Our forum recently has been attacked by some spammers.
Since no sane human could post this number of spam messages I think that it was a bot.
Unfortunately, the only way to block the spam bots completely is forcing the users to pass a Turing test (Visual Confirmation) each time they post a message.
I am sure, everyone is familiar with the concept (it's when you're asked to enter the numbers or a phrase that are rendered on a picture with distortions no computer program can recognize).
So, if users are required to pass the Turing test each time they post a message it will be a small inconvenience, but this will block the bots entirely. (Of course, human spammers will remain).
There must be a plugin for phpBB that enables such a function. The only question is whether the other users find it necessary.
So what do you think?
For those, unfamiliar with the concept (though I doubt there will be any) you can look here for an example:
http://www.captcha.net/