Hackers May Already Be Inside America's Utilities, Experts Warn of a 'Trojan Horse' Threat

The cyberattack on French supermarket freezers should be an ominous warning to the United States, cybersecurity experts say. Their fear is that hackers may already be hidden inside America's power, water and other critical systems like a Trojan horse, simply waiting to be activated.

Last week, unknown hackers took over the refrigeration in hundreds of supermarkets across France, raising temperatures above 100 degrees Fahrenheit overnight and causing massive spoilage and millions of dollars in losses. Experts say the same thing could happen in America, and grocery stores are not the only ones that need to be on guard.

'Think about if we don't have water for seven days, or if they attack freezers and we don't have food,' said John Walsh, senior vice president and field CTO for government and critical industries at the Germany-based software company IGEL. 'That's a tough situation for people to live through, and it could create a lot of economic and social unrest. We're seeing that we're vulnerable and that attacks are taking systems down.'

At IGEL, Walsh works with governments and with companies that build and deploy critical infrastructure — such as Siemens and Rockwell — to bolster their operational security.

In France, Danish commercial refrigeration manufacturer Danfoss highlighted that many of the affected fridges were legacy systems that no longer receive updates. Much of the United States' critical infrastructure is likewise in need of retooling, Walsh said.

A photograph from October 12 at an Intermarché supermarket in Névez, western France — a woman walking past empty fresh-food refrigerators — illustrates the damage. The attack affected the Intermarché and Cooperative U chains and caused their refrigerators to defrost.

'A primary obstacle in operational technology environments — whether in food manufacturing, pharmaceuticals, oil, or utilities — is that facilities operate assets that are 15 to 20 years old,' Walsh said. 'These systems are expensive, fragile, and essential to ongoing operations.'

Mindset is another problem. Decision makers at such companies do not want the hassle of taking key systems offline in order to upgrade and secure them further, operating under an 'if it's not broken, don't fix it' approach, he said.

Yet critical infrastructure, like almost every aspect of American society, is becoming increasingly integrated with technology and embedded into digital infrastructure, forcing cybersecurity firms to fundamentally shift strategies.

Walsh argues the focus must move from security to resilience. As AI helps hackers become more sophisticated, it is no longer wise to try to shut them out completely; operators are better off assuming the hackers are already there. 'Security is kind of like, "I feel I can trust that things are okay." Resilience is where you make the assumption the attacker is present — where, when the attacker is present, you control the blast radius,' he said.

His starkest warning concerns a so-called Trojan horse, which could already be inside America's electrical grid and other critical infrastructure, waiting for the adversary to activate it. Adversaries have demonstrated taking systems down, he said, which is to some degree practising and honing their skills and methodologies against real targets while sending a message.

Policy experts are grappling with recommendations for lawmakers, given how much of everyday life is connected to the internet. 'I am shocked that appliances have access to the internet,' Amy Kremer, the chair of Humans First, said. 'I understand the convenience, but at the same time, you are going to have potential problems with it. That should be a concern to all Americans — not just appliances, but things like your Nest thermostat and other devices in your house that could be hacked into.'

America's critical infrastructure is indeed vulnerable to these threats, Walsh said, citing a 2026 coordinated cyberattack on Minnesota's water systems. 'Think about if you were to try to disrupt the U.S. economy or begin to do terrorism-type activities. What would you do? You'd go after water and wastewater. You'd go after the food supply. Exactly what occurred here, but at a larger scale,' he said.

He warned this could be just the beginning, pointing to a pattern across the U.S., France and the UK in which a potential geopolitical adversary appears to be practising and demonstrating its craft in different locations ahead of bolder attacks. 'We're definitely more vulnerable, they're definitely targeting us, and citizens, government, and the international community need to get governance in place to push industries to implement these protections,' he said. Danfoss was contacted for further comment.