Im pretty sure there is a option that the administrator can select that makes the person who signs up on the forum have to go into his email to activate his membership. reason im saying this because of profile.php?mode=viewprofile&u=133 so if you make people activate their accounts by email (which im pretty sure the automated spammers can't activate, because its usually a fake email) then it will keep this forum clean
I noticed spammers are still signing up to promote their websites in the memberlist. I therefor (temporarily) disabled the memberlist since it's probably not used anyway. (let me know if I'm wrong)