FBI probing intrusion into a system managing sensitive surveillance information

The FBI is probing suspicious activity detected on an internal, unclassified system that contains law‑enforcement‑sensitive surveillance returns (including pen register and trap‑and‑trace data) and PII tied to investigations; the bureau reported attackers used "sophisticated" techniques and leveraged a commercial ISP's infrastructure, but has not attributed the activity or released technical indicators while assessing scope and impact.