(CBS)  U.S. intelligence officials issued a strong warning Thursday that Americans traveling overseas, particularly visitors to the Olympics in China, face a serious risk of having sensitive information stolen, reports CBS News correspondent Bob Orr.

The travel alert is blunt:

"All information you send electronically - by fax machine, personal digital assistant (PDA), computer or telephone - can be intercepted."

In an exclusive interview with CBS News, Joel Brenner, the government's top cyber-security official, urged Americans to leave all devices at home.

"Somebody with a wirless device in China should expect it to be compromised while he's there," Brenner said.

And those who must take phones and BlackBerries with them should remove the batteries.

"The public security services in China can turn your telephone on and activate its microphone when you think it's off," said Brenner.

China is one of a number of countries pushing active cyber-espionage programs aimed primarily at cracking U.S. national security computers and stealing corporate trade secrets. Billions have already been lost.

In addition, cyber-gangs and criminals, many based in Asia, have stolen bank accounts and credit card numbers from an untold number of Americans.

For protection, Brenner's office says, travelers should frequently change passwords, update anti-virus and spyware protections and avoid wireless or WiFi networks when possible. (In some countries they're controlled by state security forces.) The fear is compromised mobile devices give thieves open access to all of your computer files back home.

"We are giving advice based on a pattern that is relentless and ongoing as what we see as information theft," said Brenner.

And the government says no overseas traveler should discount the threat. Don't assume, the bulletin warns, that you're not important enough to be targeted.