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Federal prosecutors on Thursday unsealed an indictment charging six Russian nationals with conspiracy to hack into the computer networks of the Ukrainian government and its allies and steal or destroy sensitive data on behalf of the Kremlin.

The indictment, filed in US District Court for the District of Maryland, said that five of the men were officers in Unit 29155 of the Russian Main Intelligence Directorate (GRU), a military intelligence agency of the General Staff of the Armed Forces. Along with a sixth defendant, prosecutors alleged, they engaged in a conspiracy to hack, exfiltrate data, leak information, and destroy computer systems associated with the Ukrainian government in advance of the Russian invasion of Ukraine in February 2022.

Targeting critical infrastructure with WhisperGate

The indictment, which supersedes one filed earlier, comes 32 months after Microsoft documented its discovery of a destructive piece of malware, dubbed WhisperGate, had infected dozens of Ukrainian government, nonprofit, and IT organizations. WhisperGate masqueraded as ransomware, but in actuality was malware that permanently destroyed computers and the data stored on them by wiping the master boot record—a part of the hard drive needed to start the operating system during bootup.