When I read this, I thought it meant computer virus, and I kind of have already. It’s not technically a virus, because it doesn’t spread, but back in the Windows XP era I made a program called Teddy Bear. It would install itself when you plugged in a USB stick and log the user out. When they logged back in, a teddy bear would ask them to play a game. The user had a beat the computer at pong before they got their computer back. It would block task manager too, even. It did that by turning the task manager window invisible when it opened, and returning focus to the game. It also worked in Safe Mode, so there was not really an easy way to bypass it.

I found a reference to it on Wayback Machine: https://web.archive.org/web/20071022180854/http://sciactive.com/