For years, artists and art historians have been familiar with hidden messages lodged within paintings. The well-known and much-admired art historian Anthony Blunt (who in 1979 was exposed as a former Soviet spy and whose biography has been brilliantly written by Miranda Carter) had a gift for decoding such disguised messages. Today, intelligence officials must pore over photographs posted on the Internet, because al-Qaida terrorists are apparently using digital images to communicate with one another. Hiding orders and information in photographs is known as steganography and can, for example, be compared to watermarks you might find on paper, only far less visible. As Gina Kolata explains:
The idea of steganography is to take advantage of the fact that digital files, like photographs or music files, can be slightly altered and still look the same to the human eye or sound the same to the human ear. The only way to spot such an alteration is with computer programs that can notice statistical deviations from the expected patterns of data in the image or music. Those who are starting to look for such deviations say that their programs are as yet imperfect but that, nonetheless, some are finding widespread use of steganography on the Internet. For national security reasons some of these experts do not want to reveal exactly what they find, and where.
Al-Qaida might not only be using computer files, however. Indeed, Osama Bin Laden's TV appearances since Oct. 7 may convey hidden messages of their own. In a letter published by the Daily Telegraph, Rob Welham writes: "If it is feared that Osama bin Laden is sending 'secret messages' by way of his television appearances, one wonders what the significance is of the following. On his first appearance after the attacks on Afghanistan, he wore his watch with the face uppermost. In the most recent broadcast his watch had changed sides. He had, in addition, acquired a gold ring on the third finger of his right hand." What, however, is the significance of such alterations?