How Cyber Sleuths Cracked an ATM Shimmer Gang

In 2015, police departments worldwide started finding ATMs compromised with advanced new “shimming” devices made to steal data from chip card transactions. Authorities in the United States and abroad had seized many of these shimmers, but for years couldn’t decrypt the data on the devices. This is a story of ingenuity and happenstance, and how one former Secret Service agent helped crack a code that revealed the contours of a global organized crime ring.


Jeffrey Dant was a special agent at the U.S. Secret Service for 12 years until 2015. After that, Dant served as the global lead for the fraud fusion center at Citi, one of the largest financial institutions in the United States.


Not long after joining Citi, Dant heard from industry colleagues at a bank in Mexico who reported finding one of these shimming devices inside the card acceptance slot of a local ATM. As it happens, KrebsOnSecurity wrote about that particular shimmer back in August 2015.


This card ‘shimming’ device is made to read chip-enabled cards and can be inserted directly into the ATM’s card acceptance slot.


The shimmers were an innovation that caused concern on multiple levels. For starters, chip-based payment cards were supposed to make it far more expensive and difficult for thieves to copy and clone. But these skimmers took advantage of weaknesses in the way many banks at the time implemented the new chip card standard.


Also, unlike traditional ATM skimmers that run on hidden cell phone batteries, the ATM shimmers found in Mexico did not require any external power source, and thus could remain in operation collecting card data until the device was removed.


When a chip card is ..

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