Posting validation

Hi.

I'm looking for a way to get rid of all spam threads in my PunBB-forum. The forum's open to everyone (no registration needed). I've looked through the threads here in search of some kind of validation mod/plugin/whatever, but the only thing I could find was a couple of word blockers. I'm not sure if this is the easiest solution to my problems? As I mentioned, I want some kind of validation when a user posts a new thread or post. Is there any mod/plugin that works this way?

(Please, excuse my english.)