According to New Scientist's Paul Marks, researchers at Poland's Institute of Telecommunications have developed a tool called SkypeHide, which is capable of embedding secret data in Skype calls.
"[Wojciech] Mazurczyk and his colleagues Maciej Karas and Krzysztof Szczypiorski analysed Skype data traffic during calls and discovered an opportunity in the way Skype 'transmits' silence," Marks writes. "Rather than send no data between spoken words, Skype sends 70-bit-long data packets instead of the 130-bit ones that carry speech."
"The Polish team's system hijacks these short snippets of data and replaces the bits with different info that they choose," writes Fast Company's Kit Eaton. "The Skype software ignores the 'silent' packets, but a suitable system can still decode the silent messages. As a bonus the entire setup is hard to detect and is capable of sending up to 1 kilobit per second of secret data of any type, be it text or video."
"Mazurczyk told me by email that his team are currently in currently in contact with some companies and 'may plan to commercialize SkypeHide as a Skype add-on,'" writes Slate's Ryan Gallagher. "The researchers are scheduled to present a prototype of their invention at a conference on steganography -- the art of writing hidden messages -- in France later this year."