Security researchers in the States say they have developed a cunning new method of "fingerprinting" voice calls that could offer a route to trustworthy caller ID and a barrier against so-called "vishing" or voice phishing.
The tool is called PinDr0p, and works by analysing the various characteristic noise artifacts left in audio by the different types of voice network - cellular, VoIP etc. For instance, packet loss leaves tiny gaps in audio signals, too brief for the human ear to detect, but quite perceptible to the PinDr0p algorithms. Vishers and others wishing to avoid giving away the origin of a call will often route a call through multiple different network types.

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