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Information Technology

Securely Deleting Sensitive Data on a Mac

Even after you have deleted files from your machine, they may still be recovered by special file-recovery software. If you have sensitive data on your machine and need to delete it securely, there are two methods to use:

Note: Mac OS can keep a copy of your files in a "Recovered Files" folder in the trash. If you have been working on encrypted files or other sensitive data and see this folder in your trash, you should use the Secure Empty Trash option to securely erase them from your computer.

Warning!  The following methods will PERMANENTLY delete the files in your trash and other files you have previously deleted.  IT will NOT be able to recover them afterwards!

Method 1: Secure Empty Trash

  1. Move the files into your trash (at the end of the Dock).
  2. From the Finder menu, select Secure Empty Trash. This may take some time, depending on how large the files are.

Method 2: Erase Free Space

If you have already deleted sensitive data from your machine, or just want to make sure that the files you have deleted are not recoverable, use this option. It will take a long time, so plan ahead if you need to use it. 

  1. Launch the Disk Utility Application, from Applications/Utilities on your hard drive.
  2. Select the name of your hard drive (e.g. Macintosh HD) in the left hand pane of the Disk Utility window.
  3. In the right hand pane, choose Erase Free Space. You may choose from Zero out Deleted Files, 7-Pass Erase of Deleted Files, or 35-Pass Erase of Deleted Files.

Note: The last two options will take 7 and 35 times longer than writing zeros; they may take a very long time. Zeroing the data will prevent normal recovery tools from being able to retrieve the data, while 7 times overwrite exceeds the Department of Defense standard 5220.22.

Contact CUS with any questions about securely deleting files from your Mac.