SolarWinds (2020)

The 2020 SolarWinds attack compromised 18,000 organizations, including the US Treasury and Microsoft, through malicious code inserted into Orion software updates by Russian intelligence agency SVR. The supply-chain attack — active for nine months — was called by Microsoft President Brad Smith "the most sophisticated cyberattack ever conducted." Compared to #5's Facebook breach, the SolarWinds incident affected 33 times more organizations and required a $2.8 billion revenue impact to SolarWinds alone. It set a new standard for sophistication in state-sponsored cyberattacks.