This is done using Steganography. The bytes in a binary file are change to store the hidden message. Though not very secure, it serves as a very simple tool to

This is done using Steganography. The bytes in a binary file are change to store the hidden message. Though not very secure, it serves as a very simple tool to fool human eyes. http://en.wikipedia.org/wiki/Steganography http://en.wikipedia.org/wiki/Steganography