Maybe 10 years ago now (showing my age) - I was evaluating MS Systems Management Server for the company I worked for. I discovered the remote desktop assistance feature. ;) Cut a long story short - I installed the client on a machine in the office next door while everyone was at lunch. When they came back from lunch I sat in my office randomly taking control of the mouse and opening/closing applications on the desktop. I could hear lots of discussion about a possible virus until I opened Notepad and type "No virus - it's me!". I just about escaped with my life that day.