Comment Simple defence (Score 1) 121
A simple defence would be to have ultrasonic noise generators emitting enough interference to effectively jam any transmissions. It should be no more audible than the transmissions.
Of course, the average user wouldn't need or probably want this (unless they're security paranoid/enthusiasts), but it might be useful in environments where information security is essential. Maybe even 'hardened' secure devices could have built in noise generators that can't be software disabled as an extra defence feature.
It might seem simpler to just limit the frequency ranges of the built in speakers/microphones, but it doesn't eliminate the threat completely as it is still possible there could be a headset, USB sound interface or devices in the microphone and earphone jacks in use without these filters. This way, regardless of the kind of sound I/O, the surrounding area of the device is blacked out.
Of course, the average user wouldn't need or probably want this (unless they're security paranoid/enthusiasts), but it might be useful in environments where information security is essential. Maybe even 'hardened' secure devices could have built in noise generators that can't be software disabled as an extra defence feature.
It might seem simpler to just limit the frequency ranges of the built in speakers/microphones, but it doesn't eliminate the threat completely as it is still possible there could be a headset, USB sound interface or devices in the microphone and earphone jacks in use without these filters. This way, regardless of the kind of sound I/O, the surrounding area of the device is blacked out.