Refrigerators and freezers went down overnight into Monday at more than 12 ICA and Coop grocery stores across Sweden, with at least one store reporting that its cooling systems had been hacked and set to 50 degrees Celsius, or 122 Fahrenheit.

ICA described the event as an incident that affected refrigeration and freezer systems at a limited number of stores, adding that the affected locations connect to the internet outside the company's central network.

The episode highlights an exposure that is becoming familiar in grocery retail: store refrigeration sits at the heart of the cold chain that keeps perishable food within safe temperature ranges, and when freezers fail or are tampered with for even a few hours, entire sections of stock have to be written off.

Five ICA stores in southern Sweden hit

The five affected ICA stores in southern Sweden are Ica Kvantum Sjöbo, Ica Kvantum Tomelilla, Ica Nära Böda, Ica Supermarket Brösarp and Ica Nära Sankt Olof. Ica Baronen in Stockholm was also hit.

Ica Kvantum Sjöbo wrote on Facebook that its cooling and freezer systems had been hacked and set to 50 degrees.

Coop press officer Carlos Cancino said six Coop stores in central Sweden were affected.

At Ica Nära Sankt Olof, all ice cream freezers and all freezer cabinets were hit, owner Camilla Nilsson said. Chilled goods that have stayed chilled are being sold at half price, while everything else is being discarded.

Brösarp outage began around 3 a.m.

Mattias Liljegren, who runs Ica Supermarket Brösarp, said the systems were knocked out at around 3 a.m. local time and that staff detected the problem. He believed it was the same thing that happened in France. Brösarp has thrown out all of its ice cream and is still sorting through the rest of its stock.

Both stores have had their systems restored, and Sankt Olof has barred its cooling equipment from the internet. ICA has sent support to the impacted stores. Cybersecurity expert Nicklas Keijser has called on stores to disconnect their fridges and freezers from the internet.

Swedish incidents follow October attacks in France

The Swedish failures came weeks after hackers took control of cooling units at hundreds of French supermarkets in October, French police said. The French attack resulted in food losses and fires. French attackers appear to have taken over the defrost function and run it 24/7 at 50 degrees, Cryptopolitan reported.

Controllers such as the AK-SM800 and AK-SC355 centrally manage temperatures and defrost cycles for a store's refrigeration cabinets, so taking over the defrost function can affect an entire store's cold storage at once.

Les Mousquetaires, which owns Intermarché, said fridges at about 150 of its stores stayed at 50 degrees for six hours, and the group disposed of all the affected food. Carrefour said 80 of its supermarkets were attacked, though most of its roughly 6,000 outlets were untouched. Monoprix said 5% of its roughly 490 stores in France were affected.

Danish manufacturer Danfoss, which produces the hijacked AK-SM800 and AK-SC355 controllers, said the affected units were running obsolete firmware, much of it legacy systems that no longer receive security updates. A source close to Prime Minister Sebastien Lecornu said the French cybersecurity agency ANSSI uncovered a vulnerability in Danfoss software.

Threat analyst Felix Aime said Spain, Portugal, Poland, Germany and Belgium were also hit by attacks. Together with France and Sweden, that puts reported incidents in seven European countries, making internet-connected supermarket refrigeration equipment a regionwide concern for grocery chains.

No equipment maker has been identified for the Swedish stores, and no link has been made to the French attacks. How the Swedish systems were accessed, which equipment was involved, and whether investigators establish a connection to the October attacks in France are the questions to watch as the story develops.