Investigators hunt hackers who heated French supermarket fridges, sparking fires and spiling food

French investigators on Tuesday were hunting the hackers who seized control of cooling units at hundreds of supermarkets in a cyberattack that underlined the vulnerabilities of connected systems, with no group publicly claiming responsibility.

The cyberattack, which manually overrode the temperatures at fridges in supermarket groups including Carrefour, Monoprix, Intermarche and Cooperative U, appears to have been easy to pull off, three cyber experts told Reuters.

Staff at some Paris supermarkets threw boxes full of perished meat and frozen goods into giant trash containers on Tuesday. At least 350 supermarkets — a small fraction of the total number in France — were caught up in the strike.

Prime Minister Sebastien Lecornu instructed France’s National Cybersecurity Agency (ANSSI) to investigate, a person in his office said.

France was coordinating with European counterparts because other countries could also be affected, the person said, adding that authorities were assessing whether other French companies were at risk.

Cooperative U CEO Dominique Schelcher said 80 of its stores — out of an overall group total of 2,000 — were affected.

He said he could not precisely quantify the financial impact, but added that in a smaller store it would be several tens of thousands of euros, while in a bigger hypermarket the impact could be up to €200,000 ($223,480).

There was no immediate estimate of industry-wide losses, but Intermarche CEO Thierry Cotillard told BFM TV the “unprecedented” attack would represent losses amounting to “tens of millions of euros nationwide in a single day.”

Christel Delberghe, director general at European retail association Eurocommerce, said, “This incident underlines the importance of resilience across the entire supply chain.”

Supermarket cold aisles are typically run by control panels that manage an entire store’s fridges and freezers and can be accessed over the internet, which lets maintenance companies adjust them from anywhere.

The affected fridges relied on software by Danish firm Danfoss.

On Monday, Danfoss said many of the affected units had “reached end of life and no longer receive software or security updates” or were “running outdated firmware.” It said it had “advised customers to keep supported systems updated with the latest firmware and to migrate legacy systems to current-generation solutions.”

The company declined further on Tuesday.

The serious vulnerabilities present in older versions of Danfoss’ firmware have been known for months.

On August 9, cybersecurity firm Claroty detailed weaknesses — since patched — in the Danfoss AK-SM 800A controller that could have allowed intruders to bypass authentication and run code on compromised devices.

Although the precise mechanism by which attackers compromised the refrigerators has not been publicly disclosed, cybersecurity experts said all signs pointed to a basic stunt enabled both by the failure to adopt Danfoss’ updates and by exposing device interfaces to the internet.

“This is basic cyber hygiene,” said Ken Munro, a partner at the British cybersecurity firm Pen Test Partners. “Get it wrong and you get a smelly mess of defrosted food.”

He said the well-known vulnerabilities meant the attackers were essentially pushing at an open door, something that meant the hack could easily be “kids messing around.”

“If this was a nation state, why affect only a subset of French fridges? There are plenty of other nations with fridges on the internet,” he said. “No ransom or demand suggests a lack of appreciation of the potential commercial losses that the fridge owners may experience.”

Plenty of fridges remain reachable via the internet. Using the internet scanning service Shodan, Reuters found at least 4,500 Danfoss interfaces still viewable on Tuesday.

Reuters could not independently establish how many of them were running vulnerable software, but French internet scanning company Onyphe said only a small minority of the devices appeared to be running the latest version of the software.

Outdated and vulnerable versions were “still widely represented among publicly accessible interfaces,” Onyphe said.