There’s one going around right now. I get about 4-5 calls a day.
The caller identifies themselves as representing “Microsoft Technical Department”. They go on, saying they have observed suspicious activity in your account or some such.
If you continue, they have you enter a few strokes and a whole list of items pops up.(about 25) They say that each item represents someone, somewhere, who is currently using your computer for their own purposes without your permission.