Two American telecom companies, AT&T and Verizon, have confirmed the security of their U.S. networks following cyber espionage attempts linked to the Chinese-backed Salt Typhoon operation.

AT&T, the telecommunications giant, has taken urgent action to reset millions of customer account passcodes following a significant data breach where a cache of data consisting of AT&T customer records surfaced online earlier this month, according to TechCrunch, an American global online newspaper.