How to Erase Files Securely

Chris Pirillo — Sun, 11 Nov 2007 04:40:39 +0000

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A community member wrote in to ask how to completely zero out data on his Mac before upgrading to Leopard. Fortunately, this feature is built right into OS X. There’s no need to install anything to completely get rid of files and folders.

We’ve talked before about deleting files from your computer. When you delete them, they aren’t really gone. They are moved to a different folder (recycler or recycle bin). It may be treated differently by the Operating System than a normal folder, but it is indeed right there still. In order to really delete these files on Windows, you’ll need to use something like the free Eraser program. It uses Gutmann’s Algorithm’s to completely remove all traces of a file from your computer, and overwrite the space that was occupied by the file.

In your Mac, you can use the Finder menu, and select “Secure Empty Trash”. When you use this command, it deletes all traces of files from your hard drive, preventing them from being recovered by anyone. It is good to note that you can NOT recover files once you’ve used this feature, so be SURE you want them to be gone permanently before using.

If you have only used Empty Trash (not Secure Empty Trash) to delete files before, free disk space will still be on your hard drive. To erase all free disk space, and thereby remove all traces of files that you deleted previously using the Empty Trash feature, you should use the Macintosh Disk Utility feature (located in the Applications folder) to remove this space as follows:

Open the Applications folder
Click the Utilities folder
Double-click Disk Utility
From the left-hand column, click the disk, volume, or image from which you want to erase free space
Click the Erase tab
Click the Erase Free Space button
Click the radio button in front of the 7-Pass Erase of Deleted Files option
Click the Erase Free Space button

If you see a system message that says you are running out of disk space, you can ignore it. When the utility is complete, your hard drive will have the same amount of free disk space available as before you ran the utility.

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How to Erase Files Securely

Chris Pirillo » securedelete

How to Erase Files Securely