Chinese state-linked hackers breached mobile phones at "the heart of Downing Street" amid a global cyber-espionage campaign over several years targeting telecommunication networks, according to reports.

U.S. officials first alerted its allies in 2024 after finding out that hacking groups had gained access to telecom companies around the world, according to The Associated Press.

The campaign reportedly targeted multiple countries, including the U.S. and the other members of the Five Eyes intelligence alliance: Australia, Canada and New Zealand.

The breaches allegedly gave China access to the phone data of millions and the possible ability to eavesdrop on calls, read text messages and track users’ locations.

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The hackers also had the ability to record calls "at will" according to Anne Neuberger, who was a deputy U.S. national security adviser between January 2021 and January 2025, The Telegraph reported.

Neuberger said that the "Chinese gained access to networks and essentially had broad and full access," giving them the capability to "geolocate millions of individuals, to record phone calls at will."

U.S. intelligence agencies believe the breaches date back to at least 2021, but they were only identified and disclosed by U.S. authorities in 2024.

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In 2024, The Associated Press reported that U.S. federal authorities urged telecommunication companies to boost network security. The guidance, issued by the FBI and the Cybersecurity and Infrastructure Security Agency, was to help root out the hackers and prevent similar attacks in the future.

A joint cybersecurity advisory was issued in August 2025, with the U.S. National Security Agency (NSA) and allied partners warning that Chinese state-sponsored actors were targeting networks globally.

"The malicious activity outlined in the advisory partially overlaps with cybersecurity industry reporting on Chinese state-sponsored threat actors referred to by names such as Salt Typhoon," an NSA release said.

In the U.K., officials raised concerns that senior government figures may also have been exposed. One source told The Telegraph that the breach went "right into the heart of Downing Street."

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Similarly, The Telegraph was told that there were "many" different hacking attacks on the phones of Downing Street staff and across wider government, especially when Rishi Sunak was prime minister between 2022 and 2024.

Yuval Wollman, a former Israeli intelligence chief, also told The Telegraph that Salt Typhoon was "one of the most prominent names" in the cyber-espionage world.

"While much of the public reporting has focused on U.S. targets, Salt Typhoon’s operations have extended into Europe, the Middle East and Africa, where it has targeted telecoms firms, government entities and technology companies," Wollman of cybersecurity platform CyberProof added.

In the past, China’s foreign ministry dismissed the claims as "baseless" and "lacking evidence," according to The Telegraph.

Fox News Digital has reached out to Downing Street for comment.