How do thieves scan credit cards in your purse?

Updated February 21, 2017

A thief cannot scan "conventional" credit cards through the walls of a purse. He can, however, target a new generation of credit cards that use "hands-free" RFID technology. Designed to save consumers time at the checkout counter, hands-free credit cards can be read by the register from a range up to 18 inches.

Each hands-free credit card contains a small device called a "passive RFID tag." This tag consists of a coil of flattened wire connected to a tiny electrical circuit. When a magnetic field of a radio waves strikes the coil, it induces an electrical current within the coil's metal. This electrical energy is collected as voltage inside the card's circuit. Once a certain amount of voltage has been collected, the energy is released into a separate part of the circuit where it is converted into a pattern of electrical pulses. Note: each card produces its own, unique pulse pattern, which contains coded account information.

When this pulse pattern flows back through the coil, it causes the coil to emit a radio wave containing the exact same pattern. Finally, this radio wave is received by a specially-calibrated antenna located inside the register's scanner.

How Thieves Exploit RFID Credit Cards

Radio waves easily penetrate most materials, including glass, brick, fabrics and wood. Therefore, thieves will place RFID scanners inside coats, briefcases, purses and other non-metal containers and simply move through a crowd. The hidden scanner is designed to emit the same radio wave frequency as a checkout counter RFID scanner. When these "imposter" waves pass through the wall of a purse and strike the hands-free card, the card will emit its account-information-containing radio signal back.

This signal passes through the wall of the purse, across the air, past the wall of the hidden scanner's container and into the scanner's receiver. The receiver is attached to a circuit that saves the signal as a data file. Back at home, the thief retrieves the data file and starts buying merchandise online with your credit card information.

How to Foil Would-Be Identity Thieves

Quite simply, use foil! Inserting sheets of aluminium foil inside the lining around your purse will block or "attenuate" both incoming scanner radio waves and any response signals emitted by your card.

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About the Author

A Chicago-based copywriter, Andy Pasquesi has extensive experience writing for automotive (BMW, MINI Cooper, Harley-Davidson), financial services (Ivy Funds, William Blair, T. Rowe Price, CME Group), healthcare (Abbott) and consumer goods (Sony, Motorola, Knoll) clients. He holds a Bachelor of Arts in English from Harvard University but does not care for the Oxford comma.