I just installed a new Monterey System on my USB-drive and booted from it. Then I noticed that I can open Applications, that I installed on my main System!

I know that during the installation of Monterey to the USB-drive I had to set the owner of the Disk, but I didn't think I would be able to delete all stuff of my main Disk then.

How is this possible? Am I even supposed to be able to do this? Isn't that a Security issue?

1 Answer 1


Now macOS follows a long heritage of OS X and Classic Mac OS of being able to open applications from pretty much whichever disk or location they reside (with spotlight being ever so happy to index them all for you).

So, this is expected and by design and isn’t necessarily a security compromise as much as an unwelcome complication or surprise.

  • If you have physical access to a Mac, you can read and erase things.
  • If you depend on not bringing a new OS to bear with its own admin accounts, you will want to look at firmware passwords and locks.
  • https://support.apple.com/en-us/HT204455

On the new Apple Silicon Macs, enabling FileVault will protect your entire internal disk and you don’t have to lock it down as much due to all the data being encrypted at rest always.

In practice, this is very disconcerting when you have dual boot systems on APFS and see two of every app from spotlight - perhaps one on Monterey, another Big Sur, etc…

  • This has cropped up in an earlier QA - apple.stackexchange.com/questions/414678/… & link from that, using fstab to prevent mount..
    – Tetsujin
    Commented Mar 28, 2022 at 16:59
  • Actually i have an Apple Silicon mac with file Vault enabled, just to be shure: I only can open all Applications on my main drive because my set my user as the owner the external drive?
    – fabolous05
    Commented Mar 28, 2022 at 17:02
  • Wonderful, then you have the simplest situation. No need for firmware lock, just protect your admin accounts and you can run Apps when you can see them, @fabolous05 and maybe check if TinkerTool is of interest to handle blocking mounts.
    – bmike
    Commented Mar 28, 2022 at 17:41

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