China Used 'Mass Surveillance' on Thousands of Americans' Phones, Report Claims

A mobile security expert has accused China of exploiting cellphone networks in the Caribbean to conduct "mass surveillance" on Americans.

Gary Miller, a former vice president of network security at California-based analytics company Mobileum, told The Guardian he had amassed evidence of espionage conducted via "decades-old vulnerabilities" in the global telecommunications system.

While not explicitly mentioned in the report, the claims appear to be centered around Signaling System 7 (SS7), a communications protocol that routes calls and data around the world and has long been known to have inherent security weaknesses.

According to Miller, his analysis of "signals data" from the Caribbean has shown China was using a state-controlled mobile operator to "target, track, and intercept phone communications of U.S. phone subscribers," The Guardian reported.

Miller claimed China appeared to exploit Caribbean operators to conduct surveillance on Americans as they were traveling, alleging that attacks on cell phones between 2018 to 2020 likely affected "tens of thousands" of U.S. mobile users in the region.

"Once you get into the tens of thousands, the attacks qualify as mass surveillance," the mobile researcher said, noting the tactic is "primarily for intelligence collection and not necessarily targeting high-profile targets." Miller continued: "It might be that there are locations of interest, and these occur primarily while people are abroad."

Exigent Media, a media production business founded by Miller, has been contacted for comment about the analysis supplied to The Guardian. A threat report titled Far From Home is currently listed as for sale on the company's website for $229.

A previous analysis paper covering 2018-2019, also titled Far From Home, contained a series of similar espionage claims about SS7, alleging that "mass surveillance attacks" in 2018 were most prevalent by China and Caribbean mobile networks.

The report noted that SS7 is a patchwork system that helps "network operators around the world to communicate with each other for international roaming services." But it warned the system leaves "fingerprints" that are used for tracking or monitoring.

Worries about SS7 vulnerabilities are far from new. Homeland Security said in a 2017 report about the mobile industry that some operators had admitted that SS7 bugs may exist. The agency was "particularly concerned that many foreign vendors appear to be sharing or selling expertise and services that can be used to spy on Americans."

"New laws and authorities may be needed to enable the government to independently assess the national security and other risks associated with SS7," the report said. In the years since, the infrastructure security gaps have largely remained open.

A blog published by security firm Secure Group in 2017 detailed how the 1970s-era SS7 protocol can be exploited to track calls, texts and movements.

It said: "The protocol is ubiquitous and connects practically all networks around the globe. Hacking into SS7 gives attackers the same capabilities as mobile operators and intelligence agencies. And in terms of surveillance, they are considerable."

Security expert Dmitry Fedotov has previously said the only tech needed to conduct such a hack is a computer, the Linux operating system and a software development kit for SS7. "Apart from the computer itself, remaining ingredients are free and publicly available on the Internet," he wrote in a blog on the flaws in January 2019.

A China Unicom spokesperson told The Guardian that it "strongly refutes the allegations that China Unicom has engaged in active surveillance attacks against U.S. mobile phone subscribers using access to international telecommunications networks."

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Stock image: Hooded man using mobile phone. A mobile security expert has accused China of exploiting cellphone networks in the Caribbean to conduct “mass surveillance” on Amerians. iStock