Based on interviews it had conducted, Reuters stated that hackers had been active testing the defenses of the Baltic grids for the past two years. Similar attacks carried out against Ukraine’s energy infrastructure did considerable damage to the local network.

Reuters’ sources claim that Russian state organizations are behind the attacks, though the agency wasn’t able to verify this information independently.

An attack against an Internet gateway of one of the grids disrupted operations, but didn’t knock out the network in question. Another attempt involved a petrol distribution system.

Though the attacks referred to by Reuters’ sources happened more than a year ago, some of them were still being investigated, the agency reported, as attackers sometimes became active months after actually infiltrating a system, as had been the case in the 2015 attack on the Ukrainian electricity grid.

According to Reuters, NATO and cyber security experts see the attempts at disrupting Baltic systems as a way of testing the defenses of the local grids, with a potential view to completely disrupting them in case of conflict.

The grid operators of Estonia, Latvia, and Lithuania all closely observed the situation, Reuters reported. According to security officials, the incidence of attacks typically increases whenever the Russian military conducts exercises close to the border.

The Baltic states as well as NATO have been aware of the issue on a broader scale for a while. Within the alliance, the NATO Centre of Excellence for Energy Security (ENSEC COE) in Vilnius is addressing the issue, similar to the cyber defense centre in Tallinn.