Hidden messages buried in VoIP chatter

Polish researchers have revealed the many ways you can hide messages within the bit stream of Voip phone calls.

If secret policemen didn't like Skype and its IP telephony cousins before, they'll really hate it now.

Burying hidden message in internet phone calls represents the latest evolution of steganography. Steganographic techniques for hiding messages have been around for as long as cryptography and have evolved with technology. Steganography once included messages hidden in wax tablets by the ancient Greeks and invisible ink and microdots on paper. Now it involves concealing messages within digitally transmitted images or sound files.

more at:
http://www.theregister.co.uk/2008/06/03/voip_steganography/