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How to Secure a Folder on a USB Drive in macOS

In today’s digital age, protecting your personal or sensitive files is essential. If you’re using a USB pen drive on a Mac and want to secure a folder, this guide will walk you through the steps. We’ll explore how to encrypt a folder using macOS’s built-in tools, ensuring your data stays private even if the drive is lost or stolen.

  1. Prepare the Folder
    • Place all the files you want to secure inside a folder on your USB drive.
  2. Launch Disk Utility
    • Open Disk Utility from Applications > Utilities or search via Spotlight.
  3. Create a New Disk Image
    • Click File in the menu bar, then select: New Image > Image from Folder....
  4. Choose the Folder
    • Navigate to the folder on the USB drive that you want to encrypt and click Open.
  5. Configure Encryption and Format
    • In the dialog box:
      • Set Encryption to 128-bit AES (recommended) or 256-bit AES (more secure but slower).
      • Choose Read/Write if you want to edit files later.
      • Provide a secure password and re-enter it (use a mix of upper and lowercase letters, numbers, and symbols). Do not lose this password, as it cannot be recovered.
  6. Save the Disk Image
    • Choose where to save the .dmg file (preferably on the USB drive itself).
    • Click Save and wait for the process to complete.
  7. Test Your Disk Image
    • Double-click the .dmg file to mount it. Enter your password to access the contents. When done, eject the image to re-secure it.

To add an extra layer of obscurity you can:

  • Rename the .dmg file to something inconspicuous, like “system_backup.dmg”.
  • Move it to a less noticeable directory on the USB drive.

The “Operation not permitted” error could occur. This one typically occurs on macOS due to permission restrictions, especially when trying to access certain folders or save files to specific locations (macOS restricts certain applications from accessing sensitive areas).
To resolve this issue you need to grant full disk access to Disk Utility App. Here are some steps to resolve the issue when creating an encrypted disk image:

  1. Open System Settings (or System Preferences on older macOS versions).
  2. Navigate to Privacy & Security > Full Disk Access.
  3. Click the lock icon (bottom left) and enter your admin password to make changes.
  4. Find Disk Utility in the list:
    • If it’s not listed, click the + button to add it manually.
    • Navigate to /System/Applications/Utilities/Disk Utility.app.
  5. Enable the toggle for Disk Utility.
  6. Restart Disk Utility and try again.

Securing your files on a USB drive in macOS is straightforward with the built-in Disk Utility tool. By encrypting a specific folders, you can ensure your sensitive data remains protected. Start securing your USB drive today and enjoy peace of mind knowing your files are safe!