According to Wikipedia, "Steganography is the art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message".
http://en.wikipedia.org/wiki/Steganography

When a eBook is successful, some people buy it, then share it for free on their sites. When the author finds out that his book was shared illegally, he can send a DCMA notice to the sites, in the hope that the owner of the site...