In this video I discuss how Korean Telecom (aka KT Corp) deployed malware to the PC's of 600k of their customers who were using bittorrent applications to share files with one another. [Mental Outlaw]
If this checks out, and it seems to, this is the craziest shit I've ever heard of an ISP doing.
Edit: Invidious video link - https://yt.drgnz.club/watch?v=iRjdjck3obY