Israeli security researchers created a proof-of-concept code (malware) that converts typical headphones into microphones. Malware is disturbingly able to hijack a computer to record audio even when its microphone is disabled or completely disconnected from the computer. Attack works on practically any computer, running Windows or MacOS, and most laptops, as well, leaving most computers vulnerable to such attacks. The only way to deal with this issue is to redesign and replace the chip in current as well as future computers.
Source: https://thehackernews.com/2016/11/headphone-spying-malware.html