WASHINGTON, Dec 18 (Reuters) - The U.S. cybersecurity

watchdog CISA is telling senior American government officials

and politicians to immediately switch to end-to-end encrypted

messaging following intrusions at major American telecoms blamed

on Chinese hackers.

In written guidance released on Wednesday, the Cybersecurity

and Infrastructure Security Agency said "individuals who are in

senior government or senior political positions" should

"immediately review and apply" a series of best practices around

the use of mobile devices.

The first recommendation: "Use only end-to-end encrypted

communications."

End-to-end encryption - a data protection technique which

aims to make data unreadable by anyone except its sender and its

recipient - is baked into various chat apps, including Meta

Platforms' ( META ) WhatsApp, Apple's ( AAPL ) iMessage, and the

privacy-focused app Signal. Corporate offerings which allow

end-to-end encryption also include Microsoft's ( MSFT ) Teams

and Zoom Communications' ( ZM ) meetings.

CISA's message is the latest in a series of increasingly

stark warnings issued by American officials in the wake of

dramatic hacks of U.S. telecom companies by a group dubbed "Salt

Typhoon."

Last week, Democratic Senator Ben Ray Lujan said that, "this

attack likely represents the largest telecommunications hack in

our nation's history."

U.S. officials have blamed China for the hacking. Beijing

routinely denies allegations of cyberespionage.