I was once pulled in to consult on a new unix system that was being connected to a bank's mainframe. The operator I was working with, who had worked on mainframes his entire career, hesitated and said he needed to call someone because he couldn't remember the password into the unix system. When they didn't answer, I asked if they wanted to try 'root', or something. They did. It worked. Stunned silence followed. They wanted to know how I knew that. Nobody was supposed to know that.