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


Forgot your password?
Wireless Networking Communications Network Networking Privacy Security Technology

Stray WiFi Signals Could Let Spies See Inside Closed Rooms (sciencemag.org) 41

sciencehabit quotes a report from Science Magazine: Your wireless router may be giving you away in a manner you never dreamed of. For the first time, physicists have used radio waves from a Wi-Fi transmitter to encode a 3D image of a real object in a hologram similar to the image of Princess Leia projected by R2D2 in the movie Star Wars. In principle, the technique could enable outsiders to "see" the inside of a room using only the Wi-Fi signals leaking out of it, although some researchers say such spying may be easier said than done. Their experiment relies on none of the billions of digital bits of information encoded in Wi-Fi signals, just the fact that the signals are clean, "coherent" waves. However, instead of recording the key interference pattern on a photographic plate, the researchers record it with a Wi-Fi receiver and reconstruct the object in a computer. They placed a Wi-Fi transmitter in a room, 0.9 meters behind the cross. Then they placed a standard Wi-Fi receiver 1.4 meters in front of the cross and moved it slowly back and forth to map out a "virtual screen" that substituted for the photographic plate. Also, instead of having a separate reference beam coming straight to the screen, they placed a second, stationary receiver a few meters away, where it had a direct view of the emitter. For each point on the virtual screen, the researchers compared the signals arriving simultaneously at both receivers, and made a hologram by mapping the delays caused by the aluminum cross. The virtual hologram isn't exactly like a traditional one, as researchers can't recover the image of the object by shining more radio waves on it. Instead, the scientists used the computer to run the radio waves backward in time from the screen to the distance where wave fronts hit the object. The cross then popped out.
This discussion has been archived. No new comments can be posted.

Stray WiFi Signals Could Let Spies See Inside Closed Rooms

Comments Filter:
  • by Anonymous Coward

    2013: http://m.slashdot.org/story/188149
    2009: http://m.slashdot.org/story/125417

    How long until someone else "discovers" the same thing again?

  • by Gravis Zero ( 934156 ) on Saturday April 29, 2017 @06:43AM (#54324431)

    What this is really showing is that they have worked out how to make an array antenna and composite that data to "see" what is blocking RF signals which is normally metals. I think you would be hardpressed to identify if a person was standing in the room. Still interesting though.

    • by asylumx ( 881307 )
      Yes, very interesting. Not sure why they are marketing it with the fear of spies! It's already cool tech; it seems like the article could stand on its own without the need for drama.
    • Yep. And the only interference it can "see" is that of metal. And only a certain distance. And only if it is still for a long time.

    • I think you would be hardpressed to identify if a person was standing in the room

      Unless they are wearing their tinfoil hat. Think about it...

      • by Anonymous Coward

        Oh, crap - they can ONLY see my if I wear my tinfoil hat !
        But if I take it off...
        But if I...

        NO CARRIER

    • Well, it would work on Wolverine.

  • What is next? They can use "light waves" to detect a cross placed in a room? Its like magic and stuff!
  • They basically took a CT scan (computed tomography) using radio waves instead of x-rays.

    Tomography [wikipedia.org] has been around for over 80 years. It's why there's no lens when you have a traditional x-ray taken. You just fire the RF rays in a uniform direction (in this case the single WiFi course acts as a point source with all rays radiating radially), and capture them using a flat photographic plate (or in this case, by moving the WiFi receiver around on a plane). What they're doing isn't even as sophisticated
  • Sounds a little more fancy in the implementation, but using wifi as a passive radar isn't a new idea.

    https://www.extremetech.com/ex... [extremetech.com]

  • If this were true it could possibly get rid of MRI's.

System checkpoint complete.