It refers to Remote Access Tools or Trojans (RAT) that can listen in or watch you via your microphone and cam.

Historical perspective: Mark Zuckerberg covers his laptop camera and you should too, said the New York Times in July, 2016. When the Facebook founder recently posted a photo of himself with his desk in the background, a Twitter user pointed out that the billionaire's laptop camera and headphones jack were covered with tape. Technology pundits surmised that Zuckerberg was concerned about hackers listening in or watching him by using remote-access trojans, a technique called "ratting." Security experts tend to back Zuckerberg. Trojans account for some 70 percent of all malware, and are relatively simple for hackers to spread by baiting users into clicking malware-infected links. A piece of tape may seem like a kludgey fix but it's a basic and cheap security safeguard against hackers scanning for vulnerable webcams.
NetLingo Classification: Online Jargon