The Tampering Alarm is an intelligent feature found on IP CCTV cameras which have a strong focus on security, such as tamper/vandal resistant IP cameras. The kind of cameras which are designed to be installed in exposed locations where there is a active threat of people interfering with it.
It's easy to set up. Once activated the camera will notify you if it has been moved, obscured, covered or sprayed with paint.
They way it works is simple. When the camera is first turned on it will take a few seconds to examine the scene. After the examination process is complete the scene is locked and any alteration to the scene can cause an alert. This does mean however that if the light changes drastically in a scene (such as turning a off a light) then the camera will generate a tampering alert. Some cameras have the facility to 'turn off alerts from dark images' so that it isn't affected by light changes but the downside of that is it will no longer trigger an alarm if the camera is covered or sprayed, only if it has been moved.
Tampering Alarms are a useful tool which provide instant feedback when a camera has been compromised, something which could take a CCTV operator a lot longer to discover.