Industrial refrigeration controller hacks and what small businesses can do

Did you know that a single unauthorised change to a refrigeration controller can raise the internal temperature by up to 15°C in minutes, turning a fridge into a furnace? We see this more often than you might think. What happened in the workshop? We received a frantic call at 08:45 from the owner of a local bakery. Their walk‑in fridge, which holds pastry dough and perishable fillings, was displaying a steady rise in temperature. The digital read‑out showed 30°C – well above the safe 4°C range – and the alarm was silent. By the time we arrived, the baker had already discarded half a day's worth of stock, costing roughly £1,200. Our initial diagnosis: the fridge’s controller had been accessed remotely and the set‑point had been switched from “cool” to “heat”. The device was reachable from the internet because the bakery’s router had an open port for remote monitoring that was never secured. Why are refrigeration controllers a target? Industrial and commercial refrigeration units often run on PLC‑style controllers that expose web interfaces for remote temperature monitoring. Those interfaces are attractive to attackers because they are usually left unpatched and, in many cases, use default credentials. Once inside, a hacker can: Force the unit into a continuous heating mode, creating fire hazards. Disrupt the cold‑chain, leading to spoilage and inventory loss. Use the device as a foothold to move laterally across the network. US agencies have warned that these attac