Information Systems Security Partners (ISSP), a cyber-security firm, has linked the event to a 2015 breach and outage that affected 225,000 people. It also claimed that several other recent incidents in Ukraine were linked.

The current assault has yet to be formally traced to a state actor. However, Ukraine has stated that Russia launched hundreds of cyber operations against it in 2016.

Ukraine’s president, Petro Poroshenko, stated in December that hackers had targeted official institutions 6,500 times in the final two months of 2016.

He said that the occurrences demonstrated that Russia was waging a cyberwar against the country.

The Ukrainian government has accused Russia of being behind a cyber-attack on dozens of government websites on Friday.

In the greatest such attack on Ukraine in four years, around 70 government websites were momentarily taken offline.

Before the web pages were taken down, a message emerged urging Ukrainians to “be prepared for the worst.” Most of the sites’ access was restored within hours.

The United States and NATO denounced the attack and promised Ukraine their assistance. Russia has not responded to the breach.

Ukraine claims to have “proof” that Russia was behind a large cyber-attack that took offline vital government websites last week. At the same time, Microsoft warns that the intrusion might be significantly worse than previously thought.

Kyiv claimed late Friday that early evidence suggested Russian security agencies were behind the cyber-attack.