I have a site which runs phpBB, on this site I have

• enabled user authentication through email when registering
• enabled captcha

However I still get spam users every 20 to 30 minutes.

Is there anything I can do to prevent this with the ucp.php file?

I have already loaded a large list of IP addresses yet there are spam users registering all the time.

One thing I can do is I can check the bounce mail to find the username and can pipe bounced mails to a php script and immediately delete that user, but I have not got any bounce back from hotmail or some other email clients.

So this way it will catch hold of a certain percent of spam users but there are still a huge amount of users spamming.

What else can I do to prevent spammers abusing my phpBB site?