Washington DC - The US Department of Justice said it broke up a Russian cyber espionage operation that stole sensitive data from computers in the US and other NATO members over several years.

Hackers used various versions of the Snake malware, traced by investigators to a unit of the Russian domestic intelligence service FSB called Turla.

Hundreds of computer systems in at least 50 countries were attacked for nearly 20 years, according to a US government statement issued late on Tuesday. US investigators attribute the sophisticated malware to a unit of Russia's Federal Security Service (FSB).

"For 20 years, the FSB has relied on the Snake malware to conduct cyberespionage against the United States and our allies – that ends today," said Assistant Attorney General Matthew G Olsen of the Justice Department’s National Security Division.

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"We will continue to strengthen our collective defenses against the Russian regime’s destabilizing efforts to undermine the security of the United States and our allies," said Attorney General Merrick B. Garland.

US investigators worked with other governments, the FBI, and the US Attorney's Office in an operation code-named Medusa.

The FBI developed a program to disable the malware that the FSB unit had repeatedly renewed and revised to ensure it remained the Kremlin's most sophisticated hacking software.

For victims of the attacks outside the US, the FBI is working with local authorities to inform them about the malware in their countries.