Restaurant chain P.F. Chang's China Bistro says the theft of credit and debit card information from some of its restaurants earlier this year was "part of a highly sophisticated criminal operation."
But the chain, which only discovered the breach after a large batch of card numbers were offered on an Internet forum, said it's still working with the U.S. Secret Service and forensic experts to determine exactly what happened.
"We continue to make progress in our investigation into the recent security compromise that affected P.F. Chang's," said Rick Federico, CEO of PF Chang's, in a statement posted Tuesday on the company's website. "We will continue sharing important details once they have been confirmed by a team of third-party forensic experts."
The statement was the first update issued by the company in three weeks and didn't add much additional information to what was already known: that an attack apparently hit the point-of-sale systems in the company's restaurants and sucked up card numbers used between March and May of this year.
After the breach was discovered June 10, the restaurant switched to manual card imprinters in its restaurants, which were later processed via an encryption-enabled terminal that works on a dial-up fax line. Additional terminals have recently been delivered to restaurants to decrease the reliance on the hand-operated imprinters, the company said.
The breach was the latest in a string of attacks against point-of-sale systems at major U.S. retailers. In late 2013 around 70 million customer records were compromised in an attack on Target stories and criminals also targeted Nieman Marcus.
In those attacks, payment card details were grabbed by malicious software after cards were swiped. P.F. Chang's has yet to disclose specific details about how attackers gained access to card information in its system.
A recent survey determined such breaches are speeding adoption of chip-based payment cards in the U.S.
Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is email@example.com