Shielding a room from all RF in and out?

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Red Squirrel

Red Squirrel

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May 24, 2003
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What are some good resources to read up on how to do this? With all the stuff these days that spies on us, including CPUs that have a 3G radio in them, I want to look into the options of completely shielding my server room from all types of RF from low to high frequencies. High frequencies are probably the most important and probably easier to block against but considering the secrecy of spy devices it's best to cover as wide spectrum as possible. There is obviously more to it than just plastering the walls, ceiling and floor with tin foil, and the material you use, the shape of installation etc probably all plays a role. Ex: you can wrap your phone in tin foil and still have it receive a call, so it's more complicated than that.

I'd like to at least read up on various techniques, and then decide what is worth doing if anything. My options are rather open as currently the room is just framed, there is no drywall up. There is a drycore subfloor though, which idealy, I would want some shielding material to go UNDER it and not over, but since it's a basement, I'm almost wondering if I could get away with not shielding the floor as any RF would basically bounce around and be directed down and dissipate. But maybe not.

Also since there are various wire penetrations such as electrical and data, that is obviously going to allow some RF to get through, what are good techniques to deal with this? Is optical barrier the only way? (ex: fibre with a switch that is outside the room).

I can probably rerun a lot of cables so that they all enter in one common location as well.

With all this spy stuff I just feel I need to do more to try to protect myself. At very least protect the most critical equipment. Shielding the entire house would be prohibitive. Maybe if ever I build one then it's something I could do.
 
Red Squirrel

Red Squirrel

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Mr Evil said:
However, if you're trying to protect computers, then a bigger concern would surely be the gaping security hole that is proprietary hardware with a network connection.
Click to expand...

Yep that's a big issue right there that I need to figure out how to protect against too. These CPUs use a 3G radio too, so lbocking that is half the battle, need to figure out how to block the network part too. Technically you could just be very diligent with what outgoing ports your firewall allows, but if your firewall has an intel processor then all of that is moot as it will bypass the firewall.

Almost need to use a microcontroller or something rather low level and custom to act as the firewall. I wonder what kind of packet switching performance you could get with something like an Atmega168 or something. You'd have to write the ethernet/ip stack though. :eek:

As a side note on subject of Faraday cages, does it have to be a cage to be effective? Or can it just be a continuous shield? Maybe that's why my test of wrapping a phone like a hot potato does not actually work, the holes actually play a role in blocking the waves and a continuous shield just acts as an antenna?

One way to protect from electrical related interfeerence signals (current changes and such) would probably be to use a dual conversion UPS system, perhaps even with something that introduces it's own noise. SMPSes may be enough on their own.
 
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C

C1

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Feb 21, 2008
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Isnt another possibility to just implement an RF jammer in the frequency range of interest. These are commercially available in non-US countries, but there are all kinds of schematics and even kits available on line.

You may also want to think about how to use encryption. Seems just the other day I read that the now use of multi-encryption schemes is an NSA headache.

=========================================================
House Homeland Security panel first heard more pleading from FBI Director James Comey to take action -- the action he desires, mandating backdoors, etc. -- to do something about their encryption dilemma. Comey told the room that encrypted comms are increasingly hindering investigations by law enforcement. He told the panel, "The needles we're looking for are becoming invisible to us in case after case after case."
 
Red Squirrel

Red Squirrel

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C1 said:
Isnt another possibility to just implement an RF jammer in the frequency range of interest. These are commercially available in non-US countries, but there are all kinds of schematics and even kits available on line.

You may also want to think about how to use encryption. Seems just the other day I read that the now use of multi-encryption schemes is an NSA headache.

=========================================================
House Homeland Security panel first heard more pleading from FBI Director James Comey to take action -- the action he desires, mandating backdoors, etc. -- to do something about their encryption dilemma. Comey told the room that encrypted comms are increasingly hindering investigations by law enforcement. He told the panel, "The needles we're looking for are becoming invisible to us in case after case after case."
Click to expand...

I was thinking about this, as it would break protocols that require any kind of acknowledgement, but technically these spy devices only need to send data to work, so a jammer would be useless unless you jam all the way to the destination (tower) and that is obviously a bad idea. Idealy I just want to blanket block all forms of RF in one go, if it can be somewhat easily be done at a resonable cost.

It's nice to know that encryption is at least semi effective, if it makes their lives harder then good. They can still eventually break it though, ex: that iphone incident where they really wanted to get into someone's phone.
 
Red Squirrel

Red Squirrel

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Hmmm they do say a full solid plate room is a good shield, wonder why my experiments did not work. Maybe there was a small hole somewhere in the foil, they do say a tiny hole is enough. Hole has to be big enough to let that wave length through as well which is not that big. Ex: holes in microwave oven door are fairly tiny, a bit bigger and waves will get out.
 
A

A5

Diamond Member
Jun 9, 2000
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1) Even if your CPU has the hardware for a 3G "radio" in it, there is no external antenna hooked up to it that would allow it to transmit with any real kind of power.

1a) I suspect your references to this are actually about this paper: https://www.usenix.org/system/files/conference/usenixsecurity15/sec15-paper-guri-update.pdf
Which does not state anything like that, and is actually based on malware being used to modulate the memory bus to achieve very short range transmissions (up to 30m at 1 kbps with dedicated hardware). It also contains a useful summary of available work in the area.

2) If you actually want to do this, this page seems to have decent information: http://www.metexcorp.com/emirfi_theory.cfm

3) Wrapping your cell phone in tin foil probably didn't work because cell phones are really sensitive antennas and tin foil isn't actually super effective at blocking RF. A properly designed (and grounded) wire mesh is what you need.

4) If you are really, really serious about this, I would recommend learning some 3D calculus and college-level electromagnetics. There are equations for all this stuff, and I think educating yourself would also ease your mind a bit about how hard this all is.

5) Your government doesn't care enough about you to spy on what you're doing unless you're already on their radar for other reasons.
 
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M

Mark R

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Oct 9, 1999
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RF shielding is difficult, but it really depends on how much attenuation you need.

I've seen a lot of MRI rooms which are very sensitive to external RF, to the point that if a filament in a lamp inside the MRI room starts to degrade, the RF from the failing filament will leave the MRI machine non-functional.

These rooms are typically built from copper panels in the region of 1-2 mm thick soldered together, over the existing walls/floor/ceiling (usually a wood frame), or sometimes copper foil over aluminium panels. Transparent windows into the room are built like a microwave oven door, with an internal mesh. Doors are metal plated, and metal edges, with overlapping spring finger contacts on the door edge and frame, so that when the door is closed a seamless connection is made across all the door edges.

Cable penetrations into the room are either through RF noise filters, or through waveguide tubes (RF cannot pass through a conductive pipe with a diameter much less than a wavelength, if the pipe length is much longer than a wavelength). These waveguide tubes provide an easy method to run fiber cables into the room. Interestingly a lot of new monitoring equipment for MRI now uses 2.4 GHz wireless transmission - at this frequency, the RF can penetrate the holes in the cage and waveguides, so it is possible to transmit from inside the room to outside, provided that the transmitter is extremely heavily filtered to ensure no spurious RF production in the scanner frequency range.

Example construction pics:
http://www.mritechnologies.com/shielding-upgrades.html
 
D

Dude111

Golden Member
Jan 19, 2010
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I would think lining the room with tinfoil might be effective as tinfoil will block most signals I believe..........
 
MongGrel

MongGrel

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Dec 3, 2013
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Red Squirrel said:
As a side note on subject of Faraday cages, does it have to be a cage to be effective? Or can it just be a continuous shield? Maybe that's why my test of wrapping a phone like a hot potato does not actually work, the holes actually play a role in blocking the waves and a continuous shield just acts as an antenna?
Click to expand...

Some form of Faraday cage came to mind myself, it could be continuous, but wouldn't be cheap I imagine.

Would take a lot of carbon fiber mesh on the walls and ceiling at any rate I would imagine.
 
mindless1

mindless1

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Aug 11, 2001
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Not to be difficult or anything, but that would be one point of data vs others who claim it does block their phone.

Foil should block a phone, are you not wrapping it completely or something?
 
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Red Squirrel

Red Squirrel

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I did another experiment, it seems you have to wrap it with two layers and ground it. One layer and a call could go through, but two layers, and grounded, it did not go through. I was testing with a streaming YT video but that turned out to be a bad test since it buffers way ahead. I wanted to do a ping test but was hard to get camera shot of phone and computer at same time. But video probably not necessary at this point as it did in fact block it, it just took more effort than I originally figured. Not sure what this means in terms of a room though, like it seems one tiny little hole or badly tucked seam and it could render the entire shield useless. If using (real) duct tape to join multiple sheets of foil I imagine the glue that separates the tape from the foil would be enough to let RF through as well. Need to keep stuff like 40Ghz in mind too, as I'd imagine certain spy tech would use rather exotic wave lengths to not be easily detectable by consumer gear. That's something I would not really have an easy way to test though.

I may have to start small and experiment with a small box/enclosure and see if I can get a shield system going. Then I can experiment with the waveguides for bringing in data/electrical inside the box. Idealy I want it to block as many bands as possible, if all, so I'll have to test with FM radio and other stuff too.

I do want to build a small grow box, and I actually wanted to use some kind of foil to reflect light around, so maybe I can double that as an experiment before I use it to grow stuff.
 
Red Squirrel

Red Squirrel

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MaxDepth said:
Faraday Cage
Click to expand...

Obviously. But I'm looking for more technical info on how to go about doing that. It seems tin foil may very well work, but I'll probably want something thicker that comes in a bigger package, maybe that stuff they use in attics. The tricky part will be figuring what to do for seams and penetrations as from what I saw in my experiment you really have to wrap it good for it to work. Though from some of what was posted it seems I could probably use some kind of wave guide, basically metal conduit that does a couple zig zags. Will require more experimentation on smaller scale.

This is more of a long term project if I even do it at all, so just throwing ideas around at this point.
 
mindless1

mindless1

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Foil lined insulative sheeting then cover cracks with HVAC aluminum duct tape, which is at least 2-3 times thicker than your average cooking foil, but such tape also comes in different thicknesses with increasing price.

If you find you need thicker metal than the lining on insulation panels you can get foil and sheet metal in greater thickness, but of course the cost is roughly proportional to that, or much higher for some specialty product but standard sheet metal is not a specialty product.

This still leaves room ventilation but you should be able to use a typical overlapping mesh metal filter panel.
 
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MaxDepth

MaxDepth

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Jun 12, 2001
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Foil sheets for small applications like the size of a garbage can. You'll run into too much expense and maintenance issues for something the size of a room. What you'll need is small gauge screens that will work just as effectively as foil. You'll have to make it a full enclosure meaning floor and ceiling too, like a cube. So you are ignoring for the most part, outlets and pipes, because your cage, unless built into your walls, will be a room inside your room.

Link for illustrative purpose (not really paying attention to the people talking in it):
https://www.youtube.com/watch?v=P4UdozjyLlA

And since MIR rooms are essentially Faraday Cages too. Here is a company that makes them for businesses: http://www.sirp-france.com/cage-de-faraday.html?sSort=name
 
Red Squirrel

Red Squirrel

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I'm not sold on grid idea, that tends to be tuned for very specific frequencies, I'm looking more for something that covers all. For example the grid on a microwave door is good for 2.4Ghz or so, but that's it.

Floor may be an issue though, something I was not taking into account, was figuring a "dome" might be enough, but it probably won't be. The soil/ground is probably not a very good shield.
 
William Gaatjes

William Gaatjes

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May 11, 2008
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Occasionally, at work we have to do some emc/ emi qualification testing at a company called Dare.
http://www.dare.eu/

These people have true cage of Faraday cage rooms for measurement purposes and nothing can get in or out, but everything is specially crafted. Even cables need special entry points to prevent RF noise leaking away or getting in.

For emc/emi purposes there are two ways of emission, conducted and radiated. Conducted is for example through cables and radiated is as the word says radiated through the air.
 
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