Re: Not everything is Windows
Rename a file in Terminal and Finder will faithfully treat it differently if the extension changed. That also goes for if you told Finder to show file extensions then rename a file with Finder changing the extension.
Here the malware seems to be an app bundle dressed up as an rtf file, and if you have extensions hidden (as they are by default) then you're not going to know unless you realise the context menu options and properties are appropriate for apps.
Not good design.