I recommend this image-based random registration number hack. It works and it only takes about five to ten minutes to install, not to mention it fucks with very few files.
I haven't checked in a long time. If that's not good enough, you could try this hack. It takes more like 20 minutes to install and is much more expansive, however, but it's practically bot-proof.
Y'know, it probably would take much less effort than dealing with all the spambots in the long (or not so long) run... and it'd be so less annoying for everyone concerned.
Yeah, but then again the entertainment value we get from some of these bots must be taken in to consideration.
Actually that question hack is exactly what I've been looking for. Thanks Xento. Okay, it's installed. You'll all have to log-out and click the register button to see the kind of questions it asks you. It's easy enough to change them if necessary. I've already had to fix them because it was made by a non-English speaking Frenchie (who spells apple as "appel"). We now have: E-mail Verification Visual Confirmation Anti-Bot Question ... to stop spambots. Who wants to bet none of it will work? Alternatively if we have a spam-bot free month, I'll consider turning off the e-mail and visual confirmation just to see if it can stop everything all on its own. Actually, I've disabled visual confirmation now. The both of them was too much and phpBB's CAPTCHA is so broken it's not funny. As of today, all spambot topics have been deleted. All existing spambots have been destroyed. The great cleansing of September 17 is complete. Is the War on Spam over? We shall see. 9/17 NEVER FORGET. If this works here, I'll roll it out at every other forum I administrate.