One security and privacy feature of Mac OS X (includes Yosemite) that you might not know about is how to encrypt and password protect existing folders. The Disk Utility app allows you to create an encrypted disk image (and when mounted is called a “volume”) from an existing folder, thereby hiding the folder from prying eyes.
IMPORTANT: My suggestion is to use an obscure folder name when encrypting and password protecting existing folders – don’t use obvious names!
How to encrypt an existing folder:
- Launch > Disk Utility (use Spotlight or locate in /Applications/Utilities)
- Open Disk Utility – pull down > File menu and select > New and then > Disk Image from Folder
- Navigate to the folder you want to encrypt. Click > Image
- Set Image Format > read/write and > Encryption to “128-bit AES” (you can also use 256-bit AES but this will be slower to encrypt)
- Click > Where. This allows you to decide where to locate the .dmg disk image (volume) TIP: NEVER SAVE THIS FOLDER TO YOUR DESKTOP
- Click > Create – then set a password to access the folder (store this strong/long password in a password manager) – Password strength should be ‘Excellent’
- NOTE: Make sure to uncheck the “Remember password in keychain” this will stop anyone from accessing your folder
- Click > OK to create the disk image
- Locate the encrypted folder (disk image) and double-click or right click to open and enter your password
- You can also drag and drop and or cut and paste any files you want to this folder. Remember to delete the original files after completing the transfer
If you open Disk Utility and look for > Mount Point (bottom of window), this will show you the volume mount as well as file size; format (should be Mac OS Extended (Journaled) as well as number of encrypted files. When not mounted, the folder disk image will appear as a .dmg file (executable suffix).
Once finished with the disk image you can dismount the volume to hide it using Finder or Disk Utility. Make sure you do this if you leave your Mac in hibernation and or you decide to shutdown.