You're confident a trusted employee can't steal research information on your company's new anti-cancer drug or plans for its next acquisition. Physical and logical controls monitor just about everything that leaves the building or the network, even encrypted messages sent to unauthorized recipients. But what about the message hidden in the family vacation photo he emailed to his "cousin"? Steganography has just bypassed all your defenses.

Steganography (from the Greek root "staganos," meaning covered or secret), or stego, is the technique of hiding data in a host file. Historically, it's been within the purview of the military, criminals and researchers. In recent years, however, it's drawn a lot of interest from the business community, and with good reason.