by enxio27 » Thu Jan 03, 2013 3:34 pm
Are these spambots or human spammers? You may already know all of this, but on a form I admin, we stopped the spambots cold with a phpBB mod that requires a security question (that requires human thought to answer and can't be looked up in Google) and an upgraded CAPCHA at forum registration. This is on a forum running phpBB2. (I don't have server access, so I can't upgrade to phpBB3, and the owner apparently isn't inclined to do so.) If you are running phpBB3, I believe it comes with the upgraded CAPCHA already, but there's a security question mod for phpBB3 as well. We went from 200+ spambots PER DAY to ZERO as soon as the forum owner installed that mod. We've had a handful of human spammers since then, but even they seem to have decided it's not worth their trouble, as the last one we had was almost a month ago.
You can also install another mod to configure the board to disallow entries in fields such as Website and Signature, so they can't inject their spam into those. Requiring email authentication (selectable in the Admin Control Panel) helped, as well, but I think you already do that.
On that forum, we made all of the forum sections invisible to guests, which removed most of the incentive for spammers. (I wish we could get rid of the googlebots, as well, but that's not my decision to make.) If you don't want to close the forum to registered users only, putting new members on moderated status (as you mentioned) is a good way to combat human spammers, although it's more work for you.