I have an external drive (usb 4TB HFS+) I want to use without risk of anything being able to delete or modify its contents . Including the user trying to move, rename or delete files. Any idea how I would do this? ps Have tried this Right clicking on the drive and setting the permissions under 'Get Info' to 'Read only'. However this only restricts access to the root folder. I can still open up any folder on the drive and delete away.