Secure Disk Erase on a Mac


Secure Disk Erase on MacI recently upgraded an external drive of mine and sold the old one on ebay.  I tend to repurpose old drives until they are out-dated to the point that nobody would want them and then physically destroy them.  Initially, I was concerned about selling my drive to a stranger because I figured there would be a way they could recover my data, and in fact, there most certainly are ways to recover data “deleted” on a hard drive.  Fortunately, since 10.3, Apple has included in Mac OS, a built-in feature called “Secure Empty Trash” that ensures deleted files cannot be recovered.  This feature can be accessed by going to Finder > Secure Empty Trash.  This process takes longer to complete than the standard empty trash, but especially for sensitive files, it is worth it.

So what should you do if you haven’t been using Secure Empty Trash all along and need to securely wipe a drive?  There are two main options on the Mac.  The first is another Mac OS built-in feature accessible through Disk Utility (located in Applications/Utilities/).  Select the disk you would like to secure, then select the Erase tab.  Within this tab there is a “Erase Free Space…” option.  Here you can select the number of times you want to zero out the free space on your disk.  Depending on the number of times you select and the size of your free space, this can be a lengthy process, so plan appropriately.  The other option is to use Permanent Eraser, an open source solution to this problem.  I’ve never used this due to the convenience of the built-in Apple solution.  Please leave a comment on your experience if you’ve used Permanent Eraser.

Remember, if you’re going to get rid of a hard drive, be sure to securely wipe the device so that you aren’t giving someone an opportunity to access your personal information.  A recent informal survey indicated that 40% of drives sold on ebay had readily accessible information contained on them.  Be smart, securely erase!

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