The department said 80% of Microsoft email accounts used by employees in the four U.S. attorney offices in New York were breached. All told, the Justice Department said 27 U.S. Attorney offices had at least one employee’s email account compromised during the hacking campaign.

The Justice Department said in a statement that it believes the accounts were compromised from May 7 to Dec. 27, 2020. Such a timeframe is notable because the SolarWinds campaign, which infiltrated dozens of private-sector companies and think tanks as well as at least nine U.S. government agencies, was first discovered and publicized in mid-December.

The Biden administration in April announced sanctions, including the expulsion of Russian diplomats, in response to the SolarWinds hack and Russian interference in the 2020 U.S. presidential election. Russia has denied wrongdoing.