  Steganography is a general term referring to all methods for the embedding of
additional secret content into some form of carrier, with the aim of
concealment of the introduced alterations. The choice of the carrier is nearly
unlimited, it may be an ancient piece of parchment, as well as a network
protocol header. Inspired by biological phenomena, adopted by man in the
ancient times, it has been developed over the ages. Present day steganographic
methods are far more sophisticated than their ancient predecessors, but the
main principles have remained unchanged. They typically rely on the utilization
of digital media files or network protocols as a carrier, in which secret data
is embedded. This paper presents the evolution of the hidden data carrier from
the ancient times till the present day and pinpoints the observed development
trends, with special emphasis on network steganography.

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