Hackers remotely manipulated refrigeration systems, raising temperatures to as high as 50°C in some stores.
The disruption caused food to spoil and reportedly triggered fires in several locations.
Intermarché confirmed that around 150 of its stores were affected, while Carrefour reported disruption at 80 supermarkets.
Nearly 100 Coopérative U outlets were also targeted, alongside approximately 5% of Monoprix stores.
Affected retailers have been forced to dispose of fresh and frozen products to avoid health risks.
Intermarché estimates that the financial losses could reach tens of millions of euros nationwide, with some stores expected to take several days to return to normal operations.
Authorities launch investigation
The Paris prosecutor’s office has opened an investigation, while Prime Minister Sébastien Lecornu has instructed France’s national cybersecurity agency, ANSSI, to examine the attack.
Investigators have identified a security vulnerability involving refrigeration control systems supplied by Danish manufacturer Danfoss.
The company acknowledged that affected equipment was running outdated software.
French authorities are also coordinating with European counterparts amid concerns that similar systems in other countries could be vulnerable.
Dining and Cooking