The Justice Department has become the latest known victim of Russian hackers, who are engaged in an ongoing campaign of cyberespionage that has afflicted federal agencies and the private sector.

A department spokesman on Wednesday said that the department’s Office of the Chief Information Officer, which handles network security, learned on Dec. 24 of malicious activity linked to the hacking campaign.

The intrusions into other federal agencies and technology firms were discovered earlier last month, and in the Justice Department’s case involved its unclassified Office 365 email system, spokesman Marc Raimondi said.

Office 365 email is hosted on Microsoft’s Azure cloud — or servers operated by the tech giant.

“After learning of the malicious activity, the OCIO eliminated the identified method by which the actor was accessing the O365 email environment,” Raimondi said in a statement.

“At this point, the number of potentially accessed O365 mailboxes appears limited to around 3-percent and we have no indication that any classified systems were impacted,’’ he said.

The Justice Department joins the Departments of the Treasury, Commerce, State, Homeland Security and Energy with known breaches carried out by the Russian foreign intelligence service, the SVR.

The U.S. intelligence community declared Tuesday that the intrusions were “likely Russian in origin” — the agencies’ first formal acknowledgment that they believed Moscow behind the campaign.

The intelligence agencies also said that so far investigators have identified fewer than 10 federal entities that have had their networks breached, though as the investigation continues, more federal agencies may turn out to have been compromised.