Filter to Prevent Eavesdropping through Control Wiring 1

[DRWeig]

Request from client today:

"Do you know of a filter that can be installed on control cable to eliminate noise, not electrical noise but eavesdropping? Apparently there is a new government spec out there that certain conference rooms have to have eavesdropping filters installed on all wiring entering the room. Wireless is out of the question because of the way the rooms are constructed and the relationship to where equipment can be installed."

He's referring to typical HVAC control cable. Generally these are headed for thermistors, RTDs, 4-20 mA devices, 0-10V devices, and others. They may also be RS-485 or Ethernet lines. Others may be from 24 VDC or 24 VAC power supplies, to power controllers in the room. I have asked for clarification from the client as to whether this new spec refers to:

The use of the control wires to connect a microphone inside the room to a listening device outside the room;
The use of the control wires to power a wireless-listening or fixed-recording device inside the room;
Sensing actual acoustic vibration transmitted down the conductors or cable jacket from inside the room; or,
Listening to what goes on in the room through the other end of the conduit, or through the hole around the wall penetration.

Until I get answers (which I'll post here promptly), has anyone already run into this spec and found a way to meet it?

Many thanks.


Best to you,

Goober Dave

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[IRstuff]

Depends on what they actually mean. And there is prevention and detection. Prevention would include shielding, RF filtering, armor, and encryption. Detection includes TDR, bug sweeps, monitoring, etc.

http://www.protectivecountermeasure...lity-assessment/residential-eavesdropping.htm

AES256 encryption would be a reasonable minimum for encryption.

TTFN
faq731-376

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[cranky108]

Just a thought, but if you are using DC for control wiring, a simple capacitor works to short AC signels.

 

[MiketheEngineer]

Call James Bond

 

[DRWeig]

We might have to enlist Mr. Bond, or Q, or whoever built The Cone of Silence for Maxwell Smart.

A guy two layers up the technical chain has answered my clarification request with, "We think it's number 3, but number 4 may also be included."

So according to this guy, it's nothing to do with electricity. Vibrating wires and/or sounds coming thru a conduit or other wall penetration.

This is difficult. If spies can bounce some light off of a double-pane bulletproof glass window and record the sounds in the room via the acoustically induced vibration from across the street, how can we stop 'em from putting a stethoscope on a piece of wire?

By the way, the official spec calls the room: The Secure Dome of Silence

It's a serious problem for my client, though. How do you stop vibration from making it down a wire or pipe?

Best to you,

Goober Dave

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[ScottyUK]

Rubber-insulated cable with fine stranded conductors will (probably) not propagate vibration very far. Clamp it in a gland just outside the room boundary to further suppress vibration.

Run your cables in sand-filled ducts?

 

[IRstuff]

seriously? we're talking about tin cans and string?

the answer is "noise generator" which are used in SCIFs built to TLA standards.

http://www.ebay.com/itm/Counter-Sur...te-Noise-Generator-Audio-Jammer-/270817334667

http://www.microvideox.com/noise-generator.html

TTFN
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[DRWeig]

At least I'm getting stuff from y'all to discuss with these folks.

My partner suggested hanging a heavy weight from the cable a few different places inside the room. I heard Scotty's clamp-it-down suggestion from another guy here. Fine strands is a new one on me, I can see how that would help.

One other suggestion was a terminal block screwed down tight to a piece of the structure.

I would be digging right now for the guy whe wrote the spec if I were the contractor. Unfortunately, he's probably a dozen requests-for-info removed from us, and he's probably simply specifying an end result with no idea what is on the market to accomplish it. Dang.



Best to you,

Goober Dave

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[77JQX]

Can't they just turn the radio up really loud and whisper to each other?

 

[itsmoked]

When you install explosion proof EXP stuff you have to seal all the conduits to prevent gas from moving in the conduits. We always used this stuff that came in little metal cans. You popped the lid off poured in a specific amount of water. Stirred it and then spooned it into the conduit of interest. It would turn into a gray solid plug around the wires.

This would certainly block all sound what-so-ever from coming down the conduit, since sound is conducted via moving air. It also would block vibration of the wire itself by forcing the feeble vibrations that would come down the wire into wiggling the entire conduit and the structure its affixed to.

Example:

http://www.platt.com/CutSheets/Appleton/Vertical Conduit13.pdf

Keith Cress
kcress -

http://www.flaminsystems.com

 

[MiketheEngineer]

How about going to the local park, turn up the stereo and have nice outdoor meeting??

 

[msquared48]

Just don't talk under any eaves. Any other problems that need solving?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[IRstuff]

The noisemakers are positive measures that can be readily verified. Other measures may get compromised during maintenance or repairs. Like I said, noisemakers are used in lots of classified facilities.

TTFN
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[IRstuff]

If they're worried about the wiring, then they need to be worried about what's above the ceiling tiles as well. Oh, and the walls need to be thick and damped; there might be some possibility that sympathetic vibrations make their way through the walls, much like how laser Doppler eavesdropping systems can eavesdrop on window panes.

TTFN
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[VEBill]

...there is a new government spec...

Start by requesting the specification number; then ask for a copy of it. If you're not permitted to see it, then ask what you need to do to become authorized. Ask if there's a related handbook that accompanies the spec.

There's likely to be official certification testing and officially certified products (if not now, eventually).

You'll know that you're there when it costs $100k and takes a year to replace the thermostat when it happens to fail.

 

[IRstuff]

There ought not be anything particularly new. The current government information assurance standard is CNSSI-1253, which mandates the implementation of NIST Special Publication 800-53, which mentions eavesdropping one time only, in section PE-4 ACCESS CONTROL FOR TRANSMISSION MEDIUM:

Supplemental Guidance: Physical security safeguards applied to information system distribution and transmission lines help prevent accidental damage, disruption, and physical tampering. In addition, physical safeguards may be necessary to help prevent eavesdropping or in transit modification of unencrypted transmissions. Security safeguards to control physical access to system distribution and transmission lines include, for example: (i) locked wiring closets; (ii) disconnected or locked spare jacks; and/or (iii) protection of cabling by conduit or cable trays. Related controls: MP-2, MP-4, PE-2, PE-3, PE-5, SC-7, SC-8, SC-9.

Note that the cabling in question is transmission cabling, i.e., transmitting data over those cables. Note, also, the specific concern is unencrypted transmissions.

TTFN
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[DRWeig]

All good points as before.

I have submitted a request for the spec. If it's not classified, I'll share it.

Best to you,

Goober Dave

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[jraef]

Wow, this is something way outside of my experiences, I am now flabbergasted to learn that people can listen in on conversations by monitoring vibrations in window glass. Lucky for me, I am never talking about anything that anyone else would be interested in hearing. Just ask my wife...


"Will work for salami"

 

[jraef]

Hit the Submit button too soon. Premature Postilation?

The goop that Keith showed is for explosion proof fittings, might be a bit overkill but the concept is right. The simpler and easier stuff is just called Duct Seal (Google it). It's a non-hardening clay-like putty designed for filling spaces and when used on wires, will not attack the insulation. There is also Fire Stopping material that is used to seal open spaces around wires and in conduits to prevent fire from propagating along the wire insulation, which may be necessary anyway.


"Will work for salami"

 

[MacGyverS2000]

I find it amusing one would try to put controls of any sort into a room that is desired to be "snoop proof"... if you have any doubts, just look at the compromised temperature controls in the corporate apartments used for the government.

Dan - Owner

http://www.Hi-TecDesigns.com