The UK government says the Russian military was directly responsible for 2017's NotPetya attack.
"The decision to publicly attribute this incident underlines the fact that the United Kingdom and its allies will not tolerate malicious cyberactivity", a statement said.
Foreign Office minister Tariq Ahmad said in a statement on Thursday that the Russian military was responsible for the attack, which initially targeted computers in Ukraine but quickly spread beyond its borders.
Ukraine's Secret Service (SBY) has not been shy about blaming Russian Federation for the NotPetya ransomware incident, going public with their accusations just days after the incident.
According to estimates, companies lost more than $1.2bn due to this attack.
"The attack masqueraded as a criminal enterprise but its goal was principally to disrupt", said the British government.
Mr Williamson said: "We have entered a new era of warfare, witnessing a destructive and deadly mix of conventional military might and malicious cyber attacks". It spread to companies that do business with Ukraine, including USA pharmaceutical company Merck, Danish shipping firm A.P. Moller-Maersk and FedEx subsidiary TNT.
Britain blamed Russian Federation on Thursday for a cyber-attack a year ago, publicly pointing the finger at Moscow for spreading a virus which disrupted companies across Europe including UK-based Reckitt Benckiser (RB.L).
"The attack masqueraded as a criminal enterprise, but its goal was principally to disrupt", the British Foreign Office said.
According to Russian anti-virus experts, almost 2,000 attacks were launched previous year, principally targeting the Ukrainian government networks and financial and energy assets in the country.
"Primary targets were Ukrainian financial, energy and government sectors", Foreign Office Minister Lord Ahmad said in the statement. "Its indiscriminate design caused it to spread further, affecting other European and Russian businesses".
Ahmad said the "reckless" attack cost organizations hundreds of millions of dollars.
In November, Theresa May accused Vladimir Putin of attempting to "sow discord" in the west by spreading misinformation.
Lord Ahmad directly called on Russian Federation in his statement "to be the responsible member of the worldwide community it claims to be rather than trying to secretly undermine it".