kaputnikGo
commented
6 years ago Hi, the active jammer is attempting to flood a given range of frequencies (NUHF) with noise so that it confuses any beacon tracker SDKs from finding the specific signals it is listening for.
For example, on this page http://www.cityfreqs.com.au/pilfer.php the second image from the bottom shows a spectrogram of such an attempt that is making such noise over the Sonarax signal. This page also has examples of other beacon signals. I also added the image below.
The idea behind it is that most of the SDKs look for repeating signals of a particular type. With the active jammer running it can add a lot of noise or false signals so that the SDK fails to recognise the particular signal that is meaningful to it. This technique is dependent on the loudspeaker of the phone being able to drive a loud enough signal that it dominates any tracker signal underneath.
A lot of the beacon tracker SDKs use algorithms that seek the strongest (magnitude) frequency signal within a given time period. If it finds a candidate match then typically the tracker will then examine more audio to see if there is more signals that match the signal pattern it is looking for. If the active jammer is running then ideally the beacon tracker SDK will never find a recognisable signal, just a lot of random noise.
As for its uses, i mainly use it for testing and experimentation (none of my main phones have tracker SDKs in them) but i could imagine a scenario where you wanted to block signals for other nearby devices that dont run the jammer (iphones etc). Or maybe you cant use the passive jammer (VOIP call), or maybe the android API changes in such a way to make the current passive jamming technique unreliable.
At the moment the active jammer emits a lot of audible artifacts (mainly to allow it to be heard) but future versions may have a switch so that it can be run "silently" and not disturb.
Hope this makes sense.
Image below; example of active jammer noise signal over a Sonarax beacon signal.
I do not understand what the "active jammer" frequencies are supposed to be jamming. The passive jammer is easy enough to understand, but can you describe a scenario where outputting random frequencies [19-21]kHz is going to prevent surveillance?