Supermarket managers across Europe are being warned to upgrade their software systems after hackers caused millions of euros of damage by ordering freezers to defrost.
The cyberattack on Monday impacted dozens of supermarkets in seven European countries, and was similar to one that hit up to 700 supermarkets in France last month.
The latest incident — which affected supermarkets in Belgium, Estonia, Finland, Luxembourg, the Netherlands, Ireland, Sweden, and the UK — happened in spite of companies working hard since the French attack to upgrade their systems.
Stephan Moelans, CEO of Sabcobel, which makes software that controls supermarket freezers, told the Belga News Agency his company worked "all night and morning to disconnect the affected units from the network".
He said Sabcobel looks after the computer systems used by the Belgian supermarket chain Delhaize, which had freezers in 40 of its outlets in Belgium and Luxembourg hit by hackers.
Moelans said in addition to software updates, supermarkets will need to carry out physical modifications if they are to be safe from future attacks.
"The simplest solution is to manage the fridges over a secure internet connection," he said. "Most of our customers switched to that after the attack in France."
He said the vast majority of supermarkets in Europe are linked to the internet, so engineers can carry out maintenance and troubleshooting remotely. But those links have also offered hackers a route in.
Reuters quoted Engla Ingwall, a sales manager at an ICA franchise store in Stockholm, Sweden as saying the attack happened at around 2 am, but was not noticed at her store until several hours later.
Supermarket chains hit by the attack include Ahold Delhaize and Colruyt in Belgium and Luxembourg and the Swedish company Coop.
This week's attack and the one last month in France have been linked to a similar suspected cyberattack in the United States in August, in which freezers malfunctioned at several military bases.
Experts say the incidents highlight the growing threat posed by hackers using artificial intelligence to damage infrastructure and cause chaos.
Katrien Eggers, a spokeswoman for Belgium's Center for Cybersecurity, told Reuters: "It is not known who is behind this attack, and it may never be determined."
She said "all IT systems are potentially vulnerable" and AI "can now be used to successfully exploit these weaknesses".
Eggers said heating systems, security cameras, and alarms could all potentially be controlled remotely by hackers exploiting such weaknesses.
Christophe Hansen, the European Union's commissioner for agriculture, said the bloc is becoming increasingly concerned about such attacks.
