This mod stops spambots that provide Profile Information during registration in spite of a message saying "leave the Profile Information blank". An e-mail notification will be send every time there was a spambot registration attempt. The e-mail notification can easily be left out if you wish.
This is the actual mod I have been using on 2 of my forums and I can really recommend it. It does the same thing as the previous modification I mentioned, but it gives the admin an opportunity of adding extra text in the registration process to alert its real potential registrants. Besides this, it contains more fields (the whole profile information section) which is much better.