The FBI deemed a recent China-linked cyber intrusion into a sensitive agency surveillance system a “major incident,” meaning it poses significant risks to U.S. national security, according to one congressional aide and two U.S. officials with knowledge of the matter.
https://www.politico.com/news/2026/04/01/fbi-hack-surveillance-system-major-incident-00854237
FBI declares suspected Chinese hack of US surveillance system a ‘major cyber incident’

The designation suggests the hackers successfully compromised swathes of sensitive data stored directly on FBI systems.

Politico