The Justice Department said Wednesday that about 3% of its email accounts could be compromised as part of a massive breach of federal government agencies that U.S. officials have linked to Russia.

What You Need To Know

  • The Justice Department disclosed on Wednesday that it was among the federal agencies harmed by a massive breach of government networks that U.S. officials have linked to Russia

  • About 3% of its email accounts could be compromised; no classified systems are believed to have been affected

  • It was not immediately clear whether the intrusion at the Justice Department and other agencies included access to data other than email 

No classified systems are believed to have been affected, according to a statement from Justice Department spokesman Marc Raimondi. It did not identify to whom who the potentially compromised email accounts may belong.

It was not immediately clear whether the intrusion at the Justice Department and other agencies included access to data other than email because Microsoft’s Office 365 includes multiple document-sharing and collaborative components.

The Justice Department's statement comes just a day after the U.S. government on Tuesday said the devastating hack of federal agencies is “likely Russian in origin,” adding the operation appeared to be an “intelligence gathering” effort.

The assessment was disclosed in a rare public statement from the FBI, ODNI, NSA, and CISA, member agencies of the Cyber Unified Coordination Group (UCG) created by the Trump administration following the hack.

President Donald Trump had previously raised without evidence the idea that China could be to blame.

The hacking campaign was extraordinary in scale, with the intruders having stalked through government agencies, defense contractors and telecommunications companies for months by the time the breach was discovered. Experts say that gave the foreign agents ample time to collect data that could be highly damaging to U.S. national security, though the scope of the breaches and exactly what information was sought is unknown.

An estimated 18,000 organizations were affected by malicious code that piggybacked on popular network-management software from an Austin, Texas, company called SolarWinds. Of those customers, though, “a much smaller number has been compromised by follow-on activity on their systems,” the statement said, noting that fewer than 10 federal government agencies have so far been identified as falling into that category.

This is a developing story. Please check back for updates. 

The Associated Press contributed to this article.