Erasing your hard drive

Why it's important

Before a computer leaves your possession, it's a very good idea to wipe the contents of the hard drive.

Otherwise, sensitive information such as passwords, emails, private documents, financial details and software licenses could easily fall into the wrong hands.

Simply deleting the files or formatting the drive is not sufficient protection, as these merely mark portions of the disk as unused, without actually erasing the data. Software tools exist that can easily recover files under these circumstances.

To prevent data from being recovered, you need to use a specific disk-wiping tool that not only overwrites the data, but does so with non-predictable patterns so that the previous data cannot be recovered, even through with advanced forensic analysis.

This may sound like overkill, however older machines at CSE are sometimes donated outside the university, so the goodwill of subsequent users cannot be assumed.

Wiping your CSE computer

If you are leaving CSE, and are using a CSE-provided machine, we prefer that you securely erase your hard drive yourself before you leave.

This ensures that sensitive information does not remain on your machine, 'unowned', after it leaves your control.

It also serves as final confirmation that your machine can be reallocated or disposed of, with no need to archive the contents of the machine before doing so.

To do this:

  • Back up any files you want to keep, onto your own removable or online storage, and then disconnect the machine from that storage.
  • Send email notification to System Support that the machine is being wiped.
  • Start the erase procedure as detailed below.
  • Do not shut down the computer after the wipe has finished - we need to see the wipe-complete screen in person before we can reallocate the machine.



Dariq's Boot and Nuke, or DBAN as it's known, is a freely-distributable utility for PCs.

It's distributed as a bootable CD image, which you can either download from the Official SourceForge repository, or borrow from System Support in K17-111.

After booting from the disk, DBAN presents you with a list of erasure methods:
DBAN wipe methods
and a list of disks that can be wiped.
DBAN disk selection

We recommend the DoD Short method as being both reasonably fast and acceptably secure. Select this, then the disk(s) you want to erase, and press F10 to start.

Depending on the speed of the computer and the size of the disk, this can take several hours to complete.

OSX Disk Utility

For Macintosh computers, the easiest way to securely wipe the drive is to use the Disk Utility program that comes with OSX.

OSX cannot wipe the drive that it has booted from, however, so in order to erase your system disk, you will need to boot from the OSX install DVD that came with your machine. If you don't have one available, System Support can loan you one for the purpose.

To do this:

  • Insert the OSX DVD
  • Reboot your machine
  • Hold down the C key as your machine starts up, and select the OSX install disk to boot from.
  • Click 'OK' and 'next' as necessary through the screens that appear, until a menu bar appears at the top of the screen.
  • From the 'Utilities' menu, select 'Disk Utility'.
  • Select the entire hard drive from the pane on the left.
  • Click the 'Erase' tab: Erase tab
  • Click the 'Security Options" button: Security options
  • Select '7-Pass Erase', and click OK
  • Click 'Erase', and confirm when prompted

This can be a slow process, potentially taking several hours to complete for a large drive.

Last edited by robertd 09/12/2016

Tags for this page:

wipe, erase, DBAN, HDD, drive