A Reddit user recently posted a photo that serves as an invaluable reminder to stay vigilant at the ATM. The thread, created by user atlas5280, gets straight to the point: "Thanks Reddit. You saved me from potential credit card theft. Always wiggle the card reader."
The device pictured above is called a "card skimmer." They're used by criminals to record debit card data in order to withdraw money from victims' account. These devices are often indistinguishable from legitimate card scanners, and thieves will place them over the real ATM card slot to steal customer information.
A simple, but effective technique to avoid credit card fraud at the hands of these skimmers is a quick wiggle of your card. It may sound silly, but it can help identify fraudulent card readers — movement should loosen any attached skimmers and save you from getting scammed. The wiggle technique even comes recommended by the Secret Service.
It also helps to shield your PIN number with your free hand while you're entering it, so as to block any people or cameras nearby from viewing it, as a number of these skimmer devices still require a PIN to withdraw money from your account.
If you believe your credit card info has been compromised or stolen, contact your bank and the police as soon as possible.