The Norwegian Police Security Service (PST) says that pro-Russian hackers took control of critical operation systems at a dam and opened outflow valves.

The attack occurred in April and is thought to have been a demonstration of Russia’s ability to remotely hack critical infrastructure in the country.

At the Arendalsuka annual national forum in the city of Arendal, the head of the PST, Beate Gangås, spoke about the incident saying that it was less of an attempt to cause damage than a display of what the hackers can do.

“They don’t necessarily aim to cause destruction, but to show what they are capable of,” stated Gangås during her talk about the sabotage operation.

“The purpose of these kinds of actions is to exert influence and create fear or unrest in the population,” the PST chief also stated, noting that Russia has become more dangerous.

According to local media reports, the hackers compromised a digital system controlling the water flow at the Bremanger dam, and set the outflow valves to open position.

It took dam operators roughly four hours to discover and reverse the malicious valve setting. By that time, though, more than 7.2 million liters (1.9 million gallons) of water had flown through.

Norway’s National Criminal Investigation Service (Kripos) reached the same conclusion in June, based on videos that Russian hacktivists published on the Telegram messaging service to prove their intrusion.

Specifically, the hacktivists published a three-minute video showing the dam’s control panel, featuring a watermark associated with a pro-Russian cybercriminal group.

Such acts have been previously associated with state-sponsored groups like Sandworm (APT44), and aimed at exaggerating impact claims to create fear and uncertainty, and to publicly humiliate compromised organizations.

This is the second time Russia is associated with attacks against Norwegian entities, the previous one being a distributed denial-of-service (DDoS) attack on the country’s state services.

Norway’s Intelligence Chief, Nils Andreas Stensønes, stated that, while Norway is not at war with Russia, President Putin maintains tension through hybrid attacks against the entire West.

Stensønes characterized Russia as an unpredictable neighbor and the biggest threat that Norway faces currently.