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One Step Ahead
January 20, 2009, Volume 55, No. 18

One Step Ahead

Another tip in a series provided by the Offices of Information Systems & Computing and Audit, Compliance & Privacy.

Credit Card Theft: "Skimming"

Over the last couple of years there have been several reports in the media about “skimmers” found attached to ATM machines and credit-pay gas pumps in the Philadelphia region, notably at several Wawa convenience stores. “Skimmers” are small electronic devices which read, store and, in some cases, transmit the digital information from the magnetic stripe of any credit or debit card passed through it—name, account number, expiration date, etc. “Skimming” has become a major factor in the growth of credit card and identity theft over the last decade, and it’s certainly not limited to convenience stores: any commercial or financial business where credit card readers are present is a potential target for “skimming,” including restaurants. In 1999, two waiters in a New York City restaurant were convicted of “skimming” more than $300,000 from diners.

This highlights the fact that “skimming” is often an “inside job” carried out by one or more employees of the business, either on their own or in collaboration with outsiders. The devices used can range from “snapover” readers that fit on top of the legitimate reader to small pocket-sized devices that can be easily concealed and used by crooked waiters, clerks, etc. A similar device called a “card trap” installed on an ATM will fit over the card slot. An inserted card will not be returned, and when the frustrated customer gives up and leaves, the device is simply removed by the “skimmer,” who now has a valid credit card (and possibly even a PIN, if he’s been “shoulder surfing”).

Detecting “skimming” and “card trapping” is very difficult, and many victims only discover it when their statements arrive. Here are a few suggestions from law enforcement experts in this field to help combat it, though:

• Try to limit your ATM use to a few machines with which you are familiar (and better prepared to notice when something is different) and/or machines that are in more secure, controlled areas (such as bank lobbies or vestibules). Also, ATM’s with security cameras are less vulnerable.

• When paying by credit card in person, be observant of how the employee handles your card, and try not to let the card be out of your sight.

• Many credit card companies are now issuing cards on which the information on the stripe is encrypted. Check with your card issuer to see if they currently do this, and if not, when they plan to implement it.

• Above all, check your account statements as soon as they arrive, and report any discrepancies immediately. Law enforcement authorities cite timely reporting as the major factor in identifying and prosecuting “skimmers.”


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For additional tips, see the One Step Ahead link on the Information Security website: www.upenn.edu/computing/security/.

Almanac - January 20, 2009, Volume 55, No. 18