There are only two long term solutions: - an anti-vir scanner which constantly monitors all your files, hogs resources and plays the game of cat & mouse - Prevent users from installing software that wasn’t from the Mac App Store, just like on iOS.

The last is a nuclear option and not practicable for a professional desktop system. But I would like this as a configurable option for my parents. (Withholding the admin password from them is another possibility, but, well, see the article)