The US Department of Justice (DoJ) said that the attackers behind the SolarWinds supply chain attack have gained access to roughly 3% of the department’s Office 365 email inboxes. The Justice Department currently employs over 115,000 people, which translates to around 3450 potentially breached mailboxes. Only 10 US government agencies have been targeted by additional hacking activity after the initial breach. A joint FBI, CISA, NSA, and ODNI statement also said that a Russian-backed Advanced Persistent Threat (APT) group is likely behind the attacks.
Source: https://www.bleepingcomputer.com/news/security/solarwinds-hackers-had-access-to-over-3-000-us-doj-email-accounts/