Via Bruce Schneier’s blog we get some pictures of ATM card skimmers. Take a look at the pictures and you’ll see how hard it is to tell if you’re inserting your card into an ATM alone.
ATM skimmers are little devices that criminals attach to the card reader of an ATM. What it does is read the number from the card and somehow either store it for later retrieval or send the number to the criminal. It doesn’t interfere with the operation of the ATM so while the criminal gets your card number you simply get your money and receipt from the ATM. As the pictures in the linked article shows it’s very difficult to tell whether a skimmer as been attached to an ATM.