TLDR: a “trader” is anyone who makes money via the Apple App Store

Developers who make money from the ‌App Store‌ through either an upfront purchase price or through in-app purchases are considered traders, regardless of size.

I wouldn’t worry about this unless it’s a game or software, and even then, the non-pirated version probably has DRM that’s somehow worse than malware.

Now if your video file ends up being a password protected rar and you don’t already know the password, just delete it and find another video torrent.

Which Linux did you install? How old is your installation? Do you have auto update enabled or do you regularly install updates?