Computers at Dairy Queen locations, and one Orange Julius smoothie stores, were infected by the malicious software, Backoff, which has been targeting retailers since it first surfaced a year ago, International Dairy Queen said late on Thursday.
The Edina, Minnesota-based company is a subsidiary of Berkshire Hathaway (BRK-A) (BRK-B).
"We are committed to working with and supporting our affected DQ and Orange Julius franchise owners to address this incident," John Gainor, chief executive of International Dairy Queen, said in a statement.
The malware infected computers at 395 of its more than 4,500 U.S. locations, exposing the names, numbers and expiration dates of customer payment cards, the statement said. There is no indication that other personal information, including card PINs, social security numbers or email addresses were stolen, it said.
International Dairy Queen said it is offering free identity repair services for one year to customers in the United States who made purchases at any of the effected restaurants.
Stores in four states, Rhode Island, Vermont, Hawaii and Louisiana, didn't appear to be impacted by the breach, the company said.
The U.S. government has released reports on several types of malicious software that cyber criminals have used to steal payment cards in the wake of last year's breach on Target (TGT), which resulted in the theft of some 40 million card numbers.
Backoff, first identified in October 2013, is capable of scraping computer memory for track data and logging keystrokes, the U.S. Department Of Homeland Security warned retailers in July.
Why Your Bank Thinks Someone Stole Your Credit Card
Dairy Queen Latest Retailer to Suffer Customer Card Hack
One reason why Marquis' gas purchases might have triggered a fraud lockdown? Filling their tank is a common first move for credit card thieves.
"Some of the things they look at are small-dollar transactions at gas stations, followed by an attempt to make a larger purchase," explains Adam Levin of Identity Theft 911.
The idea is that thieves want to confirm that the card actually works before going on a buying spree, so they'll make a small purchase that wouldn't catch the attention of the cardholder. Popular methods include buying gas or making a small donation to charity, so banks have started scrutinizing those transactions.
Of course, it's not a simple matter of buying gas or giving to charity -- if those tasks triggered alerts constantly, no one would do either with a credit card. But Levin points to another possible explanation: Purchases made in a high-crime area are going to be held to a higher standard by the bank.
"It's almost a form of redlining," he says. "If there are certain [neighborhoods] where they've experienced an enormous amount of fraud, then anytime they see a transaction in the neighborhood, it sends an alert."
(Indeed, Erin tells me that one of the gas purchases that triggered an alert took place in a rough part of Detroit, which she visited specifically for the cheap gas.)
People who steal credit cards and credit card numbers usually aren't doing it so they can outfit their home with electronics and appliances. They don't want the actual products they're fraudulently buying; they're just in it to make money. So banks are always on the lookout for purchases of items that can easily be re-sold.
"Anytime a product can be turned around quickly for cash value, those are going to be the items that you would probably assume that, if you were a thief, you would want to get to first," says Karisse Hendrick of the Merchant Risk Council, which helps online merchants cut down on fraud. Levin says electronics are common choices for fraudsters, as are precious metals and jewelry.
Many thieves don't want to go through the rigmarole of buying laptops and jewelry, then selling them online or at pawnshops. They'd much prefer to just turn your stolen card directly into cold, hard cash.
There are a few ways that they can do that, and all of them will raise red flags at your bank or credit union. Using a credit card to buy a pricey gift card or load a bunch of money on a prepaid debit card is a fast way to attract the suspicions of your credit card issuer. Levin adds that some identity thieves also use stolen or cloned credit cards to buy chips at a casino, which they can then cash out (or, if they're feeling lucky, gamble away).
When assessing whether a purchase might be fraudulent, banks aren't just looking at what you bought and where you bought it. They're also asking if it's something you usually buy.
"The issuers know the buying patterns of a cardholder," says Hendrick. "They know the typical dollar amount of transaction and the type of purchase they put on a credit card."
Your bank sees a fairly high percentage of your purchases, so it knows if one is out of character for you. A thrifty individual who suddenly drops $500 on designer clothes should expect to get a call -- or have to make one when the bank flags the transaction. If you rarely travel and your card is suddenly used to purchase a flight to Europe, that's going to raise some red flags.
Speaking of Europe, the other big factor in banks' risk equations is whether you're making a purchase in a new area. I bought a computer just days after moving from Boston to New York, and had to confirm to the bank that I was indeed trying to make the purchase. Levin likewise says that making purchases in two different cities over a short period of time raises suspicions.
"I go from New York to California a lot, and invariably someone will call me [from the bank], " he says. Since one person can't go shopping in New York and California at the same time, any time a bank sees multiple purchases in multiple locations in a short period, it's going to be suspicious.