Rosalind - 12:35 pm on May 21, 2008 (gmt 0)

What kind of captcha are you using? If it's the image captcha, it is possible that this is being broken because image captchas can be cracked. As far as I know there is a mod available for a trivia captcha.

But if you've got the more recent text one already it could be that it's being broken by people paid small amounts to fill them in, people in the third world, for instance.

Have you disabled your member list so that it's not viewable to guests, and disallowed signatures from members who haven't made many posts?

The trouble is, PhpBB is always going to be targeted for spam registrations because of its popularity. The real answer is to move your board to software that makes it easy to remove footprints such as the "powered by" text and other tell-tale signs. Once you move off the beaten track by customising software your spam problem will be greatly reduced.