Credit card skimmers are devices that store credit card information when a card is run through them so that a thief can then use such information to make fraudulent charges on the card, according to About.com. Such skimmers can either be attached to a handheld device and used by people like waiters outside of the view of the owner or inserted into other devices, such as automated teller machines or movie rental kiosks.
Such skimmers are effective in committing fraud because the owner may not be aware of the fraudulent charge until he receives a monthly bill much later, warns About.com. One of the best ways to prevent such thefts or catch them immediately is to make a habit of checking charge accounts frequently to detect any unusual activity. Another method of prevention involves the user keeping an eye on the card when handing it over for a purchase.
One way to prevent credit card information from being stolen at an ATM is to be vigilant of any unusual details, such as an attachment on a machine or a camera pointed at a keypad, states About.com. Thieves often use video to steal personal identification numbers from users, which they can then use in combination with card number information to remove funds from accounts.