Co-op narrowly averted being locked out of its computer systems during the cyber attack that saw customer data stolen and store shelves left bare, the hackers who claim responsibility have told the BBC.
The revelation could help explain why Co-op has started to recover more quickly than fellow retailer M&S, which had its systems more comprehensively compromised, and is still unable to carry out online orders.
Hackers who have claimed responsibility for both attacks told the BBC they tried to infect Co-op with malicious software known as ransomware – but failed when the firm discovered the attack in action.
Both Co-op and M&S declined to comment.
The gang, using the cyber crime service DragonForce, sent the BBC a long, offensive rant about their attack.
In it, they expressed anger that Co-op’s IT team made the decision to take computer services offline, preventing the criminals from continuing their hack.
“Co-op’s network never ever suffered ransomware. They yanked their own plug – tanking sales, burning logistics, and torching shareholder value,” the criminals said.
Cyber experts like Jen Ellis from the Ransomware Task Force said the response from Co-op was sensible.
“Co-op seems to have opted for self-imposed immediate-term disruption as a means of avoiding criminal-imposed, longer-term disruption. It seems to have been a good call for them in this instance,” she said.
Ms Ellis said these kinds of crisis decisions are often taken quickly when hackers have breached a network and can be extremely difficult.
Speaking exclusively to the BBC, the criminals claimed to have breached Co-op’s computer systems long before they were discovered.
“We spent a while seated in their network,” they boasted.
They stole a large amount of private customer data and were planning to infect the company with ransomware, but were detected.
Ransomware is a kind of attack where hackers scramble computer systems and demand payment from victims in exchange for handing back control.
It would also have made the restoration of Co-op’s systems more complex, time-consuming and expensive – exactly the problems M&S appears to be wrestling with