Hackers are going after the machines that keep food and blood products and chemicals cold. The FBI and the nation's cyber defense agency warned that attackers are actively targeting industrial refrigeration and cold-chain monitors used in grocery warehouses and hospitals and chemical plants and transport.

The joint alert with health agriculture and transportation partners says groups that rely on those systems should assume they could be next.

How the attacks work

Many controllers sit on the public internet with weak or default passwords. Attackers exploit that exposure along with unpatched flaws and authentication bypasses to seize the panels that set temperatures and run defrost cycles.

Once inside they can force units into continuous heating or defrost mode. That can spoil inventory shorten equipment life hide real temperatures from operators and in some cases create fire hazards.

A threat already seen overseas

Recent incidents in Europe showed what that looks like in practice. Controllers at hundreds of French stores were hijacked. A later wave hit more than 100 shops across several countries. Blood-storage sites also reported tampered settings after a vendor breach.

U.S. agencies urge operators to pull refrigeration controllers off the open internet isolate them from office networks change default credentials apply updates and set hard temperature limits so a compromised panel cannot run gear outside a safe range.

Remote access when it is truly needed should sit behind updated edge devices rather than a bare login on the public web. Every cold chain that skips those steps is an easier target.