The FBI and CISA previously said they were investigating breaches by a China-backed hacking group inside several telecommunications providers but had not said whether any data was stolen or whether the hackers accessed the systems used to fulfill legal wiretap requests.

Hackers linked to Beijing have compromised the systems of multiple telecoms firms to access call records and private communications.

The U.S. government has confirmed that hackers with links to China breached multiple U.S. telecommunication service providers to access the wiretap systems used by law enforcement to surveil Americans.