Apple didn’t give us an overly obvious way to disable the iSight camera that’s built in to the iMac, MacBook, and MacBook Pro, which is a problem for some people that work in sensitive environments. Covering the camera with a piece of tape will do the trick, but in some work places, that isn’t enough.
You can completely disable your built-in iSight by moving a single file. Just move the QuickTimeUSBVDCDIgitizer.component file from System/Library/QuickTime to another safe location on your hard drive. Be careful what you move, because the System directory isn’t a particularly safe place to mess around in. Should you move, rename, or delete the wrong file, you could potentially render your Mac unbootable.
You have to authenticate as an administrator when you try to move QuickTimeUSBVDCDIgitizer.component, and it will copy to the location you are trying to move it to instead of actually moving. Once the copy is complete, drag the original to the trash.
Removing the iSight component file will disable the camera and prevent any application from using it. If an application does try to use the camera, you’ll see a dialog that says the device is in use by another program.
To return your iSight to its normal and usable state, simply put the QuickTimeUSBVDCDIgitizer.component file back.