What I have is scammers from Nigeria and Ghana joining my service and purchasing a paid membership with stolen credit cards and this has cost me a lot of money. What I need is a way to create a question which has an answer that is common knowledge amongst the community I'm dealing with. So when people try to join they have to enter the answer to the question correctly prior to being able to submit the registration form. Kind of similar to account verifications on banking sites, where they ask a question like what is your mothers maiden name, before allowing login. I need something like that but with a question and answer that's common knowledge amongst the community. What would be the best method to accomplish this?