How Intelligence Agencies can identify the location of anonymous whistleblowers in video interviews using ambient electrical interference captured in audio.

Mann zieht seinen Hut tief ins Gesicht

(Source: Imago)
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by Peter Welchering
In controversial cases, journalists have their anonymous informants front of the camera report on the scandal. This is no longer possible without jeopardizing the whistleblower. Intelligence and security agencies use the humming sound of the mains frequency, to come to the source of the journalists on the trail.
The standard of protection measures include in investigative journalism coverings and disguises. In addition, the voice of the informants is before the broadcast distorted, so that it is not recognized in this way. But these protective measures are no longer effective. Journalists who want to protect their informants still comprehensively may allow such scenes before the camera only adjust by actors.
Network fingerprint as a starting point
Because with an IT forensic method, the interference of electrical power frequency can be filtered out in sound recordings and compressed into a kind of network fingerprint. This network fingerprint is then compared with frequency databases to find out when and where the picture was shot.