Criminals steal the information by installing a small device called a skimmer inside the pump. It copies your credit or debit card information when you pay.
The Secret Service found 59 skimmers at 85 locations in 21 states over the weekend.
When drivers pay for their fuel, the devices copy their credit card numbers. That data is then used to print fake credit cards, which can be used to make fraudulent purchases without the owner's knowledge.
"They're monetizing the stolen payment card data in multiple ways and the easiest way is they'll take the stolen payment card number and will re-encode a gift card or credit card and then they will use that to buy electronics, gift cards, stuff that they can fence on grey market, the black market or the open market," Matthew O'Neill Assistant to the Special Agent in Charge of the Criminal Investigative Division explained to ABC News.
A high-level skimmer can send credit card information through a Bluetooth device, so criminals don't have to return to the scene to get the skimmer back.
"The new skimmers have Bluetooth technology where you don't need to go back and take the skimmer out, you can wireless access the information from a truck nearby and collect information and leave the Bluetooth in there the whole time," said Canh Tran, a cyber security expert with Rippleshot, a Chicago-based fraud analytics firm.
Thieves gained access to the pumps by buying commercial keys online.
Tran said that while fraudsters become more tech savvy, there are steps consumers can take to avoid being a victim. Paying cash is the safest route, but consumers should also look for a security tape on the pump. If it's been tampered, there is likely a skimmer inside.
Tran said thieves usually put a skimmer in only one pump at a gas station, picking the one furthest away from the clerk.
"When you go to the pump, make sure whatever pump you're picking, it has a clear line of sight where the convenience clerk presides," said Tran.
According to Tran, gas stations have become prime targets because the industry has until 2020 to become EMV chip compliant. The chip protects cardholder data. The law required merchants to become compliant in 2015.
"It kind of scares me honestly, it makes me want to start using cash even though I won't know how much it will take to fill up my car, I'd rather be safe than sorry," said Morgan Miller, a gas station customer.
"Our data is not safe, that is just the facts of the world we live in, said C.G. McDaniel, another customer."