China's Salt Typhoon cyberspies have stolen data from millions of Americans through a years-long intrusion into telecommunications networks, according to senior FBI officials. The campaign represents one of the most significant espionage breaches uncovered in the United States.

The Beijing-backed operation began in 2019 and remained hidden until last year. Authorities say at least 80 countries were affected, far beyond the nine American telcos initially identified, with around 200 US organisations compromised.

Targets included Verizon, AT&T, and over 100 current and former administration officials. Officials say the intrusions enabled Chinese operatives to geolocate mobile users, monitor internet traffic, and sometimes record phone calls.

Three Chinese firms, Sichuan Juxinhe, Beijing Huanyu Tianqiong, and Sichuan Zhixin Ruijie, have been tied to Salt Typhoon. US officials say they support China's security services and military.

The FBI warns that the scale of indiscriminate targeting falls outside traditional espionage norms. Officials stress the need for stronger cybersecurity measures as China, Russia, Iran, and North Korea continue to advance their cyber operations against critical infrastructure and private networks.