August 2015: New ATM "Shimmer" Found in Mexico
A skimmer is a credit card reader that is placed on an ATM that records the data on the magnetic strip of your ATM card. That data can then be used to create a duplicate card. Once that data has been collected, the only other thing needed is your PIN. The PIN could then be collected with either a small pinhole camera or a keypad overlay. A keypad overlay is essentially a fake keypad that sits overtop of the actual keypad and records your PIN.
A new type of ATM skimmer has been discovered by security experts in Mexico. It is known as a "shimmer" because it acts as a shim between the credit card and the real card reader inside the ATM. These new shimmers can be incredibly difficult to find as they are completely concealed within the ATM card reader.