Chinese hacking effort is far more pervasive than previously reported, sources say

The Chinese effort to hack prominent Americans is far more pervasive than previously reported, ABC News has learned.

Sources told ABC News that U.S. law enforcement and intelligence officials are concerned the espionage operation by the Chinese government may have been in place for well over a year -- and perhaps longer -- before it was recently discovered.

The Chinese appear to have been able to gather large volumes of data in a sweeping covert campaign targeting the cellphones and mobile devices of business leaders and other high profile Americans of both political parties, according to sources familiar with the investigation.

The evidence is mounting that in some cases the Chinese operation was able to tap into, or get access to, what cellphone users of Verizon, AT&T and Lumen were communicating.

Authorities are trying to determine whether the Chinese were able to listen to conversations and watch text messages in real time, as they were occurring, or if they captured the material for review at a later time.

Sources said that U.S. officials are only beginning to understand the breadth of the Chinese operation, but what they have found so far is deeply concerning and represents a massive breach of privacy on a disturbing scale.

The targets have included not only former President Donald Trump and Sen. JD Vance, but also individuals working in a number of government agencies.

The FBI is systematically contacting victims, sources said.

Salt Typhoon, the name given to an advanced, persistent threat actor run by the Chinese government, is believed to be behind the operation.

Intelligence officials suspect Salt Typhoon hackers exploited routers as a gateway to cellphones and mobile devices, and there is concern that Chinese capabilities for intrusion may have made significant advances.

In a statement issued last month, Verizon representatives said, "We are aware that a highly sophisticated nation-state actor has reportedly targeted several U.S. telecommunications providers to gather intelligence. Along with federal law enforcement, industry peers and third-party cyber experts, we have been and are working to confirm, assess and remediate any potential impact. Verizon is committed to assisting law enforcement in this investigation."

Representatives for AT&T and Lumen declined to comment.