Officials from the U.S. and U.K. claim the Russian military was directly responsible for the NotPetya cyberattacks last June that caused billions of dollars in global damage, according to BBC.
Moscow, however, denies these allegations and calls them "Russophobic."
Here are seven things to know.
1. In June, NotPetya, a malware variant that spread through an update to Ukrainian tax accounting software, compromised government systems in Ukraine as well as operations at companies in the U.S. and Europe. Experts believe about 2,000 NotPetya attacks were launched.
2. The NotPetya malware, which was originally thought to be a variant of ransomware, permanently wiped victims' data from infected devices.
3. In August, Ukrainian police arrested a 51-year-old Nikopol resident they believed played a role in the attacks.
4. On Thursday, U.K. officials publicly accused Russia of being behind the attacks. Foreign Office minister Lord Ahmad of Wimbledon told BBC: "The UK government judges that the Russian government, specifically the Russian military, was responsible for the destructive NotPetya cyber attack."
5. "The UK and its allies will not tolerate malicious cyber activity," the foreign office said in a statement.
6. The White House agreed: "In June 2017, the Russian military launched the most destructive and costly cyber attack in history," a statement read, according to BBC. "This was also a reckless and indiscriminate cyber attack that will be met with international consequences."
7. Russia responded, calling the claims "groundless" and citing Russian businesses were among some of the victims. "It's not more than a continuation of the Russophobic campaign," Kremlin spokesman Dmitry Peskov said, according to BBC.