread.php?t=183917&highlight=spam

This modification will give you the question you are after: http://www.vbulletin.org/forum/showthread.php?t=183329&highlight=spam

There are lots more here :http://www.vbulletin.org/forum/search.php?searchid=10567558

 

Thanks rockinaway