the Wall of Sheep
loresecurityevents
The DEF CON installation that sniffs the conference network for credentials sent in the clear and projects the partially masked usernames on a giant screen, for everyone to see and laugh at.
It is education by public embarrassment, and it worked: a generation of professionals learned what a plaintext protocol really means by watching colleagues appear on the wall. The Wall is also a quiet historical record of encryption's spread - it used to fill up in minutes with mail and web logins, and the rise of ubiquitous TLS slowly starved it. DEF CON's broader folklore lives in the same spirit: the hostile network you are warned never to trust, the badge that is a hardware puzzle, and the Spot the Fed game.
Also known as: wall of sheep, defcon wall, sheep wall