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.

"The U.S. government's continued investigation into the People's Republic of China (PRC) targeting of commercial telecommunications infrastructure has revealed a broad and significant cyber espionage campaign," the agencies said Wednesday in a joint release.

The FBI and CISA have confirmed that Salt Typhoon, a hacking group linked to the Chinese government, has compromised US government networks.

CISA and the FBI have confirmed that Chinese hackers compromised the networks of telecommunications companies to spy on specific targets.

Federal authorities say an investigation into Chinese government hacking efforts has revealed a “broad and significant” cyberespionage campaign mounted by Beijing

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

A federal investigation into Chinese government efforts to hack into U.S. telecommunications networks has revealed a “broad and significant” cyberespionage campaign aimed at stealing information from Americans who work in government and politics,

An FBI investigation into reported hacks at AT&T and Verizon reveals 'a broad and significant cyber espionage campaign,' the agency says.

The U.S. government’s ongoing probe into China-backed actors’ attempts to hack into U.S. telecommunications infrastructure revealed a “broad and significant” espionage campaign targeted at those in government or political work,