Steganography is a process which involves hiding a message in an appropriate carrier for example an image or an audio file. The carrier can then be sent to a receiver without anyone else knowing that it contains a hidden message. This is a process which can be used for example by civil rights organizations in repressive states to communicate their message to the outside world without their own government being aware of it. Less virtuously it can be used by terrorists to communicate with one another without anyone else's knowledge. In both cases the objective is not to make it difficult to read the message as cryptography does, it is to hide the existence of the message in the first place possibly to protect the courier. The aim of this book is to investigate the background of steganography, discuss steganographic tools in common use and methods commonly implemented. The theory is also enhanced with a series of documented steganography java classes which implement many of the algorithms discussed.