The U.S. Justice Department is investigating a cyber breach involving the federal court records management system, the department's top national security attorney told lawmakers on Thursday.

Matt Olsen, head of the Justice Department's National Security Division, alluded to the threat of cyber attacks by foreign nations as he informed the U.S. House Judiciary Committee about the investigation into an "effort to compromise public judicial dockets."

Olsen made those remarks in response to questions from Representative Jerrold Nadler of New York, the panel's Democratic chairman, who said the committee had only in March learned of the "startling breadth and scope" of the breach.

The Administrative Office of the U.S. Courts in January 2021 said it was adding new security procedures to protect confidential or sealed records following an apparent compromise of its electronic case management and filing system.

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Department of Justice building

The entrance signage for the United States Department of Justice Building in Washington D.C., USA. The Department of Justice has charged a man accused of purchasing dozens of firearms in a six-month span in which some were used in crimes.  (iStock)

The federal judiciary at the time said that vulnerabilities had been identified as a result of the breach that risked compromising highly sensitive non-public documents stored with the courts.

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Olsen said he could not speak "directly to the nature of the ongoing investigation." But he noted his division was focused on the risk of cyber attacks by foreign nations like China, Russia, Iran and North Korea.

Cyber Attack illustration

FILE PHOTO: Figurines with computers and smartphones are seen in front of the words "Cyber Attack", binary codes and the Russian flag, in this illustration taken February 15, 2022. REUTERS/Dado Ruvic/Illustration/File Photo (REUTERS/Dado Ruvic/Illustration/File Photo)

"This is of course a significant concern for us given the nature of the information that is often held by the courts," Olsen told lawmakers, adding the department was working with the judiciary to investigate and address the matter.

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The Administrative Office, the judiciary's administrative arm, had no immediate comment.

Attorney General Merrick Garland at podium

U.S. Attorney General Merrick Garland speaks at the Department of Justice,  in advance of the one year anniversary of the attack on the U.S. Capitol, in Washington, Wednesday, Jan. 5, 2022.  (Carolyn Kaster/Pool via REUTERS)

The judiciary has been working to modernize its electronic case management and filing system and the related online portal known as PACER, which is used to access records, citing the risk of cyber attacks on the aging electronic system.

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"We are vulnerable," U.S. Circuit Judge Amy St. Eve testified at a House committee hearing in May on the judiciary's budget request.