European supermarkets once again become targets of cyberattacks, with hackers remotely heating refrigerators, causing food to spoil.

This attack caused a significant rise in the temperature of refrigerators and freezers; at least one store reported temperatures as high as 50 degrees Celsius (122 degrees Fahrenheit), while other retailers were forced to discard food. This has also raised concerns within the retail industry.

Which countries and retailers are affected?

It is reported that dozens of Delhaize stores of the Dutch supermarket group Ahold Delhaize in Belgium and Luxembourg have been affected.

This Dutch supermarket giant informed CNBC that on Monday, incidents occurred with the cooling systems in dozens of its stores, resulting in the need to discard food. The company stated that the situation has now returned to normal, and all stores have resumed full operations.

Meanwhile, Colruyt Group reported that its 5 Spar stores in Belgium were attacked, according to Reuters. The French supermarket chain Carrefour informed BBC that its 15 stores in Belgium also suffered attacks. The French company Intermarch also stated that 15 out of its 153 stores in Belgium were affected.

Intermarch A spokesperson told CNBC: "In most cases, the existing security measures enable us to quickly take control of the attacks."

"However, a few stores did experience inventory losses, although they are not the same as those during the attack in mid-October."

"Based on the information we currently have, most of the impact of the attack has fallen on other participants in the industry, especially Carrefour and Delhaize," the spokesperson added.

IKEA informed CNBC that their store located in Mons, Belgium (Mons), experienced a network issue from Sunday to Monday, which affected the refrigerators and freezers.

Although the store is still open to customers, the company is checking the affected equipment and products, as well as verifying their installation in other stores in Belgium.

IKEA A spokesperson stated via email, "This incident has a limited impact on our restaurant and the supply in the Swedish food market."

"We are continuing our investigation to determine what exactly happened."

Sweden's largest food and grocery retailer, ICA, also confirmed that the company has become aware of incidents at “a few stores” that use networks not within the central system of ICA. “This incident affected the stores’ refrigeration and freezing systems. ICA is currently assisting the affected stores in dealing with this matter,” the company stated in an email.

In addition, Finnish supermarket Kesko, Irish chain grocer Supervalu, and Estonian grocer One Selver also reported that their refrigeration systems were disrupted.

Carrefour did not immediately respond to CNBC's request for a comment.

What is the connection between the events on Monday and the cyberattacks in October?

In October, hundreds of French supermarkets were subjected to cyberattacks, resulting in fires, overheated refrigerators, and spoiled food.

Intermarch's parent company, Les Mousquetaires, informed CNBC at that time that the expected losses would amount to several million euros.

"Food safety needs to receive more attention at all levels, as the weaponization of food has become a reality," said the EU Commissioner for Agriculture and Food Affairs Christophe Hansen in October on X.

At the end of August, there were also malfunctions with freezing equipment in the canteens of six U.S. military bases.

Reuters cited four sources with knowledge of the matter in October, stating that the Pentagon is currently treating these incidents as suspected cyberattacks and is coordinating with French authorities.

In one instance, the refrigerator temperature was raised at night, resulting in a large amount of food melting and spoiling by morning.

Sophos Counter Threats Unit Senior Threat Intelligence Director Rafe Pilling told CNBC that although there is no evidence to suggest that artificial intelligence played a role in these attacks, in other cases, criminals have been using AI to accelerate the scale and efficiency of their attacks.

Why does this happen?

So far, no organization or malicious actor has claimed responsibility for this, and the investigation is still ongoing. However, this has raised concerns about the vulnerability of critical infrastructure.

Visente AB Strategic Cybersecurity Advisor Fredrik Blix stated that this hacker attack was not particularly complex, as the control units of these refrigerators were "directly connected to the public internet," and they came with built-in support for login information. The passwords could be obtained on the same day based on information released by researchers in August.

"The supplier fixed this issue in August," Blix said in a post on LinkedIn, "Tens of thousands of devices never received the update, and the oldest models are simply not updatable at all."

He added that France also suffered the same attack three weeks ago, and the French authorities have requested that European operators disconnect these devices from the internet. “I want to ask the suppliers and service companies that install and remotely manage such devices: what exactly have you done during these three weeks?”

Blix pointed out that the silence behind the attacks is the most “interesting clue” because it rules out ransomware gangs, leaving only two possibilities: either someone is doing it simply because they have the capability, or someone wants to create “unrest” in countries that support Ukraine without leaving any traces.