I was reading this article from Ars on badBIOS and came across this line which states
the malware, has the ability to use high-frequency transmissions passed between computer speakers and microphones to bridge airgaps.
and wondered if this attack vector was possible ? Not only me , but all other readers were wondering if this had any logical explanation.Can a computer transmit packets via high-frequency sounds broadcast over speakers ?
Can a computer transmit packets via high-frequency sounds broadcast over speakers ?
In theory yes, it's the same as transmitting over analogue phone lines. Packets of data could be encoded as pulses and tones to be broadcast over speakers. As most speakers can generate high frequency noises which are beyond the range humans can hear, I see no reason why this couldn't happen.
and wondered if this attack vector was possible ?
The concept of receiving the packets is slightly more complex in that it couldn't be the initial vector. As indicated in the article, the initial infection was likely due to an infected firmware in a USB storage device.
I would theorize that the virus isn't transmitted via sounds initially, but is using audio as a method of command & control in environments where networking is either not available or severely restricted due to security measures.
As a sole means of attack vector it is BOGUS. In order for the victim to receive the attack it must be listening to the audio broadcast of the other machine first. And it must be able to decode that broadcast.
That implies that the victim computer is ALREADY infected by something which installed the listening software.
As a means of communication between 2 infected computers it is by all means plausible.
It is not even new.
What do you think those old acoustic modems where doing back in the 80's ? Or fax-machines ? Communicate by sound !
Can a computer transmit packets via high-frequency sounds broadcast over speakers ?
Sure. If a mic can pick up the sound and a speaker transmit the sound, it's possible. There's many, many methods of transmitting data via sound. Fast methods are complicated and require optimum conditions, but very slow methods such as PSK used in 300 baud modems are more robust.
Most PC's can create sounds 20-20KHz and beyond. I don't know the maximum frequency of the standard PC speaker but it can go pretty high. Most people can't hear very well above 15KHz ... but I'd be surprised if your average PC mic picks up frequencies outside the normal vocal range (4KHz) very well.
Of course, no OS has this capability built in. There is no program in any standard OS that accepts data over modulated high-frequency sounds received by speakers ... except possibly things like Dolby/DTS decoders for audio. Maybe, just maybe there's an exploit there waiting to happen.
So while malware (or any other program) could communicate with another system using this technique, it's really unlikely that it could spread using this technique. I don't think consumer grade laptop mics are capable of it anyway.
Of course its technically possible. In order for a computer to communicate, it simply needs to transmit 1s and 0s, which can be done via sound. As for high frequency sounds, I know my iPhone can make a sound that annoys my cats, but I cant hear it, I assume my PC speakers are just as capable.
