Starting yesterday, we've been getting spam messages from new users. Usually it looks like this: someone registers and shoots seven or eight messages\new topics in a row - posts are meaningless and irrelevant(sometimes it's reposted postings from other forums), but signatures contain links/adverts. We're not doing anything big yet - for now we're just deleting them.
Just so you know: if you see a strange, irrelevant post and spam-like signature, you may be dealing with a bot.