Permanently Erase Data Off a Hard Drive

So you want to make sure that someone can't get their hands on your private files on a hard drive. Here are ways to render your data completely unreadable.

When files are deleted from a computer by emptying the Recycle Bin or Trash (or by reformatting), the operating system removes them from the list of files on the hard drive. However, the actual contents of the files remain on the drive until it is overwritten, either by use of the same space on the drive or by intentional data destruction. Data that has not been overwritten can easily be recovered with a few tools and a little know-how. This article covers methods of deleting data in such a way that the data becomes unrecoverable by anyone.

Steps

Boot and Nuke Method

This will allow reuse of your hard drive, the theory that your data is still recoverable by forensic analysis by well-financed governments, is based on a misunderstanding of a research paper from the mid 90s by Peter Gutmann, which looked at MFM floppy disks, not modern EPRML hard drives. Lifehacker describes the software that you will be using, Darik's Boot and Nuke, as "an open-source boot disk utility (read: works on nearly any computer) that supports a wide variety of disk wiping methods and operates from inside the computer's RAM, allowing it to scrub the disk thoroughly at a remove."[1]

  1. Download Darik's Boot and Nuke (DBAN) here. Two different versions (one for PCs and newer Macs, and the other for older Macs) allow DBAN to work on nearly every computer made within the last ten years.
  2. Burn DBAN to a CD. Since DBAN is an ISO file, you will need to use burning software that can burn ISO files (also known as CD images). Simply burning the file onto a CD in the ordinary way is not sufficient. If you don't see the "ISOLINUX" folder on the burned CD, it won't work and your hard drive will not be erased.
    • Windows 7 comes with the correct software to burn ISO files; simply double-click the file. If you are using an older version of Windows, download a program such as BurnCDCC if you don't have suitable CD burning software.
  3. Boot from the CD. Leave the CD in while you restart the computer you are erasing the hard drive with. If it doesn't boot up from the CD automatically, you will need to adjust the boot order in the BIOS. On an Apple Mac, you may need to hold down the "C" key while the computer starts up.
  4. Delete the data. You will need to select the disk to delete the data from (make sure it is the right one because you can't recover the data after it has been destroyed). You can choose how many times you want it to be overwritten and deleted. The default, 3-pass overwrite is far more than needed. Overwriting with "one pass of random data" is sufficient to prevent any recovery of data.

Physical Destruction Method

This destroys the hard drive, rendering it completely unusable (and therefore unreadable). You can also view more tips in How to Destroy a Hard Drive. Physical destruction is a good option for an archaic drive for which you don't have the necessary interface on a computer to connect it to, or if the drive will not reliably boot for you to run a software-based erase. It is also for those who want their data to be unrecoverable even under forensic analysis by governments.

  1. Remove the old hard drive you want to destroy from the computer or external enclosure (such as the outer case around a USB hard drive).
  2. Unscrew all the screws holding the top on. You will need the T-9 sized wrench for most hard drives. Sometimes there's an air seal. You will need to remove this.
  3. Destroy the platters. Once you get the top off you will see two or three stacked, silver disks (called platters). Put scratches on the surface of the platters with the Torx wrench. Now start smashing it with the hammer. Do this outside on a hard surface (such as concrete). Be sure to wear safety glasses to protect against flying debris. Glass platters (found on newer drives) will shatter. If you have a large hammer (a 10 lb sledge for instance): you can forgo opening the drive - a few good hits with a big hammer can split open the metal casing and mangle the platters, even on old full height 5.25" drives with metal (rather than glass) platters.

Selective File Wipe Methods[1]

Although not as good as the Boot and Nuke or physical destruction methods above, you can use these to erase only unused space while leaving your computer operable.

  1. Windows
    • Microsoft SDelete: Secure delete files, directories or sanitize free space.
    • Wipe File: Overwrites the specific disk space occupied by the file you'd like erased.
    • DeleteOnClick: Has a "Securely Delete" option to engage a Department of Defense 5220.22-M overwrite on the files.
    • Eraser: Can be scheduled to perform regular overwrites of empty disc space to catch orphan files.
    • WBD(Wipe Bad Disk): Can wipe disks with bad sectors.
  2. Mac OS X
    • Permanent Eraser: Can be used as an alternative to the "Secure empty trash" option. It overwrites the files 35 times.
    • Disk Utility: Integrated in Mac OS X. It has an "Erase Free Space..." function that writes over the unused space 1, 7, or 35 times.
    • srm: Terminal command that deletes and overwrites files making recovery impossible.
  3. Linux (Ubuntu)
    • Wipe Package from Ubuntu Unleashed: Adds secure multi-pass file deletion, like DeleteOnClick does in Windows.

Tips

  • Flame from a lighter or match applied directly to the disk platter will erase data.
  • You could also take out the platters and hand sand them or use a drill sander to make unique looking disks you can re-purpose for drink coasters!
  • The disks reflect light nicely and look great on a Christmas tree if you like a high-tech theme. Be creative!
  • Another alternative is a drill with a sheet metal or masonry bit—6 to 10 holes through the drive will be enough to make the drive unreadable.
  • The more hammer dents in the disk platters, the better.
  • Another way is to forget the unscrewing and just smash it until you get past the casing and to the platter.
  • On your next new computer (especially if it's a laptop), consider encrypting the disk with software such as FreeOTFE or TrueCrypt. Use a strong password to obviate the need to physically destroy the disk yourself at the end of its useful life. This might also protect the confidentiality of your data if your computer is stolen (if it's turned off).

Warnings

  • For your personal safety:
    • If using any source of fire, be careful! Fire is dangerous, and fumes can be toxic!
    • Be careful not to hit your fingers with the hammer.
    • Watch out for flying parts.
    • Don't microwave hard drives.
  • If you try to erase single files, you might not actually be successful because of the way modern computer file systems work. You should use the Boot and Nuke method and/or physical destruction methods if data security is really a concern.
    • Remember that once you do this, there is NO WAY to recover your data (especially with physical destruction methods).

Things You'll Need

  • Torx wrench set (including uncommon sizes such as T-9)
  • Hammer
  • Old hard drive
  • Eye protection such as goggles or glasses

Related Articles

Sources and Citations

  1. ↑ 1.0 1.1 http://lifehacker.com/5153684/properly-erase-your-physical-media
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