Hackers with links to China breached U.S. telecommunication providers to access wiretap systems used by law enforcement.
AT&T, Lumen, and Verizon are among the telecom providers whose networks were breached.
The breaches led to the theft of customer call records data and compromised private communications of a limited number of individuals involved in government or political activity.
The hacking campaign, conducted by a China-linked group named 'Salt Typhoon,' also involved copying information subject to U.S. law enforcement requests.