How to stop all the spam users ?

[Smithyy87]

Well i had a little look at other posts here on the forum but could not really find anything that was of any use to the issue i have.

basically what the problem is , is i keep getting new users to my forums and they are trying to sell me viagra , now this might be a good thing for some people depending on how old you are and how well your man hood kicks into gear but for myself it's rather annoying as im having to delete them each day.

What i wanted to knoe if there was some sort of Addon or somthing available to use to stop this from happening?

Thanks