World War II

Steganography and its prevention were also prevalent in World War II. After the attack on Pearl Harbor, the United States enacted a censorship organization. This organization worked to think of ways that coded messages could be passed in the open, and took steps to stop them and destroy the code. Chess games were banned by mail; crossword puzzles were examined or removed from correspondence, newspaper clippings, as well as students' grades. At one point, knittings were closely monitored to prevent another Madame Defarge, who passed a number of secret messages during the French Revolution. Stamps were removed and replaced with ones of equal value but different denominations or numbers. Children's pictures were replaced, Xs and Os were removed from love letters, and, of course, blank paper was replaced and tested for invisible ink.

Censor regulations also prohibited sending any text that was unclear, had personal notes not related to the message, or were in a language other than English, French, Spanish, or Portuguese. Censors would often paraphrase messages, and cables ordering flowers forbade any mention of a flower species.

Mass media was also censored. Telephone and telegraph requests for special songs were not allowed, and mail-in song requests would be held for a random amount of time before being played. Personal ads were also censored, including ads for lost dogs. There were no more man-on-the-street interviews, as this could be something an agent could "accidentally" make happen. Children's Christmas lists were also censored.