Last week, Delhi police found that Rs 19 lakh had been fraudulently withdrawn from 87 accounts in three ATMs in the space of seven days.

How was this done?
A skimmer is a device designed to look like and replace the card insertion slot at an ATM. The skimmers, which cannot be usually spotted by an untrained eye, have circuitry that read and store the data on the magnetic strip of an ATM card even as the ATM processes the same data.

Typically, fraudsters also install pinhole cameras in inconspicuous places like the top of the cash dispenser, the deposit slot or just above the keyboard. This steals the PIN for the card. In some cases, criminals have also used a fraudulent PIN pad fitted with a skimming device and placed atop the original pin pad.

Days after installation, criminals recover the skimming machines and cameras and collect the stolen data, and decode the PIN for a card. In one case, in Thiruvananthapuram, data were collected remotely in wireless mode from the skimmer and camera, police said. Using stolen data, the criminals clone ATM cards and use these in different cities; at other times, they transfer the data to associates, or sell the data to other gangs.