FBI announcement follows alleged targeting of mobile phones used by Donald Trump and JD Vance.
US authorities say they have uncovered “a broad and significant” cyberespionage campaign carried out by China-linked hackers aiming to steal information from Americans working in government and politics.
The FBI and the Cybersecurity and Infrastructure Security Agency (CISA) said in a joint statement on Wednesday that actors affiliated with Beijing had “compromised networks at multiple telecommunications companies”.
The hack enabled the “theft of customer call records data” and compromised the “private communications of a limited number of individuals”, the agencies said.
The FBI and CISA did not specify which individuals had been targeted but said they were “primarily involved in government or political activity”.
The hackers also accessed “information that was subject to US law enforcement requests pursuant to court orders”, the agencies said, suggesting they sought to compromise programmes subject to the Foreign Intelligence Surveillance Act (FISA), which grants spy agencies broad powers to surveil the communications of individuals suspected of being foreign agents.
The FBI and CISA said they expected their “understanding of these compromises to grow as the investigation continues”.
The announcement follows a series of high-profile hacking incidents that Washington has described as part of a broader strategy by Beijing to steal technological and government data, as well as target critical infrastructure in the US.
In September, the FBI said it had uncovered a far-reaching Chinese hacking campaign named Flax Typhoon.
The campaign involved the installation of malicious software on more than 200,000 consumer devices – including cameras, video recorders, and routers used in homes and offices – which were then used to form a network of infected computers capable of facilitating cybercrime, according to US authorities.
Last month, the FBI said it had launched an investigation into alleged Chinese hacking of mobile phones used by then-Republican presidential nominee Donald Trump and his running mate JD Vance.
The hackers, who also allegedly targeted people associated with Democratic nominee Kamala Harris, had reportedly infiltrated the network of US mobile phone provider Verizon.
The FBI and CISA did not specify if or how the most recent hacking efforts were connected to these earlier campaigns.