A suspected member of the Al Qaeda terrorist group, arrested in May last year in Germany, was found with a memory stick hidden in his underwear. Police discovered the stick contained a password-protected folder with pornographic videos inside it, but suspicious computer forensic experts thought there must be more. After weeks of analysis, they determined that one of the pornographic videos contained concealed documents detailing Al Qaeda operations and plans. The files were hidden in the video file through a process called steganography or concealed writing. The term steganography includes methods used for centuries, such as invisible ink, but now...