CAUTIOUS COMPUTER USERS put a piece of tape over their webcam. Truly paranoid ones worry about their devices’ microphones—some even crack open their computers and phones to disable or remove those audio components so they can’t be hijacked by hackers. Now one group of Israeli researchers has taken that game of spy-versus-spy paranoia a step further, with malware that converts your headphones into makeshift microphones that can slyly record your conversations. Researchers at Israel’s Ben Gurion University have created a piece of proof-of-concept code they call “Speake(a)r,” designed to...