nonintrusive signal sniffing

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I'm interested in experimenting with how to non intrusively sniff signals on
a wire.  Examples are phone lines, VGA video, NTSC video, RS232, etc.  One
of the first I'd like to try is NTSC video on a standard RG-59 coax.  Is
there enough radiation from these to detect anything useful if you can get
in close ?  Or does the coaxial cable effect attenuate it so much that its
not feasible ?

Assuming there is enough radiated signal from it to detect something, what
is a good technique for doing it ?  Use a loop of wire near the cable to
detect the field and amplify it ?  Wrap wire around the coax ?

I know the questions sound ominous but its really for a good purpose.  I'm
hoping to apply for a surveillance or electronics related job in a law
enforcement field.  Right now I've a few semesters of electronics classes
behind me and I'm trying to learn some practical things.



Re: nonintrusive signal sniffing

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signals on
 One
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Is
can get
that its
what
to

I bet they won't tell you that on a public forum

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We will never know.

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law
classes


Re: nonintrusive signal sniffing

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signals on
 One

Take a spectrum analyzer. Wave the probe near your signal line of
interest. Report your results.


Re: nonintrusive signal sniffing
I donot remember enough of grad electronics to know whether this is
feasible or not - it is just an idea you could work upon.
You can try two things:
1)You may "touch" the cable to measure provided you use a home-made
probe/scope with its load adjusted such that it makes very less
difference to the source whether the actual termination is connected
or the termination plus the probe.
2)You can measure the complete load ( resistive plus reactive)
presented by your sink circuit to the source - then you can model a
pobe/meter with the same load and connect it thus dispensing of the
actual sink ciruit completely.


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Re: nonintrusive signal sniffing
 >
 > I'm interested in experimenting with how to non intrusively sniff
 > signals on a wire.

k v wrote:

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I don't think dispensing of the actual sink is non-intrusive.  ;-)

Thad


Re: nonintrusive signal sniffing
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On the overall scheme of sniffing what you ask is trivial.  If you want a
challenge try for a non-intrusive sniff of a fiber optic cable.  What you
see on the tv and movies is mostly fiction, but remember truth is much
stranger than fiction.

Check out this Tempest site: http://www.eskimo.com/~joelm/tempest.html .
Around 15 years ago the US govt. greatly scaled back the number of locations
that needed Tempest certified equipment and mostly killed off the market for
producing really quiet equipment.  The need and market still exist.  If you
are interested in pursuing this field check with your professors that
specialize in RF.  They will probably know enough to point you in the right
direction.

--
Scott
Validated Software Corp.



Re: nonintrusive signal sniffing
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Google for 'tempest security' as a starting point.  It's not
specifically directed at wires, but the concept is extensible.

Re: nonintrusive signal sniffing

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   You should at least learn a few of the terms used in the electronic
security field, else you'll have no more influence than a storm in a
teapot.

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   You've never got a bunch of parts at Radio Shack and played around
with them? Know how to make circuit to flash an LED?

   I've got some ideas how to do these things (the things you ask
about, as well as making circuits that flash LED's), which might or
might not be worth anything, but I won't share them with strangers on
the Internet (well, I might share how to make an LED flashing
circuit).

   I recall seeing a movie (I don't recall the name, this was on TV in
the US at least 20 years ago) involving some sort of bank or jewelry
heist. Two guys synchronized their watches. Later, at the very moment
when one got the attention of a security guard whose job was to (among
other things) keep an eye on a "CCTV" [such an old-fashioned term]
monitor connected to a camera elsewhere in the building, the other guy
was in a utility room cutting the video cable and splicing in the
output of a VCR which was playing a recording of the camera from a few
days earlier. The first guy successfully kept the guard's eyes away
from the monitor while it had 'snow' on it, and they pulled it off.
The guard even got a call about a possible problem when the robbery
was going on, and he said "I don't see any problem, things look fine
to me."
   The moral of that movie is: Don't dismiss or ignore the power of
social engineering.

-----
http://mindspring.com/~benbradley

Re: nonintrusive signal sniffing

Quoted text here. Click to load it

   You should at least learn a few of the terms used in the electronic
security field, else you'll have no more influence than a storm in a
teapot.

Quoted text here. Click to load it

   You've never got a bunch of parts at Radio Shack and played around
with them? Know how to make circuit to flash an LED?

   I've got some ideas how to do these things (the things you ask
about, as well as making circuits that flash LED's), which might or
might not be worth anything, but I won't share them with strangers on
the Internet (well, I might share how to make an LED flashing
circuit).

   I recall seeing a movie (I don't recall the name, this was on TV in
the US at least 20 years ago) involving some sort of bank or jewelry
heist. Two guys synchronized their watches. Later, at the very moment
when one got the attention of a security guard whose job was to (among
other things) keep an eye on a "CCTV" [such an old-fashioned term]
monitor connected to a camera elsewhere in the building, the other guy
was in a utility room cutting the video cable and splicing in the
output of a VCR which was playing a recording of the camera from a few
days earlier. The first guy successfully kept the guard's eyes away
from the monitor while it had 'snow' on it, and they pulled it off.
The guard even got a call about a possible problem when the robbery
was going on, and he said "I don't see any problem, things look fine
to me."
   The moral of that movie is: Don't dismiss or ignore the power of
social engineering.

-----
http://mindspring.com/~benbradley

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