One of the nasty secrets of the computer world is that even when you delete a file, it isn’t really gone. Instead, the computer marks the space as available will overwrite it at some time in the future. But all of the data is still there, ready for anyone to look at it, provided they know how.

When it comes time to dispose of an old computer, this can be a major problem – especially if the computer held sensitive data like patient records, personnel reports or financial information. Short of smashing the hard drive with a hammer, the best way to destroy the information is by overwriting the entire hard drive several times with unreadable gibberish; a process known as scrubbing.

Instructions

Luckily, scrubbing a hard drive is a relatively easy thing to do. I prefer to use a Linux tool known as shred – which is also used by the Department of Defense, CIA, and State to hide secrets pertinent to national security. Shred is included as part of the Finnix system maintenance CD, which can be downloaded at:

http://www.finnix.org

The CD is distributed as an ISO file, which you will need to burn to a physical CD by using ISO Recorder, or DeepBurner. After you have burned a Live-CD, scrubbing the hard drive is a simple three-step process: 1) Boot from the Live-CD, 2) Retrieve the name of the drive to be scrubbed, 3) run the utility from the command line.

Step 1: Boot from the Live-CD

To boot from the Finnix Live-CD, place it in your CD-Drive and turn the computer on. You will need to access the one-time boot menu. For most Dell computers, you access the one-time boot screen by pressing and holding the F12 key right after turning the computer on.

After the boot menu loads, tell the computer to boot from the IDE CD/DVD drive. This is often the last option available. Press Enter. After a few moments, the Finnix screen below should appear.

Select the “Boot Finnix (x86” option and press enter. Finnix will launch a prompt similar to the one seen below:

Step 2: Retrieve the name of the disk to be scrubbed

At the command line, type the following:

fdisk –l

Fdisk lists all of the hard-drives that are currently connected to the computer. In the example above, there is only a single disk: the main internal hard drive. It is connected as /dev/sda.

Step 3: Run Shred from the command line

The final step is to run shred from the command line. Type in the following:

shred /dev/harddisk –f –v –z –iterations=6

Be sure to replace the words in italics with the name of the drive (from step 2) and press Enter.

The number of iterations can be whatever number you wish. The US Department of Defense uses 6 when it is scrubbing its computers, the CIA uses 25. Realistically, it is unlikely that any data can be retrieved after even one or two complete iterations. I personally like to use three.

The program will begin to run. For a moderately sized hard drive (100 GB), it should take between four and six hours if you use three iterations. As a result, this job should probably be run overnight.

Similar Posts:

• Backup, Share and Sync – Part 2: Hard Drive Preparation and Server Configuration
• Reclaiming Free Space from a Time Machine Backup
• Backup, Sync and Share – Part 4: Apple Time Machine and Samba
• Install Time Drive On Ubuntu and Other Debian Linux Distributions
• Back In Time (Part 2): Over the Network and Across the World

Tags: Privacy,Security
Categories: Computer
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