> If your site does anything abnormal (whether it's 'what's n+n?' or 'what popular figure comes through your chimney in December?') a bot is hopeless.
I run a forum using Invision Power Boards, which has a built in question-and-answer verification during registration. Soon after I set it up I watched a bot in the server logs completing the registration in only a couple seconds.
I suspect that because IPB is a big enough target, they farm out the questions just like they farm out CAPTCHAs, and build a database of questions and answers. You'd need to include some randomness in the questions to throw them off.
I run a forum using Invision Power Boards, which has a built in question-and-answer verification during registration. Soon after I set it up I watched a bot in the server logs completing the registration in only a couple seconds.
I suspect that because IPB is a big enough target, they farm out the questions just like they farm out CAPTCHAs, and build a database of questions and answers. You'd need to include some randomness in the questions to throw them off.