Presumably the infection includes a driver to turn the audio system into an acoustic coupler, which would appear as a network device on the target machine. At that point any packet sniffer should be able to attach to it.

I'm guessing of course, there's not much real details to go on, and that would mean this infection is more then just a malicious BIOS.

EDIT: Or he's full of shit. Honestly I said that several times reading it, the story was clearly written for sensationalism and made many seemingly impossible claims. I'm no where near an expert but it still set off the bullshit meter too many times.