There's a plugin for phpBB that adds reCaptcha to the registration page. That'll keep the damned spambots from registering. I'm sure you've seen it elsewhere:

It's pretty easy... free registration at reCaptcha.net, and then you simply plug the keys into your Admin panel page. Xrumer (the Russian tool that allows the spammers to break your current registration page) can't bypass it, and ALL new registrations will only be people.
I think that ONE of the versions of IE has problems with it... if someone can't get it to work, they need to (briefly) set porn9.org as 'trusted' in the IE settings 'cos of the off-site <IFRAME>, but the other versions of IE are fine, and no other browsers have any issues with it.
If you don't do it, you'll forever be playing Whack-a-Mole with the fucking spambots.
Merely trying to help, NOT trying to tell you how to run your forum!
You undoubtedly have a bunch of 'em already registered that haven't posted yet. They'll be back. The way some people have that spam tool set up, it'll register a user and then wait for a few weeks, then it'll come back some day and do a bunch of spam posts. The rest of the time, it'll register, come in and put some weird shit in it's profile and then hurriedly post a handful of crap on your forum, all within the space of a few seconds.