I found this article pretty interesting on how folks in the 1980’s in South Africa where hiding communications to others via the phone (touch tone buttons).
https://www.schneier.com/blog/archives/2013/12/operation_vula.html
I found this article pretty interesting on how folks in the 1980’s in South Africa where hiding communications to others via the phone (touch tone buttons).
https://www.schneier.com/blog/archives/2013/12/operation_vula.html