An attacker with enough skill can make a computer leak information in ways the average user wouldn't even think of. We've previously covered cases like a phone's radio, fans, and even the sound of a hard drive. But now it's the turn of headphones. With a simple modification to Realtek audio drivers, any pair of connected headphones can be turned into a microphone with capabilities similar to a dedicated passive model.
Ben-Gurion University has shown a special interest in computer security and privacy, to the point that its experts have developed different exfiltration systems that seem too complex or impractical from a general point of view. Still, these works remind us of a simple truth: consumer devices were not designed with security as a priority. Even the noise of a fan can transmit information as long as there's an appropriate receiver on the other side, but leaking data is just one of many possible tasks. In fact, a computer could be listening to everything we say even if there's no microphone connected...
The SPEAKE(a)R technique
The official name for this technique is 'SPEAKE(a)R', and in essence it converts headphones into microphones. The reassignment of connectors is quite common in integrated sound cards, and depending on the manufacturer, the user can modify roles at will. Realtek drivers and chips fall into that category. So with a small hack on the driver, the Ben-Gurion researchers transform a pair of headphones into a standard microphone that captures voices with audio quality similar to a passive microphone, more than enough to listen to a private conversation.
Why it matters
That headphones work as a microphone is nothing new. The real problem is divided into two parts: the drivers are insecure, and the presence of Realtek chips in the market is impressive. Realtek hasn't made any comment after the publication of 'SPEAKE(a)R', and personally I don't think they will. There might be a possibility to 'cauterize' the function at the driver level, but these can be replaced with previous versions, and also other resources would be disabled, like configuration for multiple speakers (5.1, 7.1, etc.).
