Cyber security expert Christopher Evans said ATM "skimming" -- thieves using ATMs to defraud bank customers -- is a growing problem.
He says an ATM user may walk up to the machine and not see that it has been tampered with.
"They'll put readers over the existing face of the ATM (or) hide cameras off to the side so they can capture your pin card," he said. "They've gotten very smart on how to capture that information."
According to the U.S. Secret Service, in 2008, ATM skimming was a billion-dollar industry.
This year, Verizon Data Breach Report said it was a $21 billion industry.
One out of every three instances of data fraud is an ATM attack.
The No. 1 thing to do to protect yourself, Evans said, is to shield your pin number.
"Use two hands when you're putting in your pin number. Use one hand to put in the pin number and use your other to cover it," said Evans.
He also advises people to just use ATM machines inside banks or choose stores that allow cash back with your purchase. He says it's harder for cyber thieves to attach skimming devices there.
“If you see anything sticking out from the front of the ATM, give it a little pull. If it comes off, it's a skimming device," he said.
Drive-up ATMs are the worst to go to, Evans said, simply because said cyber thieves will target these on the weekends when the banks are closed, and the thieves know banks don't reopen until Monday.