WebCam On-Off is a free Windows tool which can toggle your webcam driver on or off as required.
This offers a little extra protection from "webcam hijacking", where someone hacks into a webcam and can monitor its images without permission.
The program interface is very simple. Launch it, a status icon indicates whether the driver is on or off, and you click "Enable" or "Disable" as required. Easy.
If you don't want to manually toggle the setting each time, then WebCam On-Off also provides a command line interface. Run "Webcam.exe /on" or "Webcam.exe /off" and the driver is configured to match, so you can launch the program from a shortcut, a script, a scheduled task, whatever you like.
This isn't in any sense a real security solution. If someone is able to penetrate your PC from the outside world, has placed a trojan on your system, maybe broken a weak password, then that's the real problem. Stopping them using your webcam isn't going to help much if, say, they just capture your keystrokes instead.
Still, WebCam On-Off does offer a minimal extra layer of protection, and it might be useful for other reasons, like making it harder for your kids to use the webcam without permission.
Version 1.2 brings:
1.[improved] – Webcam preview screen and settings button design
2.[Added] – P (preview) Parameter for Cmd command
WebCam On-Off provides a simple way to prevent a webcam being used without your permission. It's by no means infallible, but it's tiny, adware-free and easy to use, so safe to try if you're interested.