Newswise — The act of concealing data in plain sight is known as steganography. Since antiquity, clandestine couriers have used hundreds of steganographic techniques, including invisible ink, shrunken text, and strategically placed tattoos. A more modern approach, known as network steganography, leaves almost no trail, hiding communication in seemingly innocent Internet traffic. And because steganography programs use short-lived delivery channels—a Voice over Internet Protocol (VoIP) connection, for example—the hidden exchanges are much harder to detect.

About a decade ago, state-of-the-art programs primarily manipulated the Internet Protocol. Today, however, the most sophisticated methods target specific Internet services, such as search tools, social networks, and file-transfer systems. To illustrate the range of things that are possible, the authors present four steganographic techniques they have recently developed, each of which exploits a common use of the Internet: Skype, Bit Torrent, Google Search, and Wi-Fi networks.