How To Securely Wipe a Hard Drive

There are many reasons why you might want to securely wipe a hard drive. You might be selling it, donating it to a friend, you might be recovering from malware or virus or you may be disposing of the computer entirely. You don’t want any of your private data to get into the wrong hands so securely wiping the drive is what you need to do.

You have several options if you need to securely wipe a hard drive. You can use the operating system, use free software, take it to your computer store or physically destroy the drive. I’ll cover the first two options as the second two should be obvious.

Delete is not enough

Simply deleting files or formatting the hard drive is not enough. When you hit Delete or Format, all your operating system does is delete the index telling it where a particular file is stored. This is then interpreted as empty space by the OS but the actual data is still intact. It will remain intact until it is written over.

This offers an obvious security risk. Anyone with the right data recovery software could buy your hard drive, recover those files and access all the data you thought was deleted. This has happened quite a few times in the past, not just home users, organizations too. Some of them very high profile organizations!

Format is enough

If you just want to wipe a hard drive and are keeping the drive in the computer or as a spare, you can use the format tool in your operating system. As long as you are not allowing anyone else to physically access it, secure wipe isn’t necessary. I would still suggest a secure wipe if you are recovering from a virus or malware though, just in case.

In Windows:

  1. Select the hard drive in Windows Explorer.
  2. Right click and select Format.
  3. Select NTFS as the file system and Quick format as the mode.
  4. Select Start to begin the format.

In Mac OS:

  1. Select the Disk Utility from Applications and Utilities.
  2. Select the drive from the left menu.
  3. Select Erase from the top menu.
  4. Enter a name, format and scheme.
  5. Select Erase.

In both operating systems, this will render data from the disk inaccessible but will not securely wipe it.

Use the operating system to securely wipe a hard drive

The simplest and cheapest method to securely wipe a hard drive is to use the operating system or free software.

In Windows:

  1. Open a CMD window as an administrator.
  2. Type or paste ‘format C: /fs:ntfs /p:1’ and hit Enter. Where you see ‘C’, change to the drive you want to wipe.
  3. Type ‘Y’ to confirm when you see the warning.

The command first formats the drive and creates an NTFS file system. It will then overwrite the entire drive with zeroes to prevent software data recovery. You can add another pass for extra security if you like by changing ‘p:1’ to ‘p:2’ or ‘p:3’. I tend to use two passes just to make sure.

In Mac OS:

  1. Repeat the process above to step 4.
  2. When you name the drive, select Security Options.
  3. Slide the Security Options slider to Most Secure in the popup window.
  4. Select OK.

Selecting Security Option 4 will securely wipe the hard drive to US Department of Defense (DOD) 5220-22 M standard. That should be good enough for most people!

Use DBAN to securely wipe a hard drive

DBAN, Darik’s Boot And Nuke, is the most reliable, secure way to wipe a hard drive for free. It is easily equal to many very expensive data security programs and is free and open source. You will need to download the file and burn it to a DVD or USB drive before use but aside from that is very simple to use.

  1. Back up any data you don’t want wiped.
  2. Download DBAN and install it to a DVD or a USB drive.
  3. Disconnect any other hard drives that you don’t want to wipe including your boot drive.
  4. Boot your computer from the DVD or USB.
  5. Press Enter at the blue DBAN screen to load into interactive mode.
  6. Select the drive from the list in the next window by pressing space.
  7. Double check you have the right drive.
  8. Hit F10 to begin the process.
  9. Wait for the black Pass screen to signify completion.
  10. Unplug the DBAN media, reconnect your hard drives and reboot your computer.

DBAN is the nuclear option if you want to securely wipe a hard drive but there is nothing better for getting the job done!

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