A cyber-attack on supermarket freezer temperature control systems across several grocery chains in France earlier this month has authorities speculating who was responsible, reports The Guardian.

In the middle of the night on October 11, hackers managed to remotely override the temperature settings on thousands of freezers, fridges and chiller cabinets pushing them from as low as -16.6F to well over 100F, causing the food to cook and spoil. In some stores, the rapid temperature rise sparked fires, triggering sprinklers and causing water damage.

As supermarket staff worked late to restock shelves after removing tons of spoiled food, it soon became clear that up to 700 stores – including those from the Intermarché, Coopérative U, Carrefour, Leclerc and Monoprix chains along with a number of smaller independent shops – had been victims of a widespread cyber-attack.

The Guardian says the Paris public prosecutor’s office immediately opened an investigation into the latest in a series of cyber-attacks that have made France the most hacked country in Europe, while cybersecurity experts speculated that it was either a group of young pranksters, or a foreign power.

The hackers targeted fridge and freezer controllers supplied by the Danish company Danfoss, which are connected to the internet to allow remote maintenance and alerts for system failures. Danfoss said it had identified some security flaws in 2025 and had “long recommended” that customers install updates or replace obsolete unsupported systems. The affected refrigeration units were “running outdated firmware,” it said. In the days following the first wave of attacks, France’s cyber-attack alert center ANSSI confirmed supermarkets using controllers from two other companies were also targeted.

This latest attack comes on the heels of a similar incident in the U.S. in August, when connected fridges and freezers at a dozen military commissaries went into unscheduled defrost cycles overnight causing massive food loss.

The Guardian cites cybersecurity and risk management company Upguard's assessment that France is the most heavily pirated country in Europe by the volume of records exposed by hackers.