How secure are today's ATMs? 5 questions answered

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Pradeep Atrey, University at Albany, State University of New York

(THE CONVERSATION) Editor’s note: Automated teller machines, better known as ATMs, are turning 50 on June 27. Computer science professor Pradeep Atrey, from the University at Albany, State University of New York, explains the security features and concerns of modern cash machines.

1. How does an ATM work?

In the broadest sense, an ATM works by accepting a cash request from a user, verifying the user’s authority to access a particular bank account, ensuring that account has enough money to fulfill the request and dispensing the money – all without the assistance of a bank clerk or teller.

From the very beginning, all the way back to the first ATM placed in use in London in 1967, the user’s identity was the main problem banks needed to solve. Rather than today’s plastic card with a magnetic strip and embedded microchip, the first machine accepted a slip of paper with a mildly radioactive substance – carbon-14 – printed on it in a particular pattern. The machine matched the pattern to a number code entered by the user. If it matched, and if the funds were available, the machine dispensed up to £10 (an amount worthjust over US$200 today).

When using modern ATMs, a customer inserts a plastic card into the machine’s reader, which registers either the data encoded on the card’s magnetic strip or its embedded chip. It prompts the customer for a personal identification number, usually called a PIN, often four or six digits long.

If the card and PIN match, then the customer can deposit money, check an account balance or, most commonly, request a cash withdrawal. When the customer...