India, Nov. 5 -- What happened

Hackers have repeatedly broken into the remote-control systems of supermarket refrigerators and freezers across Europe since October, forcing units into prolonged "defrost mode" so they overheated. Some units reportedly reached temperatures as high as 50 degrees Celsius, with isolated reports of 80 degrees Celsius. The result was spoiled food, a few small fires caused by the heat, and losses running into millions of euros.

The attacks have come in two major waves. On October 11-12, around 700 of France's 10,000 supermarkets were hit, including Carrefour, Monoprix, Intermarche, Netto and Cooperative U. Attackers extended normal one-hour defrost cycles to six to eight hours and delayed alarms, giving staff l...