Last summer, a hacking group that primarily communicates in Russian managed to infiltrate the email addresses of approximately 632,000 employees working for the US Departments of Defense and Justice.

This information was disclosed in a report obtained through a Freedom of Information Act request, as reported by Bloomberg on Monday.

As per a report released by the US Office of Personnel Management (OPM) in July, the cyberattack exploited vulnerabilities in MOVEit, a commonly used file transfer tool. 

During the attack, an unauthorized actor purportedly obtained access to government email addresses, links to government employee surveys overseen by OPM, and internal OPM tracking codes.

This incident affected employees across multiple sectors, including the Department of Justice and various branches of the Pentagon, such as the Air Force, Army, US Army Corps of Engineers, the Office of the Secretary of Defense, the Joint Staff, and Defense Agencies and Field Activities, according to the report.

The OPM categorized the hack as a "major incident," but it held the belief that it did not present a significant risk due to the compromised data being "generally of low sensitivity," as stated in the report.

This comes against the backdrop of the ongoing conflict in Ukraine.

The eastward expansion of NATO prompted Russian President Vladimir Putin to address the matter promptly as it posed a direct threat to Russia's national security.

In February 2022, Russia announced the launch of its Special Military Operation and has since then annexed several territories, including the regions of Donetsk, Kherson, Luhansk and Zaporozhye

Read more: Networks of over 30 Israeli companies breached by 'Iranian hackers'

In July this year, the Russian RaHDit hacker group published the data of 1,700 employees of the Security Service of Ukraine, as well as that of 2,000 military personnel of the Ukrainian Navy.

According to the hacker group, the data on the Security Service employees was unveiled in response to the attack on the Crimean Bridge on July 17.

It is reported that the hackers also leaked data on members of the UA Cats Division, a volunteer organization that collects donations for sea drones for Ukraine, as it is speculated that the attack was carried out using these unmanned vehicles.

In further response to the attack, RaHDit unveiled the routes of civilian ships it is thought that the naval drones with explosives were launched from toward the bridge.