WASHINGTON, Dec 3 (Reuters) - A senior U.S. official who

is among those working to evict alleged Chinese hackers from

American telecom companies has a word of advice for his fellow

Americans:

Use encryption.

During a call with reporters on Tuesday, Cybersecurity and

Infrastructure Security Agency official Jeff Greene said

Americans should know that "encryption is your friend" and that

"our advice is to avoid using plaintext."

Although it is not the first time a senior American official

has endorsed encryption, a data-scrambling technique that helps

protect communications from snoopers, it is a stark break with

previous government messaging.

Only a few years ago, FBI Director Chris Wray described

strong encryption as "an urgent public safety issue" amid a push

by law enforcement officials to mandate that tech companies

water down the protections around digital communications.

Greene's call with journalists was held as the government

issued guidance for combating allegedly Chinese intrusions into

U.S. telecoms.

Washington has voiced increasing concern over Beijing's

alleged efforts to burrow deep into U.S. telecommunications

companies, including T-Mobile, and steal data about U.S. calls.

U.S. officials have previously alleged that the hackers

stole telephone audio intercepts, along with a large tranche of

call record data. Officials have said those records mainly

concerned people in the Washington area.

Chinese officials have previously described the allegations

as disinformation and that Beijing "firmly opposes and combats

cyber attacks and cyber theft in all forms."

Greene's advice to switch to encrypted calls and messaging -

which is offered by apps such as Meta Platform's

WhatsApp and the privacy-focused service Signal - is a sign that

the agency believes that Chinese hackers may be lurking in

telecom companies' networks for some time yet.

Greene, who serves as CISA's Executive Assistant Director

for Cybersecurity, said as much when asked about a timetable for

kicking the hackers out of America's telecom networks.

"It would be impossible for us to predict when we'll have

full eviction," he said.