SOLARWINDS

The cyber attack was called "SolarWinds", which compromised nine U.S. federal agencies and hundreds of private sector companies.

Russia's spy chief on May 18 denied responsibility for the SolarWinds cyber attack but said he was "flattered" by the accusations from the United States and Britain that Russian foreign intelligence was behind such a sophisticated hack.

Poland on Thursday said it had expelled three Russian diplomats, following a similar move by the United States, over what Warsaw called "hostile actions" by Moscow.

The US has announced sanctions against Russia in response to what it says are cyber-attacks and other hostile acts.

The measures, which target dozens of Russian entities and officials, aim to deter "Russia's harmful foreign activities", the White House said.

The Biden administration on April 15 announced the expulsion of 10 Russian diplomats and sanctions against nearly three dozen people and companies as it moved to hold the Kremlin accountable for interference in last year's presidential election and the hacking of federal agencies.

The Biden administration is preparing to announce sanctions in response to a massive Russian hacking campaign that breached vital federal agencies, as well as for election interference, a senior administration official said.

The US administration has completed an intelligence review of Russia's alleged election interference and the SolarWinds hack and may soon announce retaliatory actions, Bloomberg reported, citing "three people familiar with the matter."

U.S. intelligence and law enforcement agencies said on Jan. 5 that Russia was probably behind the massive SolarWinds hack that has shaken government and corporate security, contradicting President Donald Trump, who had suggested China could be to blame.

The hacking group behind the SolarWinds compromise was able to break into Microsoft Corp and access some of its source code, Microsoft said on Dec. 31, something experts said sent a worrying signal about the spies' ambition.

President Donald Trump on Dec. 19 downplayed a massive cyberattack on U.S. government agencies, declaring it "under control" and undercutting the assessment by his own administration that Russia was to blame.