Criminals seeking to steal payment card data are increasingly targeting point-of-sale (POS) terminals. Such illegal activities include accessing POS terminals and inserting a “bug” that reads cardholder data and associated PINs.  Other tactics include installing miniature cameras or video recording devices pointed at PIN-entry devices.

Here are some important steps merchants can take to reduce the risk of having their POS terminals compromised:

• Protect POS equipment – merchants should track POS terminals and their serial numbers; routinely
  inspect terminals and PIN-entry devices to confirm serial numbers and ensure there are no signs of
  tampering.
• Safeguard POS equipment and the surrounding area – to prevent equipment “swaps”, merchants
  should use secure stands, tethers or security cables; check the retail environment for unauthorized
  hidden recording devices; install security cameras.
• Train staff on POS equipment tampering prevention – merchants should help employees recognize the noticeable signs of equipment tampering; validate all POS equipment service and repair technicians.

For more information, please read Visa's in depth article  Point-of-Sale Terminal Tampering.