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Filter to Prevent Eavesdropping through Control Wiring

Filter to Prevent Eavesdropping through Control Wiring

Filter to Prevent Eavesdropping through Control Wiring

(OP)
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

Haven't see the forum policies? Do so now: Forum Policies

RE: Filter to Prevent Eavesdropping through Control Wiring

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.protectivecountermeasures.com/security-...

AES256 encryption would be a reasonable minimum for encryption.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Filter to Prevent Eavesdropping through Control Wiring

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

RE: Filter to Prevent Eavesdropping through Control Wiring

Call James Bond

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
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

Haven't see the forum policies? Do so now: Forum Policies

RE: Filter to Prevent Eavesdropping through Control Wiring

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?

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
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

Haven't see the forum policies? Do so now: Forum Policies

RE: Filter to Prevent Eavesdropping through Control Wiring

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

RE: Filter to Prevent Eavesdropping through Control Wiring

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%2...

Keith Cress
kcress - http://www.flaminsystems.com

RE: Filter to Prevent Eavesdropping through Control Wiring

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

RE: Filter to Prevent Eavesdropping through Control Wiring

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

Mike McCann
MMC Engineering
http://mmcengineering.tripod.com

RE: Filter to Prevent Eavesdropping through Control Wiring

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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Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Filter to Prevent Eavesdropping through Control Wiring

Quote (OP)

...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. smile

RE: Filter to Prevent Eavesdropping through Control Wiring

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
FAQ731-376: Eng-Tips.com Forum Policies

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
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

Haven't see the forum policies? Do so now: Forum Policies

RE: Filter to Prevent Eavesdropping through Control Wiring

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"

RE: Filter to Prevent Eavesdropping through Control Wiring

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"

RE: Filter to Prevent Eavesdropping through Control Wiring

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

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
Yeeesh! Spies aren't fun, sexy, suave, daring, and exotic when you're building things for them.

Thanks for the conduit seal / duct seal / firestop suggestions, those might work too. Our client might combine most of the ideas above and make a submittal. The submittal rejecter (if rejected) will have to at least give us hints. I think we have some conduit seals and firestop in stock, will have to check with the product managers.

Still no word on if or when we'll see the spec. I don't even know which agency this thing is for, or in which hemisphere it's located. All I know is "Federal Government." They're probably reading this as I type and having a good laugh.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

RE: Filter to Prevent Eavesdropping through Control Wiring

Quote (IRstuff)

"...noisemakers are used in lots of classified facilities."

We usually call them "attendees".

There's a non-hardening goop sold in tubes that (in Canada) we often call "Acoustical Sealant". The intended purpose is to smear on studs before mounting the drywall so as to reduce sound transmission. It's also very commonly used to seal-up 6-mil ultra poly+ sheets to achieve a permanent air-tight vapour barrier. This sort of product could be useful.

If one was paranoid, one might wish to open up the cables and dampen the individual wires.

There's a concept of 'inspectable area'. If the adjacent rooms are under control (inspected and locked), then one shouldn't need to deal with the risk that an enemy agency sets up a rack of monitoring equipment in the next room.

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
Thanks VE1BLL.

That's another one to add to the list. Our client is submitting tomorrow, a combination of all the good suggestions here and some others they got from somewhere else. The good news is that none of the other subcontractors know what to do either. There's supposed to be some government lady coming to give them the requirements verbally.

Best to you,

Goober Dave

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RE: Filter to Prevent Eavesdropping through Control Wiring

"...give them the requirements verbally."

That's sort-of ironic.

RE: Filter to Prevent Eavesdropping through Control Wiring

I thought using fiber optic cable would prevent anyone from listening in by inductive methods on cables. As far as a safe room like that is not using some kind of lead paint or screen on walls stop people from electronic listening thru walls?

RE: Filter to Prevent Eavesdropping through Control Wiring

Fiber is not secure, given physical access to a modest segment anywhere along its length.
Remove or slit the jacket, bend the core a little, and detect the light that leaks out.

Mike Halloran
Pembroke Pines, FL, USA

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
Remember, controlsdude -- this isn't about sensing electrical (or optical) signals, it's about stopping the transmission of vibration along a physical path from inside the room to outside. You're right about the walls themselves. I don't know how they prevent listening-thru with the technology available today, but I'm betting they've done it.

That's interesting, Mike. Now you've got me wanting to experiment.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

RE: Filter to Prevent Eavesdropping through Control Wiring

Throw an electronic solution at the problem. Don't let the wire directly connect. Run the first wire to a hub inside the wall, which will then retransmit on a different wire.

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
Thanks TomDOT, another version.

I hope I'll get to find out what the gummint wants...

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

RE: Filter to Prevent Eavesdropping through Control Wiring

This is an interesting thread. The problem with afterthought bandaids to isolate a room to a high standard of security when the room was not designed that way in the first place is that you are not likely to patch all the holes. It depends on how valuable the confidential data is and how serious the spy is.

RE: Filter to Prevent Eavesdropping through Control Wiring

I can't help but think of the plastic room from the X-men movie :)

How about no physical contact at all between the room and its surrounding structure? Make the secure room itself a self-contained self-supporting box, floating on magnets like a maglev train. The entrance door has an airlock that retracts in the surrounding room. The surrounding room is climate controlled so you need less fans in the isolated room. Or go the opposite route, and give the secure room self-contained atmosphere and evacuate the surrounding room. In space, no on can hear you share state secrets. Power (for lights, coffee maker, etc.) can be transmitted through inductive coils under the floor, picked up by secondary coils in the floor, like a flat air-gap transformer. Self-contained power is also an option; run the lights off batteries. If you need to send out/in any data signals, convert them to optical (laser LED) signals in one side of the wall, shining on receptors on the other side of the wall panel. Narrow beams with covers around them so that no one else can see the light except the intended target.
This is very sci-fi. Inefficient but you've got a government budget to spend.

STF

RE: Filter to Prevent Eavesdropping through Control Wiring

You also have to secure the maglev circuits.

Mike Halloran
Pembroke Pines, FL, USA

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
Just an update -- they're not talking.

Our client is stuck with running a twisted pair through the wall, different room construction is not on the table.

It would be interesting to make a soundproof room from scratch, though. Perhaps something super-heavy like a bank vault, surrounded by a larger concrete room, with IRstuff's noise generators in the interstice. Maybe the vault could have its own foundation, floating on water or an air cushion.

Add armed guards around the perimeter, and you're done. Stick a fork in it.

Note that I said soundproof -- not spyproof. If the bad guy is sitting at the conference table with you, you're toast.

You could also do it like the North Koreans are supposed to have done it. 30 stories underground, with soldiers everywhere above.

I'll keep trying to pry the info out of our client. They haven't said the word "classified" yet.

Best to you,

Goober Dave

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RE: Filter to Prevent Eavesdropping through Control Wiring

Dave, they haven't said "classified" because it is sooo seekrit that the fact it even is a seekrit is classified. So you would have to be cleared in order to be told that you can't be told.

:D

RE: Filter to Prevent Eavesdropping through Control Wiring

Quote (DRWeig)

they're not talking
Problem solved, eavesdroppers have nothing to hear.

RE: Filter to Prevent Eavesdropping through Control Wiring

Just use the cone of silance, and forget about the other stuff.

RE: Filter to Prevent Eavesdropping through Control Wiring

If it's just a twisted pair that they're worried about, then any of the original suggestions would work, i.e.; provide lots of slack and hang a weight on the cable. So long as the cable is not taut, the damping from the insulation should significantly attenuate any acoustic vibrations impressed on the cable. It's already at an absurdly low level to begin with, given the low capture cross-section for collecting the vibrations in the first place.

TTFN
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Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Filter to Prevent Eavesdropping through Control Wiring

(OP)
Agree, IRstuff.

Best to you,

Goober Dave

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