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

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.

MORE: Cellphone of Trump’s lead defense attorney compromised by Chinese hackers, sources say

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 …