FBI probing intrusion into a system managing sensitive surveillance information

The Federal Bureau of Investigation (FBI) is probing suspicious activity on an internal system containing sensitive surveillance and investigation data.

The FBI is investigating suspicious cyber activity affecting an internal system that stores sensitive data tied to surveillance operations and investigations, The Associated Press reports. According to a notification sent to members of the United States Congress, the bureau is assessing the scope and potential impact of the incident.

The investigation into abnormal log activity related to an internal network system began on February 17, 2026. Although the system is unclassified, it stores law-enforcement sensitive data, including surveillance records from legal tools such as pen register and trap-and-trace orders, along with personally identifiable information linked to investigations.

A pen register is a surveillance tool used by law enforcement agencies to record numbers dialed from a phone line. It collects call metadata but not content, helping investigators map communication patterns and identify contacts during investigations.

“The affected system is unclassified and contains law enforcement sensitive information, including returns from legal process, such as pen register and trap and trace surveillance returns, and personally identifiable information pertaining to subjects of FBI investigations,” reads the notification, according to The Associated Press.

The FBI confirmed the incident, stating it had identified and addressed suspicious activity on its networks using all available technical capabilities.

“The FBI identified and addressed suspicious activities on FBI networks, and we have leveraged all technical capabilities to respond,” the FBI said. “We have nothing additional to respond.”

The bureau did not reveal further details nor attribute the attack to any threat actors. The FBI noted the attackers used “sophisticated” techniques, including exploiting a commercial ISP’s infrastructure, reflecting long-standing foreign targeting of U.S. federal agencies for espionage.

In early August, Politico reported a major cyberattack on the federal judiciary’s electronic case filing system, potentially exposing sensitive court data across multiple states. The breach may have compromised the identities of confidential informants in federal criminal cases. The Administrative Office of U.S. Courts first assessed the severity around July 4, involving the Justice Department and affected district courts.

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Pierluigi Paganini

(SecurityAffairs – hacking, newsletter)