Way back in ~2008 I wrote the Newton Virus https://www.everita.com/how-the-newton-virus-was-made + https://www.youtube.com/watch?v=eh75j6OHhRc (sorry for the broken images, need to update that site). Between that and using a hidden API to take screenshots of each individual element on your desktop (from icons, to taskbar, to windows) the effect was pretty believable. One of the most fun (and frustrating) projects I ever worked on.