Chinese Hackers Are Said to Have Targeted Phones Used by Trump and Vance

Chinese hackers who are believed to have burrowed deep into American communications networks targeted data from phones used by former President Donald J. Trump and his running mate, Senator JD Vance of Ohio, people familiar with the matter said on Friday.

Investigators are working to determine what communications data, if any, was taken or observed by the sophisticated penetration of telecom systems, according to these people, who spoke on the condition of anonymity to describe an active and highly sensitive national security case.

The type of information on phones used by a presidential candidate and his running mate could be a gold mine for an intelligence agency: Who they called and texted, how often they communicated with certain people, and how long they talked to those people could be highly valuable to an adversary like China. That sort of communications data could be even more useful if hackers could observe it in real time.

The Trump campaign team was made aware this week that the Republican presidential nominee and his running mate were among a number of people inside and outside of government whose phone numbers had been targeted through the infiltration of Verizon phone systems, the officials said.

It was unclear whether the hackers could have gained access to text messages, especially those sent through unencrypted channels.

Data about the communications of a presidential and vice-presidential candidate — even absent the content of the calls and messages — could also help an adversary like China better identify and target people in Mr. Trump’s inner circle for influence operations.