Streaming Video Files
If you want any real level of protection you need to use a true streaming server. The big advantage here is that the file is not actually downloaded to the user's computer—it is seen only as a real-time stream and there is no file left on the user's hard drive.
Streaming video provides fairly good protection. It will stop most casual thieves dead—only those with determination and a bit of technical understanding will continue to try and steal the video.
The most common method of stealing streaming video is to use a video stream capture tool. This is an application that captures a video stream and saves it as a file. This type of theft is extremely difficult to guard against. Although there may be some defences, e.g. denying access to known capture utilities, this level of defence starts to become a losing battle. A thief who is dedicated enough to use a stream capture utility is probably dedicated enough to do whatever it takes to get the video.
Even if the thief can't capture the stream directly, they can always use a screen capture utility. This is an application that captures whatever is displayed on screen. They can define a certain area or window (i.e. the video screen), play the video and tell the utility to capture it. There really isn't much you can do to fight this, but even if you could...
Anyone can set up a video camera and point it at a computer monitor. Anyone with a few clues can remove flicker and get a reasonable result. There is absolutely no way you can stop them from doing this. Although it's a very uncommon way to steal video, it's a good illustration of the fact that thieves always have one more option than the webmaster.
