Copy Control
Copy control becomes an important issue when distributing digital media, especially when the content is made available through public networks. There are two common approaches - making it difficult to copy it in the first place (it can never be made impossible), and marking the media so that it can be identified should it be copied or used inappropriately.

Copy Prevention
Copying is impossible to stop completely. Once the material has been received by the end-user and stored, then the data is in their hands, and with enough money and time any copy control mechanisms (software or hardware) can be by-passed. However, the more difficult and expensive it is to copy material, the less likely it is that the average user will do so. Tracking unlawful copying
Watermarking is a method of incorporating a unique mark into a digital file, providing a way of proving ownership of material contained in another file. However, it doesn’t prevent, or notify you when an unlawful copy has been made. It may be useful in preventing mass copying of the material - where the number of copies made and distributed increases the likelihood of finding out that the copying is being done.