Your neighborhood ATM has always been a tempting target. From a physical attack standpoint, enterprising fraudsters drill holes to get at the USB slot, hide skimmers in the card readers, hammer them with bull dozers and explode them with bombs. They also play on the vulnerabilities of the cash dispenser, and one variation of that is Transaction Reversal Fraud (TRF). In summary, a TRF is a sophisticated attack involving a sequence of events that generate multiple error codes and an unnecessary payment reversal. These attacks can be tricky to isolate and detect before financial losses occur, especially if changes to the ATM host applications are required.