ISTANBUL 

Investigators have discovered evidence linking Russia to a cyberattack on the US federal court system that stores confidential legal documents, The New York Times reported Tuesday, quoting individuals familiar with the breach.

Hackers conducted a multi-year campaign to penetrate the system, though the specific Russian entity behind the intrusion and potential involvement of additional nations remain undetermined, according to the newspaper's sources.

Federal court officials recently warned Justice Department personnel and judges about hackers compromising protected case files, the newspaper claimed, citing an internal memorandum it obtained.

It reported that attackers appeared to initially focus on criminal case files involving international connections in no fewer than eight federal district courts.

American authorities have yet to disclose who conducted the cyberattack or detail the extent of compromised information.

US officials have not publicly made an announcement on the incident and Russia has not publicly commented.

The US Courts, however, confirmed late Thursday that it suffered cyberattacks on electronic case management systems containing confidential documents.

It said it is "taking additional steps to strengthen protections for sensitive case documents."​​​​​​​