Steganography

/ˌstɛɡ.əˈnɒɡ.rə.fi/ · Noun · Security & Infosec

Definitions

The practice of hiding a message inside an ordinary-looking carrier so that its very existence is concealed, as distinct from cryptography, which makes a message unreadable but obvious. Digital steganography typically embeds data in the least significant bits of image or audio samples, where small changes are imperceptible, or exploits redundancy in file formats, network protocol headers, and unused metadata fields. Because the carrier looks unremarkable, steganography defeats systems that flag encrypted traffic as suspicious, which is why it appears in both censorship circumvention and malware command-and-control. The countermeasure is steganalysis, which looks for the statistical fingerprints embedding leaves behind rather than for the hidden payload itself. The two techniques are often combined: encrypt first, then hide the ciphertext, so that discovery still yields nothing readable.
In plain English: Hiding secret information inside normal-looking files like photos or music, so nobody even knows there's a hidden message.

c. 440 BCE: Herodotus describes the first known steganography: a Greek shaving a slave's head, tattooing a message, and waiting for hair to regrow
1499: Johannes Trithemius writes 'Steganographia,' giving the art its modern name from Greek steganos (covered) and graphein (writing)
1990s: Digital steganography tools emerge, hiding data in image and audio files by manipulating least-significant bits