The hack is believed to have been the result of an internal leak, with data copied onto a portable storage device and taken out of Morrisons' Bradford headquarters. The data had details of staff from director level to the shop floor, was also sent anonymously to a local paper in Yorkshire, the Telegraph & Argus, by a "concerned Morrisons shopper.”
Morrisons announced a massive profits warning on Thursday, which sent shares diving 12 per cent and the attack came hours after the chief executive, Dalton Philips, boasted that new IT systems would help to turn around Morrisons' performance. It said it was now "urgently reviewing our internal data security measures," and was working with UK banks and credit check service Experian to help colleagues secure their bank accounts.