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Sheet could shelter Wi-Fi from eavesdroppers

Wireless hackers, beware--this window treatment is meant to keep Wi-Fi signals in and you out.

Wireless hackers in the United Kingdom could soon face a new obstacle to stealing information.

The British government has endorsed a transparent film that can block Wi-Fi transmissions and other wireless signals from traveling through windows.

The film, called SpyGuard, can be laminated or fitted inside windows to prevent remote eavesdroppers from penetrating rooms with infrared or Wi-Fi signals to steal information or access private networks.

To stop Wi-Fi signals "leaking" from a room, the walls are also covered with a layer of paint that contains the same metals as the SpyGuard film. The film can even prevent hackers from stealing information from the light flicker emitted from computer monitors and reflected on a window, claims GlassLock UK, a company that sells the film in Britain.

"The film is developed by the U.S. National Security Agency," said John Hall, managing director of GlassLock UK. "The only way you can get hold of it here is through us."

CESG (Communications-Electronics Security Group), the information assurance arm of the U.K. Government Communications Headquarters, has backed the product, but the intelligence community is keeping an eye on who buys it.

"We have to get permission to sell it," said Hall. "We have to tell MI5 who we sell it to. It's no problem unless they're known terrorists."

GlassLock is demonstrating the product at Infosecurity Europe 2005 in London. The exhibition ends Thursday.

Dan Ilett of ZDNet UK reported from London.