A cyber attack that has affected supermarkets across Europe also hit cold storage sites used by France’s national blood service, it has emerged.
Hackers accessed control units for fridges containing blood samples and programmed them to raise to temperatures of 110°C, local media reported.
Supermarkets that fell victim in the second wave of cyber attacks were rushing to upgrade their systems and protect themselves against further hacking attempts.
Shops in eight European countries were forced to throw away vast quantities of food after hackers tampered on Monday with their fridges, in an attack identical to one that swept dozens of supermarkets in France three weeks ago.
Coolworld, a company that stores containers for the French Blood Establishment (EFS) as part of a health monitoring system related to blood transfusions was among the companies affected, Le Canard reported.
The temperature increase from the usual -30°C was spotted in time, the organisation said. France’s Health Ministry said the incident caused no operational consequences due to the early detection.
In Sweden, supermarket chain Coop said it was switching systems to 5G networks and modern modems, instead of 4G connections - a process that had already started since the French incident.
The seven shops hit by the attack are back up and running but their refrigeration systems have been disconnected from the internet, a representative said.
"We are looking quite thoroughly and deeply into the status of the entire network of stores to see if we risk any vulnerability anywhere in the entire network," the representative added.
Software provider Danfoss, whose systems were again among those struck, said it has been in close contact with customers over the past three weeks to help them manage the situation, and recommended that systems should not be directly accessible through the internet.
“Retailers need to act now. They should identify whether their refrigerator controllers are vulnerable, check if they are connected to the internet, ensure they've got the latest security updates and are supported by the manufacturer. And if they don’t even know, then remove them from the public internet immediately,” said Frank Groenewegen, cybersecurity expert at Deloitte in The Hague.
“With disconnecting, you haven’t fixed the root cause but you’ve at least isolated those systems so that an attacker is not able to do this anymore.”
German supermarket operator Edeka, which had fridges hacked at a store in Reisbach, Germany, said there are no standardised refrigeration systems across its network of stores run by independent retailers.
EU cybersecurity agency ENISA said the large-scale nature of the cyber attacks aimed at the retail sector across several member states "underscores the importance of European co-operation, rapid information-sharing and co-ordinated responses to cyber incidents".
In Britain, hackers tried to target small meat-processing firms but the impact was minimal, said Richard Horne, chief executive of the National Cyber Security Centre (NCSC).
The NCSC is working with organisations to spot vulnerabilities and close them before somebody exploits them.
The attack on supermarket fridges is just an early sign of what are likely to be increasingly frequent disruptions as old technology fails to keep pace with hackers, Mr Horne said.
