“The urge to snoop is as old as time,” says Brian Hochman in Wired. Catherine de’ Medici, for example, installed specially designed ventilation ducts at the Louvre so she could listen in on anyone plotting against her. Archaeologists have unearthed “acoustical arrangements like these” dating back to 3000 BC. But it wasn’t until the 1940s that the invention of tiny electronic transistors made secret bugs good enough, and small enough, to become a serious tool for nosy spooks. These microphones, “smaller than sugar cubes and thinner than postage stamps”, could be secreted anywhere: from wall sockets and picture frames to packs of cigarettes, shirt buttons, lipstick tubes and lighters.
By the 1960s, as many as one in three divorce cases in major American cities “involved a conversation intercepted by a hidden microphone”. Amid widespread panic about the spread of the tech, a private detective “with a flair for the dramatic” was hauled up before Congress to explain what was going on. The professional snooper pretended to sip a martini throughout his testimony, but he’d bugged the olive in his glass. “At the end of the proceedings, he played back his opening statement for rhetorical effect.”