Web sites, ad feeds can show that "your computer is infected" so to get infected, YOU HAVE TO DO SOMETHING. Unless you are running an out of date browser on say XP I have yet to see a drive by infection.
The rest of your post reads as if the owner installed the bad things.
Have you ever heard of NINITE.COM?
Thursday afternoon my laptop got the usual "your computer is infected, call this number, supposedly from Microsoft" when I tried to click on a Yahoo news story about the upcoming NE storm. Machine was locked, couldn't do anything. Took it to expert computer friend who removed it. He removed Google Chrome as well, appeared to have rootkit stuck to it. Not sure yet if its OK or if it will have to be wiped. Its a Win 10.
Using desktop with Firefox, Win 7, put Malware Bytes on it, free premium trial. Today also went to Yahoo news and clicked on article, popup from Malware Bytes that they blocked suspicious activity.
Has anyone else had this experience with Yahoo news articles or have the hackers just decided to continue attacking my IP address?
My devices are NOT networked just in case such an event were to occur.