Secure delete data (Rev: 1.0)

When you delete your files or empty the Recycle Bin from a computer, the computer merely removes the references of the file from the file system table. Your files are still reside on the hard disk until another file is created over it. Your deleted files can still be retrieved using data recovery software or by studying the magnetic fields on the disk platter surface.

To prevent your hard disk data from falling into those malicious hands before you thrown it away, you can either physically destroy the hard disk by smashing it with a hammer, or use software to write over your data several times so that it cannot be easily retrieved. The more you overwrite your data, the harder it is to recover it. The United States Department of Defense recommends overwriting a hard disk at least 7 times.


MAC Operating System

1) Boot up your respective MAC machine using the Cheetah (10.0) or Puma (10.1) or Jaguar (10.2) or Panther (10.3) or Tiger (10.4) or Leopard (10.5) or Snow Leopard (10.6) or higher version CD/DVD by pressing c during startup to boot from the CD/DVD.

2) Launch Disk Utility.

3) Select the correct hard disk. Then, click on Erase tab and click on the Security Options. You will be provided with a list of options to erase your data securely. You can try the 7-Pass Erase option which meets the United States Department of Defense standards for erasing magnetic media.


If you just want to securely erase external media or memory cards, you don't have to boot up from the MAC CD/DVD. Just go to your Utilities folder and launch Disk Utility. Select the desired external media and click the Erase tab. Click on the Security Options. You will be provided with a list of options to erase your data securely.


Windows Operating System

The recommend free software to use are

a) Darik's Boot And Nuke (DBAN) 1.0.7 or higher version. It can boot up from floppy disk, CD, DVD or USB flash drive.


b) Eraser 6.0.1 or higher version for Windows XP, Vista, Server 2003/2008. After installing it, you can securely empty your Recycle Bin by right-click on it and choose from its comprehensive list. The 7-Pass DoD option is recommended.

Eraser can also be used to securely erases files, folders and drives (including those external hard disk or memory cards). After you have deleted the files from your hard disk, right-click on the drive in the Windows Explorer and select "Erase Unused Space".


Mobile Phones

ReCellular has a comprehensive resource on secure data deletion from phones made by Nokia, Motorola, Samsung and other major brands.


Windows Mobile Smartphones

If you lose your Windows Mobile-based phone and it is synced to Microsoft Exchange, you can do a remote wipe out of your phone. As a precautionary measure, you can enter incorrect PIN a few times to erase the smartphone memory.

Smartphones like HTC Touch Diamond are preloaded with an application that can do a "full reset" of the device, restoring it to its default settings and deleting all data and applications that you have installed.


iPhone 3G

If the iPhone is configured for Microsoft Exchange ActiveSync, you can perform a remote wipe out on the device. If you have enabled the Passcode lock feature, 10 failed attempts to access your iPhone will trigger it to erase your data.


References:

[1] Today (21 November 2008, B11, Tech, Remove data that just won't go away)

[2] Darik's Boot And Nuke (DBAN)

[3] Eraser

[4] Apple