Hackers could already be inside American utilities, cyber experts warn of 'Trojan Horse' threat

The cyberattack targeting French supermarket freezers and causing millions of dollars in losses last week should be an ominous warning to American businesses, cybersecurity experts told Fox News Digital.

Unknown hackers took over the refrigeration in hundreds of supermarkets across France, raising temperatures above 100 degrees Fahrenheit overnight, causing massive spoilage.

It could happen here, and it isn't just grocery stores that need to be on guard, John Walsh, senior vice president at the Germany-based software company IGEL, told Fox News Digital.

"Think about if we don't have water for seven days, or if they attack freezers and we don't have food," Walsh said.

"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 companies who build and deploy critical infrastructure — such as Siemens and Rockwell — to bolster their operational security.

FRENCH SUPERMARKETS FACE MILLIONS IN LOSSES AFTER CYBERATTACK HITS REFRIGERATORS NATIONWIDE As was the case in France, where Danish commercial refrigeration system manufacturer Danfoss highlighted that many of its affected fridges were legacy systems that no longer receive updates, much of the U.S.’s critical infrastructure is also in need of retooling, Walsh said.

"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." FBI OVERHAULS TECH BACKBONE TO COUNTER AI THREATS FROM FOREIGN ADVERSARIES, REDUCE RESPONSE TIMES, PATEL SAYS Decision makers at the companies Walsh works with don’t want to go through the hassle of taking key systems offline in order to upgrade and secure them further, operating under a "if it's not broken, don't fix it" mindset," he said.

But 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.

BILL GATES SOUNDS ALARM ON AI-POWERED CYBERATTACKS, WARNS OF 'NEGATIVE SURPRISES' WITHIN A YEAR "One of the big things we have to consider is that we're moving from a thought process of security to resilience," Walsh said.

As AI helps hackers become more sophisticated, it’s no longer wise to attempt to completely shut them out of key systems, Walsh said.

System operators are better off assuming the hackers are already there.