You have to be very careful if you are having a rfid credit card. By the rfid stands for radio frequency identification. This is a card having a small chip and an antenna. I am sure that most credit cards or ATM cards have either bar code or a magnetic strip on the back. But if you are using a card having rfid, you might be in danger of getting hacked. Crackers can use RFID readers to scan and then copy ID cards.