The British government is blaming Russia for the massive notPetya malware attack that infected machines all over the world last June.

A statement issued by the government Thursday states that the United Kingdom’s National Cyber Security Centre concluded that Moscow’s military was “almost certainly” responsible for the cyberattack, which first broke out in Ukraine and then spread to businesses and organizations elsewhere in Europe and the United States.

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U.K. officials said the government's decision to publicly attribute the attack to Russia aims to reiterate the position of the U.K. and its allies “that malicious cyber activity will not be tolerated.”

The U.S. has not publicly attributed the attack.

The computer virus, which experts concluded masqueraded as ransomware but was in fact designed to destroy data, spread rapidly to machines throughout the world last June. It locked individuals out of their computer systems and demanded $300 in bitcoin payments, though individuals who paid the ransom did not regain access to their files.

While the virus also affected some systems in Russia, there were suspicions early on that Moscow was behind the attack, because Ukraine appeared to be the intended target.

“The Kremlin has positioned Russia in direct opposition to the West: it doesn’t have to be that way. We call upon Russia to be the responsible member of the international community it claims to be rather than secretly trying to undermine it,” Foreign Office Minister Tariq Ahmad said.

Russia is denying that it was responsible for the cyberattack.

The attack impacted global shipping giant A.P. Moller-Maersk and forced the largest terminal at the Port of Los Angeles to shut down operations for several days.

Last year, FedEx reported losses of $300 million due to the cyberattack.

Ahmad said Thursday that the attack “disrupted organizations across Europe costing hundreds of millions of pounds.”

The malware, dubbed notPetya by many, leveraged a tool widely believed to have been stolen from the National Security Agency that exploits a vulnerability in Microsoft Windows. Microsoft had issued a patch for the flaw, but systems throughout the world remained unpatched, leaving them vulnerable.

The outbreak of notPetya occurred less than two months after the global WannaCry cyberattack. The two attacks so close together have underscored the global malware threat.

The United States and the U.K. have both blamed North Korea for WannaCry.

Ahmad emphasized Thursday that the British government is “identifying, pursuing and responding to malicious cyber activity regardless of where it originates, imposing costs on those who would seek to do us harm.”

“We are committed to strengthening coordinated international efforts to uphold a free, open, peaceful and secure cyberspace,” Ahmad added.

This post has been updated.