Hardware or software that prevents a malevolent program from capturing the user's face and surroundings as well as any verbal activity. A hardware Webcam blocker is a cover that slides across the camera lens; however, software blockers turn both the camera and microphone off until the user turns them back on. See Webcam
The simplest approach to blocking the camera is a cover that sticks onto the Webcam and has a slider that covers the lens. However, covers do not prevent a hacker from listening via the microphone.