Hackers have sparked fires and floods in French supermarkets after targeting temperature gauges in internet-connected refrigerators.

The attackers remotely took over refrigeration systems, resetting target temperatures to 50ºC, leading to fires as well as floods from sprinkler systems, destroying fresh and frozen food.

The hack hit hundreds of supermarkets, including Intermarche, Carrefour, Cooperative, and Monoprix, according to reports. Authorities said an investigation had been started into the “large-scale cyberattack” that targeted the country’s food supply.

“Targeting equipment essential to the preservation of fresh products and to the food supply of the French people is extremely serious and is unprecedented. It is unacceptable,” CEO of Cooperative U, Dominique Schelcher, wrote on X.

Dutch supermarkets also reported security issues, with some digital systems taken offline at the Albert Heijn chain, while reports suggest supermarkets across Europe may also be affected.

What happened?

The attack began overnight, with temperatures slowly rising over the course of several hours. The hackers appear to have targeted store fridges and freezers via control panels that are accessible via the internet in order to be adjusted and maintained, Reuters reported.

“The attack was probably launched at about 11.00pm but we didn’t become aware of it until 4.00am, when our delivery driver saw that the stock room was flooded,” said Charles Dezon, manager of the Intermarché supermarket in Gradignan (Gironde), in a report from Le Monde. “The temperature had risen to 50ºC in the cold room and activated the automatic sprinkler system.”

Reports suggest the hackers forced the equipment into a constant defrost cycle, leading to overheating.

Known flaw, legacy systems

A source told AFP that the hacked systems appeared to be largely made up of refrigeration control systems from Danfoss, a Danish equipment manufacturer. Danfoss told that news agency that the attack targeted “legacy” systems that no longer received software or security updates, notably the AK-SM800 and AK-SC355 regulator systems that had “outdated firmware”.

Danfoss added, in a statement sent to Reuters, that it had “long advised customers to keep supported systems updated with the latest firmware and to migrate legacy systems to current-generation solutions”.

Indeed, the attacks come two months after Claroty’s Team82 spotted multiple vulnerabilities in Danfoss’s AK-SM 800A platform. The vulnerabilities were disclosed to Danfoss, which issued fresh firmware to patch the flaws; however, that appears to not have covered the older version, as it was no longer supported by the company.

At the time, Claroty noted: “A compromised supervisory controller grants an attacker the ability to physically manipulate refrigeration systems and silently spoil the contents.”

What’s next?

Stores are working to clean up after the incident, with staff spotted chucking spoiled food into bins, but full recovery will likely take much longer — and be expensive. Intermarche CEO Thierry Cotillard told local television that the losses were likely to top “tens ​of millions of euros nationwide in a single day.” In the UK, last year’s ransomware attacks cost M&S and Co-op up to £440 million.

“The impact on French supermarkets will likely last months,” said James Neilson, SVP of Global at OPSWAT. “More than a year on, M&S and Co-op are still feeling the financial and organisational effects of their attacks.”

He added: “Refrigeration technicians have to inspect and restore systems site by site, and retailers must reassure customers that what’s back on the shelves is safe.”

It’s as yet unclear who committed the attacks, but they come a month after French President Emmanual Macron warned that critical national infrastructure needed to be protected from Russian cyber attacks.

Muhammad Yahya Patel, vCISO and cybersecurity advisor for EMEA at Huntress, noted that the security industry has long been warning about attacks on operational infrastructure, saying that these refrigeration systems had been “weaponised”. He added: “The food retail sector across Europe should be treating this as a signal that they are being actively targeted.”