Companies are touting the newest generation of credit cards, where data are transmitted instantly by radio waves.
There's no need to swipe or sign to make a purchase.
They may make shopping faster and easier, but some computer experts warn these new cards -- now being issued by the millions -- may also make identity theft easier, too.
A pair of computer scientists at the University of Massachusetts recently went online and bought one of the radio-wave card readers the stores use.
The duo collected 20 cards from colleagues and friends, and with one beep they pulled up the name, card number and expiration date on all of them.
"If you are holding your card, and [a] thief comes behind you for instance and gets close enough, then your card will be read," said Kevin Fu, one of the researchers.
They call it the "Johnny Carson attack."
Just like the late comic who jokingly said he could tell the contents of an envelope by holding it to his forehead, the scientists were able to glean personal information even from a new credit card still sealed in its original envelope.
In other words, a thief could read the information on your card even if it was in your wallet, if they had the right equipment.
"A person could take this equipment and put it into a backpack and go to a crowded area and basically start collecting credit card numbers," said Avi Rubin, a professor of computer science at Johns Hopkins University.
American Express told "Good Morning America" that its cards were protected by the "highest industry level of security."
Chase said the read range on its cards was "less than 2 inches."
And MasterCard argued that the study "does not take into account the full range of security features" built into the system.
Credit card companies offer customers a 100 percent "zero liability" protection. They say customers will have no financial obligation from any fraudulent or unauthorized activity on their account.
Ultimately, however, the costs the credit companies incur protecting you -- said to be billions of dollars a year -- are passed right back to you in the form of higher interest rates, annual fees, and other card costs.