Window film shields against electronic spying

A report in Scientific American.com says that a film for windows that can block wireless electronic signals is now declassified and being manufactured in Virginia.
The Llumar Signal Defense Security Film is a coating of about two-1000ths of an inch thick. Once applied to windows it can prevent shattering from projectiles, but also prevent espionage of electronic information through the windows of a building.
Interviewed for the report, dated June 26, Lisa Winckler, global director of research and technology at the manufacturer, the film can shield against signals across a wide swath of the electromagnetic spectrum, including transmissions in the near infrared or terahertz range. It could not only prevent eavesdropping on wireless electronic data, but also might be used to prevent electronic chatter and interference as more and more electronic devices are being used.
A similar security window film is believed to have been used on the Pentagon and helped to prevent the windows shattering when they were hit on September 11, 2001. Now the formula has been declassified, the manufacturer, CPFilms in Martinsville, Virginia, is making it available to the general market as part of an all-inclusive package of technology, but one that reportedly carries a very high price.