LASER BEAM EAVESDROPPING Kevin Murray has provided us with the results of their testing of laser beam eavesdropping systems. It is of intense interest to many, so we'll provide a reasonably complete summary in this letter. (If you want an original of his report, I'm sure he'll be pleased to oblige. Write him at Kevin D. Murray Associates, POB 5004, Clinton, NJ 08809 or call 800-635-0811.) Here's his report. ------------------------------------------------------------------------------- Laser Beam Eavesdropping Summary. Does it exist? Yes. We designed, built, and tested a complete working system. Does it work? Yes. The technique works very well under laboratory conditions. Is it a threat? No. Due to operational limitations under field conditions, we are not reporting this as a threat to the majority of clients at this time. Sci-Fi Bugs? Eavesdrop from afar, merely by pointing at a window. The idea is alluring to some, horrific to others. News media reports of just such a bugging device, based on laser beam technology, have been circulating for some time now. A litany of claims "...can hear from miles away..." and compound claims "...through closed windows...", culminates with the coda "No one is safe." Like the X-Ray vision glasses of comic book fame, the claims tend to become exaggerated. But, unlike the concept of X-Ray vision, laser listening can be accomplished with the right equipment and conditions. A Century Old Invention. April 26th, 1880 - Alexander Graham Bell & Sumner Tainter announce their invention - the Photophone. Sound transmitted on reflected light rays a distance of 213 meters. They also claim, "It can transmit songs with great clarity of tone." This is the forerunner of CD record players, fiber optic telephone transmission, and remote eavesdropping. It's Greek to them, Diogenes. We researched this threat for our clients and heard much speculation from the pundits, conjecture from dilettantes, and hyperbole from the media. In most cases, the "experts" had never even seen a laser bug. They were running on grapevine knowledge. We Built Our Own. Using assembly plans available to the general public, we built a laser receiving system (Radio/Electronics 10/87). For aiming and safety reasons, a visible laser beam was used in our tests (Spectra Physics Inc. - 10 mW linear Helium-Neon type). Additional experiments with: optical processing, and professional audio processing, were conducted. These results, and allowances for more sophisticated receiver circuitry, were factored into our test results. Physics 101 (Simplified.) Sound is transmitted by vibration. When you speak, you vibrate the air. The air, in turn, vibrates everything it contacts. Certain objects, e.g., windows and mirrors, pick up vibrations very easily. When a laser light beam hits such an object, it `vibrates' also as it reflects and continues its trip. The reflected `vibrating' beam can be received, electronically processed, and the audio listened to. Under controlled conditions, high quality audio can be recovered. Physics 202 (The Real World.) Bouncing an invisible laser beam off a window, and attempting to catch the reflection, is a little like playing 3-D billiards, blindfolded. The fun increases exponentially with distance from the target. All sound will vibrate a window. This includes interior conversations as well as exterior noises (cars, trucks, birds, etc.) Our audio laboratory processing equipment could attenuate this effect, to a degree. The rule of thumb seems to be, if the outside noise is as loud as the conversation, audio processing techniques are of marginal assistance. Reflecting a beam off interior objects helps reduce external sound. The beam, however, loses power with each pane of glass it passes through. This reduces effective working distances and increases the number of reflected beams with which one must cope. Thick glass and thermo-pane glass, as used in office buildings, do not conduct sound vibrations well. Air thermals and wind, disrupt laser beams. The greater the beam length, the greater the disruption. Wind blowing through a laser beam generates noise similar to the cacophony of 747 engines. A laser beam (one powerful enough for professional eavesdropping) is the Neutron Bomb equivalent of a sharp stick in the eye. Both can blind you, but the laser leaves the eye standing. Blinding the subject of a surveillance is not the best way of assuring a continued stream of information while remaining unnoticed. We used safety goggles during our tests. "There must be better ways to eavesdrop and spy", I hear you say. There are. "Beat the Beam" Countermeasures Course If you suspect a laser beam eavesdropping attempt is being made against you, use one of the following techniques: Hold confidential conversations in a room without windows. Place a radio against the window and close the drapes. Install a white noise generator on the window pane. In addition, do not discuss your suspicions in the sensitive area. Contact an independent information security consultant for additional assistance. Your problem is more extensive than you think.