Xref: utzoo misc.consumers:14002 misc.misc:8360 sci.misc:3836 sci.electronics:8256
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!uakari.primate.wisc.edu!xanth!ames!dftsrv!hq!illgen
From: illgen@hq.af.mil (Keneth..Illgen)
Newsgroups: misc.consumers,misc.misc,sci.misc,sci.electronics
Subject: Re: Telephone privacy gadgets
Keywords: Telephone, wiretap, bug, countermeasures, etc.
Message-ID: <397@hq.af.mil>
Date: 17 Oct 89 18:26:45 GMT
References: <799@mccall.uucp> <776@ariel.unm.edu>
Reply-To: illgen@hq.UUCP (Kenneth..Illgen)
Followup-To: misc.consumers
Organization: Air Force HQ, The Pentagon
Lines: 73

In article <776@ariel.unm.edu> ee5391aa@hydra.unm.edu.UUCP (Duke McMullan n5gax) writes:
>In article <799@mccall.uucp> tp@mccall.uucp (Terry Poot) writes:
>>There are gadgets one can put on a telephone that purport to tell you if
>>the conversation is being recorded. Does anyone know if they work?
>
>The answer is an absolutely definite maybe, with an appended probably not.
>
>First, "being recorded": There are ways -- of varying reliability -- to tell
>if your line has been tapped, but it'll require something on the order of
>deitic omniscience to tell you what's being done with that signal. Still, it's
>very likely that if you're tapped, you're being recorded.
>
>Prevention (as usual) is the best, but what you asked about is detection. You
>can buy from various sources instruments purported to tell you if your line has
>an unauthorized tap on it. Do they work?
>
>Usually not.
>
>The methods vary. You can measure line impedance, which will detect low budget/
>unsophisticated taps, you can listen for noise on the line, which is useless,
>or you can use TDM.
    
     You mean TDR. TDM is Time Division Multiplexing and can't help you 
detect a phone tap.

>That's technicalese for Time Domain Reflectometry. The idea is that you send a
>sharp pulse signal down the line, and watch carefully (i.e., with an expensive
>instrument) for reflections of the pulse which occur at every sufficiently
>abrupt impedance change in the line (i.e., at a tap). The TDM system also
>detects other telephones, connections to the service block, extension line
>connections, staples which penetrate the insulation, sharp kinks in the wire,
>etc. The TDM "signature" of the line is a pretty complex signal. This means
>that you must have the signature of a "clean" line, and compare this with your
>signatures as time goes on. When you spot a change, look into it.
>
>Is that reliable? Well...sort of. 

     Actually it is very reliable provided you know the layout of the location you want tested. Testing in your home with a TDR would be a waste of time.
It would take you less time to walk through the house to the junction box
the it would to call Rent-A-Center to get a TDR.
But if you know how the wires run in your office it can provide a clear indication of additional devices being attached to a line.

>For an authorized tap (done by the TelCo), forget detection. It's done at the
>central office (entirely in software, I'm told) and there exists no reasonable
>detection method from your end of the line.

     This is true except that it's not entirely done by software. The software 
keys the line to be tested but the instrument that does the recording is put 
'on-line' which will add to the impedance load. This (if you happened to be a
a phone company technician in the building could be detected) used to be the
little click you would hear. The click still happens only now it's a lot 
softer.

>We should note that TDM methods usually involve breaking the line connection
>at the service entrance and terminating the block with the line's
>characteristic impedance, so you're not connected to TelCo when you do that
>test.

     If you had the money and the paranoia you could simply tie in your TDR
and your phone into a diplex plug and eliminate the first reflection on your
scope by zeroing your meter after the pulse caused by your telephone/TDR.
You don't have to disrupt the line to measure. This point could probably be
debated regarding using and pulsing at the same time but my personal feeling
is that the frequencies wouldn't interfere or bring down any equipment.

>This applies to most detection methods: A simple bug is fairly easy to detect;
>a sophisticated one very difficult. The measures have a way of staying a step
>or two ahead of the countermeasures.
>Additionally, there's the cost factor. As expensive as GOOD bugging equipment
>is, the corresponding ECM stuff is a lot more expensive.

     Generally speaking cost can be pretty high however a reliable undetectable
bug can be planted for around $100.00. It all comes down to where you plant it.