Israeli Researchers Turn Speakers/Headphones Into Eavesdropping Microphones

In the current age, even the most secure software and the best security practices might not be enough to prevent someone from being spied upon. Researchers continue to find novel and inventive ways to gather more data on everyday computer users, and the latest research from Israel’s Ben Gurion University is exceptional in this regard.

Using software alone, Mordechai Guri, Yosef Solewicz, Andrey Daidakulov, and Yuval Elovici were able to convert a given pair of headphones or speakers into Orwellian microphones beyond the user’s control or ability to patch. Their method [PDF] exploits a flaw in RealTek hardware chips, which are one of the most widely used chips in motherboards around the world. Companies like Dell, HP, and Compaq regularly utilize RealTek’s industry standard audio chips in their products. Beyond that, motherboards sold to consumers wishing to build their own systems often also include the hardware.

A simple patch or firmware upgrade will not fix this flaw, making the exploit particularly delightful to intelligence agencies, profit-motivated hackers (think boardroom conference calls), and others. Basically, anywhere a computer has an audio output, which in the case of laptops is everywhere, audio can now be intercepted and then relayed with roughly the same quality as if a microphone itself had been compromised. The images of people like Mark Zuckerberg covering up their webcam and microphone with electrical tape now seem trivial.

Jack re-tasking – the process of converting an output jack to either an input or a two-way port – has long been a possibility, but few developers make use of it. Most laptops and desktops will have separate ports for each, while smartphones and the like often require hardware that can do both. But the innovation on the part of Ben Gurion’s researchers involves making any regular output hardware capable of doing as much with only software. They write:

The fact that headphones and earphones are physically built like microphones, coupled with the fact that an audio port’s role in the PC can be altered programmatically from output to input, creates a vulnerability which can be abused by hackers.

The researchers noticed that the design of most audio input and output hardware was basically identical at the metal, drawing the following illustration for clarification:

Source: Ben-Gurion University of the Negev Cyber Security Research Center
Source: Ben-Gurion University of the Negev Cyber Security Research Center

One saving grace is that the audio output device must be “passive,” or unpowered. This means that if your speakers require power to work, they are not currently able to use these to listen to you. However, the vast majority of laptop speakers and earbuds are, by nature and necessity, passive. The researchers note that while they focused on RealTek codec hardware because of their popularity, other manufacturers also have the ability to retask jacks, which is the heart of the exploit.

While this may seem scary at first, it should be noted that, like anything else on your computer, audio input and output are data. They can therefore be encrypted with keys that are local to the machine, and it would seem that this new exploit opens up a new avenue of research for cryptographic researchers to institute audio encryption in the same way that full-disk encryption has become normalized.

Here is a demonstration of the method in action:



P. H. Madore has covered the cryptocurrency beat over the course of hundreds of articles for Hacked's sister site, CryptoCoinsNews, as well as some of her competitors. He is a major contributing developer to the Woodcoin project, and has made technical contributions on a number of other cryptocurrency projects. In spare time, he recently began a more personalized, weekly newsletter at