Find all your DIY electronics in the MakerShed. 3D Printing, Kits, Arduino, Raspberry Pi, Books & more!


In today’s New York Times article by Heather Murphy, a story was related where a group of lawyers were ordered by NSA whistleblower Edward Snowden to put their cell phones in the refrigerator before sitting down for dinner. The idea was that the metal-clad fridge would act as a Faraday cage, blocking any electromagnetic signals and preventing the group from being surveilled.

This sounded a bit dubious, since a refrigerator is not completely sealed in metal. A counter surveillance designer by the name of Adam Harvey suggested that a cocktail shaker is a much better alternative. Curiosity got the best of me, so I decided to test out both. See the video above for the results.

Michael Colombo

In addition to being an online editor for MAKE Magazine, Michael Colombo works in fabrication, electronics, sound design, music production and performance (Yes. All that.) In the past he has also been a childrens’ educator and entertainer, and holds a Masters degree from NYU’s Interactive Telecommunications Program.


Related

Comments

  1. Denbo says:

    One would imagine that the insulation would muffle the sounds (just not the radio waves),

    1. LDLB says:

      This (and the comment below at time of writing).

      It’s not news that governments can remotely activate a mobile phone and use said phone as a listening device (if you find this claim dubious, Google it). So, if one’s intention is to prevent audio eavesdropping (assuming, for example, a Bluetooth headset isn’t used, which is subject to its own limitations), use of a refrigerator would likely be sufficient.

      If a higher level of anonymity is necessary, then one can assume that ALL forms of modern electronic devices (not talking about flashlights or Arduinos here) are potentially exploitable by entities with sufficient resources/authority. And barring sufficient expertise, paranoia, and other electronic things be avoided all together…which begs the question, “What kind of serious adversary *actually* uses the services which the NSA has been tapping for sensitive communications?” The seemingly reasonable answer is, None.

  2. James Talbot says:

    I thought the whole purpose of the fridge was to prevent anyone from using their cellphone to record the meeting (and then send it on digitally whenever they want). In the fridge there is too much noise for a cellphone to record the conversation happening outside the fridge. That’s much better than a Faraday cage.

    1. Aaron Weiss says:

      Yes! We really need a second test with an audio recording running. Could you extract usable audio from a phone in the fridge?

  3. Mark A says:

    I’d have washed or moved the dishes in the sink before broadcasting the state of my kitchen to the world :-)

    1. Outer clutter is a sign of inner brilliance.

      1. Evelyn says:

        Then I must be brighter than the sun on my inside! Thanks for making me smile. I needed it today.

  4. Ken Matlock says:

    Might want to edit the video and blur out your phone number, unless you want to get lots of crank calls :)

    1. I thought about that, but given the nature of the post, I figured I’d let it all hang out there.

  5. Cody says:

    Hide your cell phone number guy.

    1. Cajun Exile says:

      The NSA already has his cell phone number so what would be the point?

  6. Gene says:

    What about inside a microwave oven?

    1. randomguy says:

      you win. can’t tell you exactly whose employ i was in when i learned that trick, but trust me when i say that a microwave is actually a technique taught to people.
      i think it might have to be plugged in (grounded) to be totally effective but i can’t recall them ever saying one way or the other.

      1. Dave Bell says:

        Apparently not (always) effective! See my post below…

    2. David Adams says:

      Yes! Microwaves are shielded to prevent microwave radiation from escaping. That shielding also prevents any microwave radiation (and mobile networks fall into this band) from entering. Put your phone in the microwave and watch it go to zero bars of signal.

      P.S. Don’t turn the microwave on! :)

      1. Steve G. says:

        Not all microwaves are created equal (or properly). Whenever I go to buy a new one I always put my phone in it even when the microwave is unplugged (expect many weird looks from sales people) shut the door and have someone text me. If my phone gets the message I move on to the next. A properly sealed microwave will block all phone signals even without being plugged in. So if your phone gets signal in any microwave it’s time to get a new microwave.

        Improperly sealed microwaves can also affect wifi and wireless internet signals (really anything running in or around the 2.4Ghz spectrum) when running.

  7. Jeff Carter says:

    Geez, just turn it off

    1. randomguy says:

      um, that isn’t nearly as effective as you might think.

  8. A microwave is best, its actually a faraday cage

  9. Evan says:

    Hey, it’s spelled Sriracha :D

  10. E field nullification is fairly easy within a Faraday cage. I wonder if the difference is not due to the much lower reluctance of the silver or chromium in the cocktail shaker as opposed to the steel in the frig. The H field nullification is dependent on eddy currents in the surround. Come to think of it – silver or chrome excel in both resistance and reluctance.

  11. Eric Hunting says:

    3M makes–or used to make–a nickel fiber based sheet material that was used under paint or wallpaper for TEMPEST-proof digital security rooms and was readily available off the shelf. By lining the walls with this material any room could be made into a faraday cage–it was developed in the CRT/CLI era when there was supposedly common snooping of monitors for key-logging. They also were once quite generous in their offers of free samples for it. Such material was quite cheap and could be easily bonded to fabrics and other materials to make faraday-cage bags and RF shielding for unusual electronics enclosures. Any simple laptop bag, briefcase, or cell phone cover could be protected with this. I recall passing my samples on to a fellow looking to start a cottage industry in microwave exposure shields for cell phones. It has also been used by people who claim EMF sensitivities and such. Any Etsy entrepreneurs looking to cash-in on the craze, give a brother a nod for the idea, OK?

    (I just realized that I was listening to the Secret Agent channel on SomaFM while writing this…)

  12. Tim says:

    Even better: Since a cocktail shaker is small enough to fit in a refrigerator, you can put your phone in a shaker to get the Faraday cage, and then put that in the fridge to get the noise muffling. Best of both worlds!

  13. John A says:

    It seems we all had similar thoughts but I don’t think the point of the fridge was anything but sound insulation. If anything else was a concern then the GPS data would already show reporters were gathering and meeting someone. It actually matches with the idea the NSA just Hoovers stuff up for later playback and analysis, once they see a reason to. At that rate I wonder how long before they start pulling feeds from every webcam and wireless baby-monitor too…

  14. Bill Marshall says:

    This is a great little demo, thanks. But I also tried putting my phone in the microwave (plugged in, not running) and was surprised that it was able to receive calls. How can that be ? Does it mean that the microwave could be leaking ? Interesting that other replies have reported the same.

  15. ka1axy says:

    Having built my own Faraday cage, I can tell you that a refrig is probably not a good choice, and the cocktail shaker will probably work well. The key is to build a completely sealed metal enclosure around the device, with no wires entering or leaving.

    If your cocktail shaker is not available (perhaps you’re preparing a martini — shaken, not stirred, of course) a cheaper solution is a plastic antistatic bag (the kind you get hard drives in). Insert the phone, and make sure to roll the open end over a couple of times and seal with a clamp. A bonus is that you can watch the “signal strength” bars as you do this.

  16. Philip Trickett says:

    OK, also , a crisp / chip packet that is made from metallised foil also works, not as well as an anti-static bag, but it still works for killing the phone signal.

  17. leif says:

    How about just removing the battery? It should be easy even without tools on any phone but an iPhone. All iPhone users need is a hammer. I suppose a good rock would do in a pinch.

  18. leif says:

    Actually, the more I think about it removing the battery is a far better solution. So long as the phone is on but can’t get a signal it will be transmitting at maximum power trying to reach the attention of a tower somewhere. This will suck your battery dry fast as well as produce lots of excess heat. I’ve seen this happen even just driving through deadspots in the country. Also, given the proximity to metal the antenna is probably detuned, the extra SWR is not good for the final amplifier of your phone transmitter.

    Just do yourself a favor and take the battery out if you need to worry about things like this!

    1. Not all cell phone batteries are (easily) removable

      1. dex drako says:

        which is just another reason to never buy an Iphone. lol

        sorry had to.

  19. Joe Roberts says:

    Maybe a lead lined older style refrigerator?

  20. Steve says:

    Most phones have the ability to turn off the GPS, cell and wifi. Why would turning them all off not work? If my phone can still be activated remotely with these functions off, then technically these functions aren’t off.

  21. Dave Bell says:

    Ran some experiments:
    1. The microwave does no good whatsoever; perhaps our seals a bad. :(
    2. Got a cast aluminum Bud Box (CU-476). Placed iPhone in it (face down), set lid on without screwing it in place. Completely blocked!
    3. Nudged lid open 1/4”. Still blocked
    4. Continued sliding the lid open, until it was completely removed. STILL blocked!
    5. Flipped iPhone face up, lid still off. Rang immediately when called.
    6. Lid fully on, blocked.
    7. Lid open 1/4”, still blocked
    8. Lid open ~1/2”, blocked for a while, but rang before it went to voicemail

    So, forget the fridge or microwave, but the (metal!!) cocktail shaker should work well.
    Or a Bud Box, that would hold 4 or 5 iPhones at a time…

    1. Dave Bell says:

      leif had a good point about battery drain and possible SWR impact on the radio.
      SO, before locking up the phone, set it to Airplane Mode and/or power off.

  22. Chris says:

    Ideally you would need a continuous conductive surface surrounding the phone, which is why the shaker would work well, also a galvanized steel trash can would be a good option. There are a lot of potential problems with the refrigerator. Since you are looking at attenuation over a specific frequency region, you may get substantially different levels of reduction with a small hotel fridge, hard to say. I’m not sure how many dBs of attenuation you would need to effectively make a phone innoperable. I think the sample size is too small to discredit the theory entirely.

  23. Draeger says:

    erm, the idea is to prevent either audio or video from being recorded either remotely or locally by placing a cell phone in a fridge – but if you want to be doubly protected from tracking and audio/video recording – put the phone in a cocktail shaker in the fridge :)

  24. Yan says:

    Would it make a different if the fridge was stainless steel?

  25. Sean Michael Ragan says:

    I find it’s best to err on the side of extreme paranoia with these things. So I recommend putting the phone in airplane mode, then turning it off, then taking out the battery, then stashing it in a cocktail shaker. Then put the cocktail shaker in the microwave and the microwave in the fridge. Then leave the house and drive to another state. And you should be good.

  26. So how many people have called or texted you since your phone number is in the video ;p

    1. zero, despite 60k views on Youtube. I’d like to think they’re respectful of privacy :)

  27. john says:

    You should try with a stainless steel fridge just to be sure.

    1. BunE22 says:

      Sorry I’m replying so late, I just found this site. I tried my microwave, the phone had signal and rang. Tried my stainless steel SubZero fridge, phone still rang. Tried my Sears side by side fridge (yeah I have 2 the SubZ is too small), the phone still rang. Tried my washing machine, it rang. But it didn’t ring in the dryer! And I had no missed call on the log either.

  28. bill says:

    if you have an all metal building–maybe with concrete floor–would it act as a faraday box for car/battery/radios/ electronic equipt. in case of disturbance? maybe if building was heavily grounded & you insulate materials from the floor & building? how about a metal filing cabinet?

  29. Johnny108 says:

    You can use an empty bag of chips with a mylar liner to block a cell phone. Put your phone in a plastic bag, or wrap it in a paper towel (to keep chip grease off of the phone, and to keep the phone’s antenna from touching the mylar), and put it in an empty Cheetos, or Doritos bag, roll the open end closed, and clip it with any kind of clip. It won’t send or receive.

  30. Ed says:

    You guys are missing the bigger picture. The whole reason to need a Faraday cage is to act as defense against an EMP blast. The EMP from a Carrington type solar flare is a different threat than the EMP from high up nukes.

    A galvanized can is actually a good Faraday cage, given that the lid is securely fitting all the way around. Also, it is CRITICAL to insulate your device from the material of the cage, so naturally the best way to ‘harden’ something is to have it in Russian nested doll style cage/insulation/cage etc…

    Everyone needs to read the novel ‘One Second After’ if you want the chilling truth about the largest threat hanging over USA. Two little nukes above the continental States would render inert ALL inetegrated circuitry useless. Even the U.S. military has a mere handful of hardened Humvee’s and armoured vehicles of various type… At last count they only had 2 planes, both F16′s, that were so heavy they could no longer carry armaments.

    Here is the list of things you need in a Faraday cage:

    – Two extra sets of all IC gadgets out of whatever car you drive. If you drive a Dusenberg, don’t worry it will still fire up after North Korea turns the US into a Colonial re-creation. Otherwise, you need a vehicle from the 80′s where a handful of little boxes and the alternator were the only thing with IC onboard, and get backup parts for each. Congrats, you will be the only one in thousands of miles with a working car the next morning. (hint: duck)

    – Your smartphone and several batteries, as well as a battery charger. No, the phone won’t work: but the gigabytes of information and books and manuals will all be there, on a working handheld computer. Batteries have circuitry in them as well, so… Obviously you have several dynamo chargers and solar panel power distribution cards in there too – duh.

    – 2 way FRS radios, of course. Several sets of them. Also a few small short-wave radios.

    – Tactical flashlights. Normal flashlights will all still work, but if you are packing 950 Lumens you have a decided tactical advantage. Make no mistake, the strobe on these at close range is a serious weapon. For 18650 class toss the charger in the garbage can too.

    – Tasers, stun guns, batons with 60kv sharp prods… Naturally these live in the cans. Non lethal close range self defense is key to surviving the post Crash wasteland.

    – Original GameBoy, with Tetris and all the Super Mario games. Hey, the emulators for phones still aren’t as good as the real thing.

  31. jt says:

    I used a medium sized coffee can, wrapped in foil, upside down with my HTC One inside, resting on 4 single sheets of foil. Didn’t ring at all.

  32. Great victory Edward Snowden !!

    This is the awesome news you have provided. Is there any possibility to view all these in practical life ?? It’s such a wonderful invention.

    Hopefully you will provide me the answer.

    Thanks