My dad got taken by the "Hello this is Microsoft Support calling" scammers. They quickly got him to approve a remote connection to his machine and then they showed him a random registry entry as "proof" that his machine was infected with a virus. Which they just so happened to have the anti-virus for, for $300.
Dad was computer savvy, but by this point he was 80 years old and they flat-out took advantage of him. He had to mail me the machine so I could reload it.
Please - teach your parents to just hang up on these clowns. And to kill the browser process when they get popups trying to cause fear & doubt.