Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?
Privacy Science

Snooping Through Walls with Microwaves 217

denis-The-menace writes "According to an article from newscientist, scientists have devised a system to use microwave energy for surveillance. If people are speaking inside the room, any flimsy surface, such as clothing, will be vibrating. This modulates the radio beam reflected from the surface. Although the radio reflection that passes back through the wall is extremely faint, the kind of electronic extraction and signal cleaning tricks used by NASA to decode signals in space can be used to extract speech. Although, I doubt it would work in this room"
This discussion has been archived. No new comments can be posted.

Snooping Through Walls with Microwaves

Comments Filter:
  • Re:Invest in AA (Score:4, Informative)

    by Anonymous Coward on Wednesday October 26, 2005 @06:37AM (#13879263)
    Aside from the fact that farmers and subsidies have all but shut down Alcoa in the US, Aluminum is a poor choice, and hence wouldn't be used. Lead. That would be the metal of choice. It has properties which make it excellent at sound proofing. Vibrating aluminum would modulate their signal quite nicely.
  • Not new tech (Score:4, Informative)

    by Anonymous Coward on Wednesday October 26, 2005 @06:39AM (#13879267)
    I don't think this a new technology. I think that this is just a new take on a technology that Léon Theremin (inventor of the Theremin instrument) was working on for the KGB in the 50-60s. He was using infrared bounced off of windows to detect conversations inside (or something). http://en.wikipedia.org/wiki/L [wikipedia.org]éon_Theremin
  • Fluff piece (Score:5, Informative)

    by gtoomey ( 528943 ) on Wednesday October 26, 2005 @06:42AM (#13879277)
    This "story" is just a reference to a patent application [uspto.gov].

    Even at 100GHz, the wavelength of microwaves is 3 mm. But sound waves inside a room would cause a surface to vibrate perhaps 0.001 mm. You cant modulate a 3mm wave to record 0.001 mm changes.

  • Very dangerous!!! (Score:4, Informative)

    by elgatozorbas ( 783538 ) on Wednesday October 26, 2005 @07:13AM (#13879359)
    The summary mentioned microwave ovens, so some may be tempted to play around with a DIY radar. Don't!!! Of all domectic appliances a microwave is about the most dangerous to take apart. The RF radiation has a very high power and is invisible. When exposed to the electromagnetic field, currents start to flow inside the human body (mostly close to the skin) giving rise to burn-like wounds. Especially the risk of eye injury is significant. Don't try this at home.
  • by ettlz ( 639203 ) on Wednesday October 26, 2005 @07:31AM (#13879414) Journal
    I didn't think that sort of evidence was admissible in a UK court.
  • Foil Room fallacy (Score:3, Informative)

    by obfuscated ( 258084 ) on Wednesday October 26, 2005 @07:42AM (#13879442) Homepage
    The "Foil Room" won't help against snooping as you'd like to believe. (Prepare to ditch all your foil hats!!).

    To truly block signals, you'd need to build a actual Faraday "cage" built with the smallest possible 'holes' so the waves created inside (be it voice, the sound of you typing or even waves emitted by the blinking LED from your Ethernet card) will be cancelled out. This is the same technology that the intelligence agencies employ against counter intelligence. That with foil (which is properly grounded) will work.

    Solid surfaces such as foil can actually act as large AMPLIFIERS if implemented incorrectly since the waves will

    Note that your microwave is surrounded by a Faraday cage to protect you from the rays; not foil.

    A quick Google to back up my post yielded this page [montalk.net] discussing similar topics.
  • Not quite microwave (Score:4, Informative)

    by Ge10 ( 803950 ) on Wednesday October 26, 2005 @07:56AM (#13879487)
    This has been around for a long time. In the book "Spycatcher" by ex-MI5 agent Peter Wright, he describes a bug used by the KGB to spy on the American ambassador in Hawaii (I think). There was a metal membrane hidden inside a wooden carving, which would passively vibrate with sounds in the room. A strong RF beam of around 900 MHz (details are hazy again, and it's not quite microwave) was directed towards the office from a fair distance away, then the signal would be minutely modulated and reflected by the metal membrane. It was able to work for several years, and this was in the 1960's. You can only guess what's available now.
  • Re:Invest in AA (Score:5, Informative)

    by mikiN ( 75494 ) on Wednesday October 26, 2005 @08:02AM (#13879506)
    There is no such thing as the English language. There are, however, at least two widely spoken dialects, both of which use different spellings for the word aluminium [wikipedia.org].
  • by kilodelta ( 843627 ) on Wednesday October 26, 2005 @08:02AM (#13879507) Homepage
    I guarantee they're using a MASER. You can thank RADAR pioneers from M.I.T. and Bell Labs for that.

    That being said it is easily defeated. For example - short wavelengths below 1cm start resonating with water vapor. That's why doppler radar has been such a boon to meteorology.

    But there are ways to stop it. Metal impregnated and grounded cement walls that are, oh, 6 to 8 feet below grade level would be reasonably safe. Of course don't put any windows, just ventilation.

    And if you're really that much of a target they'd bug the place before they resorted to using microwave to listen in. BTW, for a good fantasy view of using microwave to peek in I highly recommend watching "The Siege" with Denzel Washinton and Tony Shaloub.
  • by stupid_is ( 716292 ) on Wednesday October 26, 2005 @08:03AM (#13879516) Homepage
    Google it and there's lots of site who're convinced he did. Granted that some of the origins seem to stem from an unsubstantiated chain mail, but he did seem to come up with all sorts of soundbyte gems.

    Here [quotationspage.com] is one such site.

  • Re:Invest in AA (Score:3, Informative)

    by Anonymous Coward on Wednesday October 26, 2005 @08:05AM (#13879524)
    The element was discovered by an American who named it Aluminum. The British rejected this and gave it the name Aluminium for their usage (so it would end in "ium" just like HeliUM, LithIUM, BerrylIUM, etc). Aluminum is the standard American spelling. Aluminium is the standard spelling in British Commonwealth countries. While I appreciate the British desire for consistency, the Americans can legitimately argue that the person who discovered it should be able to name it whatever they bloody well want.

    I say this as an Australian.
  • old hat (Score:2, Informative)

    by fliptout ( 9217 ) on Wednesday October 26, 2005 @08:07AM (#13879535) Homepage
    The president at one of my former companies was a colonel in the Army Security Agency. He used to tell me all sorts of things, including how the Russians bombarded the US embassy with radiation to get signature signals back. And this was in the 60s or before. The surveillance technology available to intelligence now must be quite interesting.
  • by rhkaloge ( 208983 ) on Wednesday October 26, 2005 @08:07AM (#13879537)
    I actually know researchers who have been working with what they call "wall penatrating RADAR" and it sounds a lot like this - it more detects movement and sound then being able to image what is in a room. The big things they claim it would be good for is detecting fires from a distance, finding people trapped in places (it can detect a heartbeat) and, yes, seeing that sniper around the corner. I don't think they considered audio survallence, or at least they never told us about it. But I suppose once you have a patent, you can use the tech for any purpose, noble or sinister.
  • by jhhl ( 513935 ) on Wednesday October 26, 2005 @08:58AM (#13879790) Homepage
    You are (are you?) probably talking about Microwave Impulse Radar, the miracle technology that was supposed to change our lives years ago. It's tiny bursts of microwave radar, able to be transmitted/received at short ranges at tiny power levels by an on-chip transmitter.
    Here's a typical article about MIR [llnl.gov]. Last I read, there were legal battles about shoddy treatment of potential vendors by the LLNL. Slashdot readers would probably do well to track this technology!

    A taste of this from http://www.eurekalert.org/features/doe/2004-09/dln l-etu091604.php [eurekalert.org]

    UWB's data capacity, speed, low power requirements, and resistance to interference have attracted the attention of major electronic corporations who recognize the technology's commercial potential. Because UWB can penetrate walls, it could become the center of all communications within homes and small offices. UWB signals could carry voice, data, and video. Products could speed downloading images from a digital camera to a computer, connecting printers to computers, and routing high-definition signals to televisions. The Federal Communications Commission (FCC) currently restricts commercial UWB applications to between 3.1 and 10.6 gigahertz because of a concern they could interfere with existing transmissions, especially flight radios, beacons, and the Global Positioning System. FCC rules also limit UWB commercial devices to less than 1 watt, which prevents them from working beyond a relatively short distance (about 10 meters).

    Using an experimental license, Livermore has developed numerous UWB systems in frequency bands ranging from 200 megahertz to 100 gigahertz. Tests at Livermore have shown that the devices do not cause undue interference with other electronic devices operating in this broad frequency range. Livermore efforts are directed at developing UWB devices for the government that operate both above and below the 3.1- to 10.6-gigahertz band designated for commercial devices.
  • Old news (Score:4, Informative)

    by Technician ( 215283 ) on Wednesday October 26, 2005 @09:22AM (#13879950)
    A wodden copy of the Great Seal of the United States was bugged. Part of the seal was used as a diaphram and was used as a passive resonant reflector. This would pass most bug sweeps as the device was not active, but passive. When painted with a 330 Mhz signal, it would modulate it.

    The only update in the article is now they use microwaves and common materials already in a room.

    Details here;
    http://www.spybusters.com/Great_Seal_Bug.html [spybusters.com]

    This bug is was delivered in 1946 and discovered in 1952.
  • Tin Foil Hat Designs (Score:3, Informative)

    by Mr_Perl ( 142164 ) on Wednesday October 26, 2005 @09:58AM (#13880164) Homepage
    Greetings, You may feel free to borrow my design [darkpoetry.com]:
  • Re:Fluff piece (Score:1, Informative)

    by Anonymous Coward on Wednesday October 26, 2005 @11:39AM (#13881093)
    There's an anecdote in the engineering field: where some poor sods at Racal-Dana had a phase detector at 50MHz that was so sensitive to vibration they had to stop their experiments whenever a plane took off from Orange County Airport (quite a few miles away). They eventually had to get special thick aluminum wall castings to enclose the phase detector to block the vibrations.

    That anecdote is most certainly false. First, the phase detector merely responds to the difference in phase between two signals. Any vibrations will have negligible effect on the phase difference.

    Second, encasing the circuit in a heavy aluminum block will not have any effect on vibrations. They will still pass through the aluminum. In order to provide isolation, the circuit has to be mounted on vibration isolators, such as used for old-style turntables, or simple rubber tires.

    Third, the vibration caused by an airplane taking off miles away is much less than ordinary street traffic, or even by people walking around in the building. Again, the vibration won't cause any change in the phase of the incoming signals, and placing the circuit in a aluminum block will have no effect on the output.

    Fourth, the sensitivity of the phase detector is limited by ordinary thermal noise generated in the electronics. This means the circuit most certainly cannot have the sensitivity needed to detect the low level vibrations from an airplane miles away.

    Fifth, I have been developing sensitive phase detectors since 1969, and have received a number of patents in phase detectors and related support circuitry. I can assure you that ordinary system noise makes it impossible to detect vibrations from airplanes taking off miles away.

    So the anecdote is false. Don't believe everything you hear.

    Mike Monett
  • by Ungrounded Lightning ( 62228 ) on Wednesday October 26, 2005 @05:55PM (#13884545) Journal
    Consisted of a cavity resonator ...

    Oh, yes. They also did one on that pattern that was disguised as an olive-on-a-toothpick, to put in a martini glass and carry around or leave sitting about at embassy parties.

    And the diode trick also turns anything with a diode in it into a bug.

"An open mind has but one disadvantage: it collects dirt." -- a saying at RPI