Hackers believed to be backed by China’s government have infiltrated the cellular networks of at least 10 global carriers, swiping users’ whereabouts, text-messaging records and call logs, according to a new report, amid growing scrutiny of Beijing’s cyberoffensives.

The multiyear campaign, which is continuing, targeted 20 military officials, dissidents, spies and law enforcement—all believed to be tied to China—and spanned Asia, Europe, Africa and the Middle East, says Cybereason Inc., a Boston-based cybersecurity firm that first identified the attacks. The tracked activity in the report occurred in 2018.

The cyberoffensive casts a spotlight on a Chinese group called APT 10; two of its alleged members were indicted by the U.S. Department of Justice in December for broad-ranging hacks against Western businesses and government agencies. Cybereason said the digital fingerprints left in the telecom hacks pointed to APT 10 or a threat actor sharing its methods.

“We never heard of this kind of mass-scale espionage ability to track any person across different countries,” said Cybereason Chief Executive Lior Div.