Steganography is the art of passing secret information. Kapersky puts it this way: "Steganography is the practice of concealing information within another message or physical object to avoid detection. Steganography can be used to hide virtually any type of digital content, including text, image, video, or audio content. That hidden data is then extracted at its destination" [1].

This secretive process, which apparently dates back to ancient Greece, appears to have been named much later. The first recorded use of the term steganography was in 1499 by Johannes Trithemius in his Steganographia, "a treatise on cryptography and steganography, disguised as a book about magic" [2].

This article describes how attackers hide and extract potentially sensitive data. I will start by covering a sample of the types of steganography before looking at common ways of concealing information online. One common technique I'll describe in this article requires two message types: a container and a secret. The container conceals the secret from interception and ideally even conceals its existence.

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