Many years ago when I was working in a small business, I began to notice that each time I walked into the office that I shared with the three other computer people who made up the IT department, this one particular guy (Joe, I'll call him here) would quickly toggle the display on his computer to a different window. I immediately recognized this as suspicious. When it happened two more times the same day, I was sure something was going on that I should know about. What was this guy up to that he didn't want me to see?