[VOIPSEC] Soft Phone Vulnerabilities

[Matthew Kaufman]

I can't recommend a document, but as an author of a softphone for
Windows and Mac, I can tell you that turning the microphone on when
you're not expecting that would be trivial for an unscrupulous
programmer. Getting the data out undetectably is harder... but you 
should consider the risk that the data might be saved and played 
out over the network after the fact, perhaps at a lower rate to
reduce the risk of detection, or only during valid calls, to mask
the utilization among real traffic.

This same risk applies to hardware digital phones as well... if this
danger is part of your threat profile then the only way to be sure is
to have a switch that ensures that both the speakerphone and handset
microphones -- or all the microphones attached to your PC -- are
physically disconnected or muted (short circuit) when the phone is "on
hook", and verify that the circuity is actually present and functioning
in your particular case. Or use open-source software that you can
and do inspect for risks, and then compile yourself using a known safe
compiler.

This is simply the extension of the rule about firewalls: the only safe
one is a pair of scissors.


Matthew Kaufman
matthew at matthew.at
http://www.amicima.com