@Caito: Currently there are already f1 related questions, and they were effective only for some time after we ditched the broken CAPTCHA coding
@Caito: De-indexing the forum is not going to happen. Search engines bring 45% of daily visitors, and a large part of that is to the forum.
Preventing new users to post new threads I believe is not wise. I am much opposed to any spamfighting rule that limits the possibilities of bonafide users.
As mentioned, there is a anti-spam measure in place which detects spamwords in usernames, emails, signatures etc. However, after 10 auto-banned users, suddenly users have no more signature, but instead post the links in the post itself. Next step is to extend this detection to the posts' content, as current spammers really like episodes and movies
It really is a difficult problem, thanks for the ideas!