Cyber hackers defrost supermarket freezers across Europe weeks after similar attack that ...

The UK is on alert after cyber-hackers targeted supermarket fridges and freezers across Europe, turning up the temperature of the units overnight.

Ireland, Sweden , Belgium and Estonia were among the countries affected.

The UK's National Cyber Security Centre has now issued advice to retailers to patch vulnerabilities in their systems.

It comes a month after hackers ramped up the temperature of cooling units at hundreds of French supermarkets, causing food losses and fires.

The French hacks affected fridges supplied by Danfoss, which also works with British supermarkets including Tesco and Sainsbury's .

Supermarket chains Ahold Delhaize and Colruyt said an IT incident overnight hit fridges and freezers in dozens of stores in Belgium and Luxembourg.

Carrefour Belgium reported on Monday morning that fifteen of its stores have been affected so far.

Ikea said its retail refrigeration control systems at one store in Belgium had also been affected and said it 'cannot rule out' whether additional locations have been affected.

Swedish grocers ICA and Coop reported similar temperature spikes.

An employee cleans refrigerators at the ICA Baronen store on Odengatan street in Stockholm, Sweden, after freezer temperatures at several Swedish grocery stores rose sharply overnight

Stephan Moelans, CEO of Belgian refrigeration firm Sabcobel, which operates Delhaize's systems, told the Belga news agency the incident was a cyberattack, with units' evaporators switched to defrost mode. Moelans's office declined to .

'We've been working all night and morning to disconnect the affected units from the network,' Mr Moelans told Belga.

Engla Ingwall, sales manager at an ICA store in Stockholm, told Reuters: 'There has been a cyberattack and all our freezers reached 50 degrees (Celsius)... Everything is destroyed.' She added that the attack occurred at 2am local time but was only noticed hours later.

A spokesman at ICA said that the company was aware that a 'limited number of stores were affected by an incident overnight, which impacted their refrigeration and freezer systems'.

Grocery retail group Coop told Swedish newspaper Aftonbladet that six of its stores had been affected by similar incidents.

Sweden's national cyber-security centre said it was working on several incidents affecting refrigeration systems in grocery stores across the country.

In Ireland, food wholesaler Musgrave said that a suspected cyber incident had targeted fridges and freezers in 13 of its SuperValu stores, meaning some chilled and frozen products had to be thrown away.

'Our monitoring systems alerted us to the issue, and we took immediate action,' it said in a statement. 'Our investigation is ongoing.'

In Estonia, refrigerator company Kitman Coldtech said a cyberattack targeted refrigeration systems at an unnamed supermarket chain, but a quick response meant there was no damage.

The latest incidents follow an attack in France last month, in which police said hackers seized control of cooling units at hundreds of supermarkets, causing fires and food losses.

French supermarket staff were seen throwing cartfuls of defrosted frozen foods into a giant trash container, with molten ice cream sloshing out of broken tubs on the street.

While no one has claimed responsibility for either attack, the cases have put a spotlight on rising anxiety over hybrid attacks spreading from conflicts on European borders after Russia's 2022 invasion of Ukraine.

Moscow has repeatedly denied involvement in any sabotage or hybrid warfare operations.

It is unclear who was behind Monday's attacks, or if they were linked to last month's incidents.

Sweden's national cybersecurity centre said it could not speculate on who was behind the attacks. The head of the centre, John Billow, said it is working on several incidents affecting grocery stores across the country.

'We have in recent weeks... identified that we have quite a lot of exposed operational technology devices in Sweden that we have been clear the necessity to update or patch,' he said.

Employees throw away bags of spoiled refrigerated food outside an ICA supermarket on Odengatan street in Stockholm

Supermarket cold aisles are typically run by control panels that manage an entire store's fridges and freezers and can be accessed over the internet, which lets maintenance companies adjust them from anywhere.

From refrigerators and heating systems to security cameras and alarm networks, an expanding range of devices – once largely mechanical – can now be monitored and controlled remotely, creating new opportunities for cyber-criminals.

A spokesman for Colruyt Group, which operates Spar stores in Belgium, said five shops had their fridge systems attacked.

Tom Hegel, a researcher at cybersecurity firm SentinelOne, said that attacks were usually extortion, politically motivated or nation-state-level operations, with the lack of financial demands in the recent supermarket cases pointing to sabotage.

'Retail is an easy target because retail chains run enormous estates of refrigeration controllers, building management systems, door access panels and point-of-sale gear,' he said.

'Grocery margins are thin, and stock perishes within hours, so any disruption hurts quickly and in public.'