I have thought about my own verification opposed to captcha / digit typing. It would look like this, practically:
I am wondering if anyone that brainstorms can think of vulnerabilities of this sort verification as a replacement of common captcha, these questions can be tons and all in random combinations to eachother per 5 questions. The questions can only be answerred by a human from common sense. To protect from bots learning answers, I plan to add new questions on a daily to weekly basis incase I get to handle some pass-through or bot registrations, and make them blend in on the random combinations.
How safe is this approach and are there any vulnerabilities I have likely not thought of?
I just saw this on a forum and I suspect it's a self-made plugin, so I want to develop that too. If it's not and someone recognizes it (from SimplePortal board soft) please name/identify it.
Another practical example