Life in a faraday cage

There was an internal discussion about an unrelated topic recently, and it reminded me of an early experience in my career at Microsoft.

When I started, my 2nd computer was a pre-production PC/AT (the first was an XT). The AT had been announced by IBM about a week before I started, so our pre-production units were allowed to be given to other MS employees (since I had to write the disk drivers for that machine, it made sense for me to own one of them).

Before I got the machine, however, it was kept in a room that we semi-affectionately called "the fishtank" (it was the room where we kept the Salmons (the code name for the PC/AT)).

IBM insisted that we keep all the pre-production computers we received from them in this room - why?

Two reasons.  The first was that there was a separate lock on the door that would limit access to the room.

The other reason was that IBM had insisted that we build a faraday cage around the room.  They were concerned that some n'er-do-well would use the RF emissions from the computer (and monitor) to read the contents of the screen and RAM.  I was told that they had technology that would allow them to read the contents of an individual screen from across the street, and they were worried about others being able to do the same thing.

Someone at work passed this link along to a research paper by Wim van Eyk that discusses the technical details behind the technology.

Comments

• Anonymous
  August 05, 2005
  Cryptonomicon delves heavily into van Eck phreaking (a little too heavily for my tastes) and the average teen geek that read it probably believes it's commonly done by every 3-letter agency in the world.
  
  IIRC, the best way to defeat it is simply to use aliased fonts, and with the advent of near-ubiquitious LCDs I'd wager that it's harder than ever to actually mount a successful van Eck attack.

• Anonymous
  August 05, 2005
  The comment has been removed

• Anonymous
  August 05, 2005
  The comment has been removed

• Anonymous
  August 05, 2005
  Jonathan, you can't build a faraday cage and have windows...
  
  THe only opening in the cage was the door (which was wooden). There was chicken wire inside the walls surrounding the room, and the ceiling tiles were constructed to ensure that people couldn't come over the top of the wall.
  

• Anonymous
  August 05, 2005
  "you can't build a faraday cage and have windows"
  
  Why not? You can build a free-standing Faraday in a room with windows, or if you're embedding the cage in the walls of the room you can also embed the mesh inside a sheet of glass (or between two sheets, which is probably easier)...

• Anonymous
  August 05, 2005
  Oh, and can I be picky and ask you to give Faraday a capital F? (Hey, don't blame me, you're the one who started complaining about poor English yesterday. That's the trouble with pedantry -- it comes back to haunt you sooner or later... :D)

• Anonymous
  August 05, 2005
  Here's a link from the Wayback machine:
  
  http://web.archive.org/web/20040811035751/http://www.shmoo.com/tempest/emr.pdf

• Anonymous
  August 05, 2005
  The lunatics on MythBusters built a Faraday cage, which successfully made a cell phone go dead. Pretty impressive to see one of these things actually work.

• Anonymous
  August 05, 2005
  The use of these kinds of rooms are common practice for contractors working with classified military projects, at least here in Sweden.

• Anonymous
  August 05, 2005
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• Anonymous
  August 05, 2005
  The comment has been removed

• Anonymous
  August 05, 2005
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• Anonymous
  August 06, 2005
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• Anonymous
  August 06, 2005
  You'd really have to put the TV aerial in the Faraday cage as well, or it'll weakly transmit the tell-tale signal. Of course if you put the aerial in the cage, you won't receive anything!
  I've seen great demonstrations of people standing inside Faraday cages that got zapped with tens of kilovolts.

• Anonymous
  August 06, 2005
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• Anonymous
  August 06, 2005
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• Anonymous
  August 06, 2005
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• Anonymous
  August 07, 2005
  <quote>
  I just read on /.
  </quote>
  
  Never a good way to start...

• Anonymous
  August 23, 2005
  Where I work we us Faraday cages on a daily basis, Ours are capable of 100db isolation from the real world, we use the cages to isolate equipment from equipment operating just outside the room, and allows us to test the product inside. They range in size from 20 by 30 feet down to a 10 by 10 and TV's, radios, and cellphones do not work inside the rooms. we do have specially designed 24 X 24 vents made of a honeycomb of small pipes. They almost look like a window when you look directly through. We use special power filters to supply electricity inside the room and special water fittings to supply water. An almost perfect world inside.

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