Securely erase a drive

Securely erase a drive
Mac Tip #232/01-March-2006

It’s all very well chopping up old floppies to destroy confidential data they contain, but you’re not going to want to smash up the hard drive you’re currently using just to wipe out some confidential client information.

These days you have a couple of options: erase the whole drive or securely empty the Trash.

For one thing you can wipe the whole hard drive and reinstall everything you want to keep. This is a drastic step, but it may be suitable for you.

If you need to erase a drive inside your Mac you’ll need to start up from the System CD or DVD. To erase an external drive just plug it in.

Warning: the following will delete all files from the drive and you will not be able to get them back.

Plug in the external drive and start up Disk Utility from the Utilities folder in your Applications folder.

Select the drive you wish to erase from the list on the left of the Disk Utility window. Click on the Erase tab and click on Security Options…

A 35 pass erase takes a long time.

A 35 pass erase takes a long time.

Now choose the level of security you need. There are explanations below each one. Note that the time required to carry out the action increases as you go down the list. Click OK.

Next double check you have the correct drive selected in the list on the left of the window, be sure you really want to totally destroy all information on that drive and click the Erase button.

Now you’ll see a warning that the operation will destroy all information. It’ll specify the disk and ask for confirmation. If you’re totally sure, go ahead and click Erase.

I erased a tiny little 2 Gigabyte external firewire hard drive using my old Titanium Powerbook. After one hour it had completed 7 of the 35 passes. All up it was 5.5 hours to complete the task. Time taken can be affected by many factors, but clearly this ultra secure option can take a very long time.

This was a drastic and time-consuming action. Next week I’ll cover the other option: Securely empty the Trash.

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