The denial-of-service attacks last week slowed down the websites of several Swedish authorities for several hours.

In a chat group with tens of thousands of members on Telegram, a pro-Russian group claimed responsibility.

The group criticized the expulsion of Russian diplomats and the ongoing investigation into sabotage against Nord Stream.

Pointing to Russia

Swedish police have now initiated several preliminary investigations and the suspicions are directed at actors in Russia:

"We have initiated a number of preliminary investigations that are ongoing. I can't say much about the ongoing preliminary investigation, but based on what you also see in this Telegram chat, there are many indications that it points that way, says Björn Eriksson, group manager at the department for complex cybercrimes at the police's national operations department.

The cases are primarily investigated by the Stockholm police region, but several other authorities are involved, according to Björn Eriksson.

– There is definitely someone with capacity behind this because they have succeeded in getting a downtime on these sites. But then DDoS is an easy thing to buy for a fairly cheap money, so you can get a pretty strong force in a denial of service attack just by paying a certain amount. There is nothing to say that it has to be a state actor in this case.

"The number of unreported cases is extreme"

The police are now appealing to more authorities to report if they have been affected.

"There are a few who report and the number of unreported cases is extreme. We need to obtain information in order to be able to investigate and possibly prosecute in the end. If we do not receive information, it is almost risk-free to commit these crimes against Sweden.

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The cyber security expert: Very costly attacks. Photo: Sebastian Strandberg/SVT