They turned cold storage into an oven.

After closing on Sunday night, the fridges in hundreds of French supermarkets began heating up without explanation. Someone had reached into the refrigeration controllers at Intermarché, Coopérative U, Leclerc, Carrefour and Monoprix stores and forced a continuous defrost cycle. Display cases climbed toward 50 degrees Celsius (122 Fahrenheit).

Food spoiled. A few units caught fire. Piles of French cheese were (presumably) ruined.

By Monday the Paris prosecutor had an investigation open and France’s National Cybersecurity Agency (ANSSI) was warning its neighbors that the same software runs in their stores as well.

Why would anyone hack a fridge? And why am I writing about it? The answer to both questions is this: modern society is built on critical infrastructure that is invisible until it breaks. Supply chains, energy grids and sewage systems make our existence possible. A couple of lines of malicious code can cause outsized effects.

We left the door to the china shop wide open and the world is full of bulls.

At least one chain said the attack came through a contractor that manages refrigeration inside its stores. In August, researchers at Claroty published a teardown of the Danfoss AK-SM 800A, a controller that coordinates supermarket cooling. They found a hidden login bypass and counted about 2,700 of these management panels sitting open on the public internet. Danfoss fixed the flaws in August 2025. A patch only works when someone installs it.

Guess what. Thousands of panels were sitting exposed a year later. We’ve seen this before.

In January 2024, a resident of Muleshoe, Texas noticed the town water tower overflowing. Hackers had brute-forced the password on a vendor-run control panel and reset the pumps. The group called itself Cyber Army of Russia Reborn. Mandiant traced its accounts to Sandworm, the Russian military intelligence (GRU) unit behind NotPetya, though US officials have not confirmed the link.

Two months before that, an Iranian-linked crew calling itself CyberAv3ngers accessed a booster station at the Municipal Water Authority of Aliquippa, Pennsylvania through an internet-facing Unitronics controller. The password was the factory default, 1111. None of this required National Security Agency (NSA) tradecraft. It required knowing where to look in order to infiltrate and exploit the things that society needs but never thinks about.

Go back to May 2017 and the WannaCry worm shut down a third of England’s National Health Service (NHS) hospital trusts and cancelled about 19,000 appointments. The National Audit Office found that every infected NHS body was running unpatched or unsupported Windows. The fix had been available for two months. The infected trusts did not apply it.

The exploit in all cases was cheap and easy. A controller someone forgot was connected to the internet or software that didn’t get updated. The cost was high, but in reality it could be much worse.

Consider the other infrastructure we never think about. Sewage lift stations run on the same programmable logic controllers (PLCs) as water plants, the small industrial computers that switch pumps on and off, and the Cybersecurity and Infrastructure Security Agency (CISA) says its Unitronics advice applies to every PLC reachable from the internet. Do you think they’ve all been updated?

Security cameras are a lost cause. Sites like Insecam have streamed unsecured camera feeds from around the world for over a decade. Then there are cars. In 2015 Wired put a reporter on a St. Louis highway while two researchers killed his Jeep’s transmission from a laptop miles away, through the entertainment system. Now, over ten years later, every new car is basically an internet-connected computer that happens to drive.

Modern life is a network, and a network is made of chokepoints. The moment a convenience works, it goes invisible. The moment it goes invisible, we stop checking on it. We forget the patch. We don’t update the password. We leave the door to our most valuable systems wide open.

The French hack cost grocers millions and a few days of empty shelves. So why do you hack a fridge? Because no one is watching and everyone needs it.