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Spies Can Eavesdrop By Watching a Light Bulb's Vibrations (wired.com) 71

Posted by BeauHD from the side-channel-attack dept.
An anonymous reader quotes a report from Wired: Researchers from Israeli's Ben-Gurion University of the Negev and the Weizmann Institute of Science today revealed a new technique for long-distance eavesdropping they call "lamphone." They say it allows anyone with a laptop and less than a thousand dollars of equipment -- just a telescope and a $400 electro-optical sensor -- to listen in on any sounds in a room that's hundreds of feet away in real-time, simply by observing the minuscule vibrations those sounds create on the glass surface of a light bulb inside. By measuring the tiny changes in light output from the bulb that those vibrations cause, the researchers show that a spy can pick up sound clearly enough to discern the contents of conversations or even recognize a piece of music.

In their experiments, the researchers placed a series of telescopes around 80 feet away from a target office's light bulb, and put each telescope's eyepiece in front of a Thorlabs PDA100A2 electro-optical sensor. They then used an analog-to-digital converter to convert the electrical signals from that sensor to digital information. While they played music and speech recordings in the faraway room, they fed the information picked up by their set-up to a laptop, which analyzed the readings. The researchers found that the tiny vibrations of the light bulb in response to sound -- movements that they measured at as little as a few hundred microns -- registered as a measurable changes in the light their sensor picked up through each telescope. After processing the signal through software to filter out noise, they were able to reconstruct recordings of the sounds inside the room with remarkable fidelity: They showed, for instance, that they could reproduce an audible snippet of a speech from President Donald Trump well enough for it to be transcribed by Google's Cloud Speech API. They also generated a recording of the Beatles' "Let It Be" clear enough that the name-that-tune app Shazam could instantly recognize it. There are some limitations. "In their tests, the researchers used a hanging bulb, and it's not clear if a bulb mounted in a fixed lamp or a ceiling fixture would vibrate enough to derive the same sort of audio signal," the report adds. "The voice and music recordings they used in their demonstrations were also louder than the average human conversation, with speakers turned to their maximum volume."

With that said, the teams says that "they also used a relatively cheap electro-optical sensor and analog-to-digital converter, and could have upgraded to a more expensive one to pick up quieter conversations," reports Wired. "LED bulbs also offer a signal-to-noise ratio that's about 6.3 times that of an incandescent bulb and 70 times a fluorescent one."
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Spies Can Eavesdrop By Watching a Light Bulb's Vibrations More

Spies Can Eavesdrop By Watching a Light Bulb's Vibrations

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  • childs play (Score:5, Interesting)

    by hdyoung ( 5182939 ) on Friday June 12, 2020 @07:10PM (#60177546)
    I have no personal knowledge about this, but when I was in graduate school, I had a friend who was getting a doctorate in physics. He saw a fairly simple calculation showing that you don't even need to bounce the laser off a window or a light bulb. You can probably extract sound from inside a room by just shining the right laser on the outside wall and carefully analyzing what bounces off. Right through the concrete or brick.


    If a sophisticated, well-funded, well-organized spy agency wants a specific piece of information badly enough, there really isn't much that normal chumps can do about it.

    • So, how do we secure communications against this attack? Vibrate all the walls harder than the conversation can?

      • get an anechoic chamber

      • Comment removed based on user account deletion
      • Again, I'm not a physicist and this was just a simple back-of-the-envelope calculation showing feasibility... along the lines of "3-nerds-in-a-university-hallway-scribbling-something-down" type of thing. My guess, based on my hazy memory, is that you might be able to vibrate the walls at audible frequencies, randomly and with enough amplitude to drown out the conversation. But, it would probably be so loud that it would make the building un-useable. Also, the more I think about it, I bet that sophisticated

        • An old soviet technique from the 50s was to hide a ribbon of thin metal somewhere, then bounce old fashioned radio off it to use it as a mic. When I was messing around with audio programming in college, I did some napkin calculations about how you could map out a room with control of computer speakers and mic using reflections from signal and some assumptions, plus basic math. With AI you could do it really well. And spies? Fugetaboutit. As of 2020 its probably not our conversations they are spying on from

          • https://en.wikipedia.org/wiki/... [wikipedia.org]

            A good read would also be The Spy in Moscow Station. It goes into some of the tactics and techniques that were used years ago (80's). I'm sure there is stuff these days that deal with spooky science in areas we don't really pay attention to, but Russians have shown the finesse for abusing those properties, whereas we tend to use more obvious means.

            • Re: (Score:1)

              by Alcari ( 1017246 )
              "Greetings comrade Ambassador! I bring gift from glorious motherland for you to be hanging in secret meetingroom! Is present from Stalin himself!"

      • So, how do we secure communications against this attack? Vibrate all the walls harder than the conversation can?

        I'll give you two clues. *hands you a pad and pencil*

      • Cone of Silence, duh.

      • Re: (Score:2)

        by kenh ( 9056 )
        Take the lightbulb out of the lamp? use flourescent lighting? close the blinds on the window? play music in the room? did you even try to come up with a way to defeat this type of attack...
      • Buildings which have layers outside and internal rooms. Probably random sounds and recorded talking on the outer layers would make it impossible to understand what was happening inside.

      • White noise generators. These are currently used in many federal government buildings where classified information is handled - the random noise vibrates the windows, walls, doors, whatever, obscuring the speech occurring inside.

        Or, at least, that's the theory.

    • Re: (Score:2)

      by gweihir ( 88907 )

      Not much of a surprise. You probably would need to get some moderately expensive equipment to get a good signal and write your own filters though. Still within reach of a gifted amateur.

      If a sophisticated, well-funded, well-organized spy agency wants a specific piece of information badly enough, there really isn't much that normal chumps can do about it.

      You can. Do not talk about it. Do not write it down and do not put it on any kind of computer. There is still no way to listen to human memories.

      • There is still no way to listen to human memories.

        Excellent. They still don't realize...

      • Re: (Score:1)

        by Alcari ( 1017246 )

        You can. Do not talk about it. Do not write it down and do not put it on any kind of computer. There is still no way to listen to human memories.

        Alright, you've kept the secret... but that information isn't much use if you can't use it.

    • im not sure how relative a definition childsplay is but i though researchers had been over this moz-extension://e0a88a84-1507-4e92-869e-421e2a95d309/http://www.applied-math.org/optical_tempest.pdf

  • This is old news (Score:3)

    by istartedi ( 132515 ) on Friday June 12, 2020 @07:20PM (#60177586) Journal

    This kind of passive eavesdropping has been around for decades. It's why CIA HQ has a double wall. At some point they realized operatives from the USSR had found a way to bounce an infrared laser off a window and possibly pick up conversations. I don't recall having heard if they verified that any intelligence was actually picked up that way. This passive Trojan Horse [wikipedia.org] almost certainly gathered some useful data.

    • From everything’s I’ve seen, this is easily defeated by turning on the TV, radio, music. Etc. This is a very old technique to foil eavesdroppers.

      • Another option would be to turn off the light and talk in the dark.

        • Doesn't help.

          An equivalent technique -- actually, it's arguably much better -- is to bounce a light beam (preferably IR) or laser off of any window.

          Better, because you have a much larger surface area and the vibrations should be more pronounced.

          As someone else mentioned, the technique has been around a long time. In fact an article describing how to do it for just a few dollars was published in Scientific American in the late 70s, early 80s.

          • The point of this method is that it's completely passive, all they use is a telescope and light sensor. A laser pointed at a window would be simple to detected, regardless of wavelength.

            • So... you can use the one I mentioned using reflected sunlight or even streetlight or yard lights.

              That's completely passive too.

      • One can always nullify known music/tv patterns. Best to have random noise.

        • And how would they do that? In movies and TV shows, there's magical technology that people can use but it doesn't work like that in real life. It's like the "magical zoom" that characters use to clean up a pixelated or extremely blurry photo into a clear one when in reality that photo does not clean up that well. It's the same with recorded audio. If someone is talking quietly in a room with loud background noise, it's very hard to filter out that conversation even if know exactly what the background noise

    • Re: (Score:2)

      by hey! ( 33014 )

      In US domestic law enforcement, it might have to be treated as the same as planting a bug, because of a landmark Supreme Court decision in 2001.

      In Kyllo v. United States [wikipedia.org] the cops caught a marijuana grower by using FLIR to detect his grow lamps inside his garage. They then used this information to obtain a search warrant.

      The use of technology to determine what was going on on the other side of walls freaked out Scalia, who wrote the majority opinion throwing out the evidence obtained with the warrant. The

      • Stephens: a human being *could* detect difference in heat coming off the wall by touching it.

        Hey Joe, have you caressed the side of Allan's barn lately? It feels 2C warmer than usual.

        IMHO, Stephens was full of it, and Scalia made the right call which is a weird thing to be typing.

        • Re: (Score:2)

          by hey! ( 33014 )

          Scalia assumed that infrared imaging was some exotic military technology with no common civilian applications. It turns there are lots of civilian applications, and you can buy one for about $300 at Home Depot.

          He was right to feel repulsed by the use of IR imaging to deduce what's going on behind someone's walls, but his analysis of *why* he felt that way was flawed and does not stand the test of time.

          The whole technological aspect of this is a red herring. People's right to privacy in their homes doesn't

  • I replaced all my incandescent bulbs with LED bulbs,

    Well there are 4 or 5 incandescent bulbs, but they are all outside.

  • "When you come to dwell in the light, what will you do?"

  • When going dark is really going dark.

    And yes, this is a previously-known attack against more than lightbulbs, but that's not as funny.
  • That's a few tenths of a millimeter. If the sound level is high enough to move a filament or glass envelope that much, it's probably loud enough to damage your hearing. It's hardly surprising that it modulates light.

    • Do you have calculations to back that up? Maybe you're right about the glass vibrations, but I could see a filament being very sensitive to acoustic waves - it's a thin, flexible, sometimes coiled wire.

      I'd also like to know about a lampshade effect. Basically anything between the light source and received that could modulate the light could be susceptible, like a lampshade or curtain. They say one way to mitigate this is to close the curtain, but does that open up its own means of spying?

  • CONTROL (Get Smart) was way ahead on this (Score:5, Funny)

    by Megahard ( 1053072 ) on Friday June 12, 2020 @07:37PM (#60177628)

    That's why they used the Cone of Silence.

  • Clearly the answer is not to have a hanging light bulb in the room. But if you must, and if you must leave that bulb visible to the outside world, and if you must talk about some horrible crime that's important enough to have someone spend $1,000 to spy on you, turn it off!

    Alternately you could
    - not talk about committing crimes worthy of that much spy attention in a room with the shades/blinds/curtains open
    - put the bulb into a recessed enclosure, such as is often found in offices, bathrooms, and lampshade

  • "In their tests, the researchers used a hanging bulb, and it's not clear if a bulb mounted in a fixed lamp or a ceiling fixture would vibrate enough to derive the same sort of audio signal," the report adds.

    Why not just test it? I presume the most difficult part is setting up the equipment, and once you've done that, finding a ceiling bulb is easy.

    • I'm guessing *they* could not get it to work with a fixed lamp or ceiling fixture, but they were not willing to declare it impossible.

  • This is interesting, but the simple way around it is to... dun dun duuuuun..... ...use florecent lights.

  • I doubt most speeches by Donald Trump are coherent enough to be transcribed by Google Cloud.

  • I don't understand why LEDs would work better than incandescent for this, but am NOT surprised at the vast improvement over CFLs. Florescents are extremely noisy in many respects, and should be very hard to extract this kind of signal from. So replace all the lights in your secure room with CFLs and Bob's your uncle. You might not want to stay there for long if they're the cheap cool-white ones, but that's probably a good thing - keep meeting length under control.

  • Meanwhile Palestinians languish in their prison world...
  • ... with "speakers turned to their maximum volume" (as per the article) I could probably eavesdrop without the need for telescopes, filters and software. I can hear the neighbour's kids yelling at each other from clear across the road, no problem. Even when they have their windows closed.
  • Interesting article, but as we shift to bulbs without filaments like LED or fluorescent bulbs, will this technology still work?
  • Interesting research. True, I think that there is still a lot need to be checked to come to the final conclusions. Guys can simply go to https://edubirdie.com/capstone... [edubirdie.com] if they need help continuing their research. I wonder if they will go further with this topic.

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