Mike, I administer several boards with the latest (3.02) version of phpBB, and had the same problem on two of them. We were autobot spammer free until just a few weeks ago. Now some spammers have finally learned how to autoregister in the front door, and it was definitely were the work of bots, and not live person registrations. Last week I enabled GD CAPTCHA, (ACP --> Board Configuration --> Visual confirmation settings), set the x and y axis noise to 20 (still readable, but very hard for bots to crack), and we haven't had any spammer signups since.