Abstract: A credit card security device which prevents credit card and bank card fraud. The device includes a case with an access door secured by a lock for storing the cards and a detection member within the case for determining an entry into the case when the door is locked. The detection member operates an electromagnet within the case upon the entry. The electromagnet scrambles the code within each credit card's magnetic strip and thereby invalidates the credit cards for future use. The detection member comprises a normally open electrical circuit when the door is closed and locked and includes switches for providing a current flow to the invalidating electromagnet upon the entry. At least one such switch is a normally open pressure switch mounted in wall of the case which closes when the entry to the case is through the wall, thereby providing the current flow to the electromagnet.