Authorities in Shenandoah and Red Oak have issued warnings about incidents of gas pump skimming. According to a press release, Red Oak Police found a card skimmer on a gas pump. And, the Shenandoah Police Department warned people to exercise caution when using a credit or debit card at the pump, even though no skimmers have been found in Shenandoah.

Authorities say the skimmers are almost impossible to spot. They recommend you use your card to pay at the store’s inside register, and check your bank/credit card statements often to make sure no extra charges have appeared on your account. If you notice any unusual charges, notify your bank or credit card company immediately.

Experts say skimmers look and act like installed gas pump card readers. They can be installed devices, invisible to staff and customers, which read details off credit and debit cards and can even secretly, film the keying of PIN numbers. The thief has to come back to the compromised machine to pick up the file containing all the stolen data, but with that information in hand they can create cloned cards or just break into bank accounts to steal money.

One way to determine if the gas pump has been compromised is if the security seal over the installed card reader is broken, or looks like it has been tampered with.