High street technology retailer Dixons Carphone have revealed that they were the victim of a cyber attack, with 5.9 million customer bank card details and 1.2 million personal data records hacked.
While 5.8 million of the payment cards targeted were protected by chip and pin, around 105,000 non-EU cards without chip and pin protection were compromised, according to the group.
Card companies had been notified, according to Dixons Carphone but the group suggests that there was no evidence of fraud on the cards as a result of the incident.
It added that its investigation had also found that hackers accessed non-financial personal data - such as name, address or email details - for 1.2 million customer records.
No evidence of fraud yet
The group is contacting all those affected, but sought to assure customers it had no evidence that this had resulted in fraud at this stage.
It said it had called in cyber experts and added extra security to its systems following the breach, while also since calling in the police and relevant authorities.
TalkTalk were fined £400,000 for failing to keep their customers' data secure (Photo: Shutterstock)
Dixons Carphone chief executive Alex Baldock admitted the group had "fallen short" of its responsibility to protect customer data.
He said: "We are extremely disappointed and sorry for any upset this may cause.
"The protection of our data has to be at the heart of our business, and we've fallen short here.
"We've taken action to close off this unauthorised access and, though we have currently no evidence of fraud as a result of these incidents, we are taking this extremely seriously."
Dixons said the hack occurred in one of the processing systems of Currys PC World and Dixons Travel stores.
It said the data accessed did not contain Pin codes, card verification values (CVV) or any authentication data allowing cardholder identification or a purchase to be made.
The group added it did not believe the personal data accessed had left the group's systems, but was advising those affected on protective steps they should take.
It comes after telecoms firm TalkTalk was hit by a major cyber attack in October 2015, which saw the personal data of nearly 160,000 people accessed by hackers and left the firm facing a record £400,000 fine for security failings.