We are having a problem with a user who comes to our site to attempt to validate hundreds of credit card numbers. He will run around 400+ $1.00 transactions at a time, find some valid card numbers and then quit. This is happening with more frequency.
He uses the same name and address each time and his IP address is the same. We are taking several steps to address the issue.
One of the steps I would like to take is to prevent him from submitting the transaction if I see his IP address. Is it safe to do this? Could I potentially be losing legitimate sales by doing this?
BTW, we use PayPal's Payflow pro service to process credit cards.