Skimmers have been found on gas pumps, ATMs and cash registers.
Police now say skimmers are becoming so advanced that people tasked with checking for them night not notice the devices.
But Channel 11 has learned there is a way your own cellphone could keep you from becoming a victim.
"About twice a week, there are skimmers found at gas stations," said Matt Hayes, a special agent with the Secret Service.
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Officials in Colorado found a new criminal tool to steal credit and debit card numbers that doesn't include any wires.
"He installs a card slot reader, which is simply held in place by a few screws on the back of the pump door," Hayes said, explaining how an inspector may not even know about the device. "Not necessarily, because it looks like the regular card reader, except for an embossing of Made In Japan on it."
Skimmers usually emit a Bluetooth signal showing letters and numbers separated by colons.
Hayes said your cellphone could help you detect one.
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"Go to settings, turn on the Bluetooth signal," Hayes explained. "(It shows) all the available Bluetooth signals. Right now, there's no generic Mac address being emitted, so I'm pretty comfortable there's not a skimming device at this gas station."
Gas station owners say criminals have posted fake security tape on pumps in the past. Now, they're watching out for the new skimmers.
Agents warn checking your Bluetooth isn't a fail safe way to protect yourself because many criminals are smart enough to change the signal name to something that looks legitimate.
If you do spot a signal that seems suspicious, agents say to go inside to pay and ask the clerk to check it out.