It sucks, but maybe have a set up where the first ten posts from a new member have to be approved. It makes extra work for mods and admins, but it would force new members to have to post within the guidelines of the forum before exposing themselves as spammers.
Set it up so they don't know the posts need approval until they make that first post, then they are busted. The spam never hits the forums. Or, make it so they do know they need approval. That usually makes spammers look elsewhere for a forum that is not moderated.
|