Abstract
Automatic teller machines have given customers banking at leisure. Unfortunately such convenience is coming at a price that sometimes can be costly. While external ATM problems have been causing nightmare to both customers and the banking industry, vulnerabilities to ATM systems are enticing unethical insiders to cause customers damage from within. Recently, researchers detailed an elegant attack that yields a customer's personal identification number in as low as 15 tests. This paper demonstrates the attack in simpler terms and then suggests a hardening scheme for the vulnerability. The proposed hardening scheme is demonstrated at both the hardware and software level.