cellphones as room bugs

[Thor Lancelot Simon]

On Sat, Dec 02, 2006 at 05:15:02PM -0500, John Ioannidis wrote:
> On Sat, Dec 02, 2006 at 10:21:57AM -0500, Perry E. Metzger wrote:
> > 
> > Quoting:
> > 
> >    The FBI appears to have begun using a novel form of electronic
> >    surveillance in criminal investigations: remotely activating a
> >    mobile phone's microphone and using it to eavesdrop on nearby
> >    conversations.
> 
> Not very novel; ISDN phones, all sorts of digital-PBX phones, and now
> VoIP phones, have this "feature" (in the sense that, since there is no
> physical on-hook switch (except for the phones in Sandia and other
> such places), it's the PBX that controls whether the mike goes on or
> not).

It's been a while since I built ISDN equipment but I do not think this
is correct: can you show me how, exactly, one uses Q.931 to instruct the
other endpoint to go off-hook?

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