In a post that reads like science-fiction, a security researcher claims that malicious code was being passed between computers. A few quotes:
... "badBIOS," as Ruiu dubbed the malware, has the ability to use high-frequency transmissions passed between computer speakers and microphones to bridge airgaps.
... It's also possible to use high-frequency sounds broadcast over speakers to send network packets. Early networking standards used the technique, said security expert Rob Graham. Ultrasonic-based networking is also the subject of a great deal of research, including this project by scientists at MIT.
... Then, when Ruiu removed the internal speaker and microphone connected to the airgapped machine, the packets suddenly stopped. With the speakers and mic intact, Ruiu said, the isolated computer seemed to be using the high-frequency connection to maintain the integrity of the badBIOS infection as he worked to dismantle software components the malware relied on.
This has me highly skeptical. As an attack-vector, is it in any way possible to exploit an uninfected computer via only an active microphone? Assuming such trickery is even possible, why didn't the researcher simply record the audio with an (analog) recorder to validate the claims?