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23. Clean hard drive before discarding that old computer

By Mark Alberstat

In January 2003, two of MIT's Laboratory of Computer Science graduate students published a paper outlining what they found on 158 used disk drives they purchased on the web and through swap meets. The revelations were startling and many people are thankful these two students were on the right side of the law, as they were able to recover about 5,000 credit card numbers and other personal information.

The two researchers, Garfinkel and Shelat, found that of the 158 drives, 129 were still functional and on 28 of these, little or no attempt had been made to erase the drive's information.

Government and industry throw away, or otherwise discard, thousands of drives each year. Although these drives should be cleaned, they are often not or are cleansed so poorly that the data is easily recovered with a few tools easily downloaded off the net.

Individuals, of course, also upgrade their machines. With Christmas coming, many people are thinking about getting a new computer for their home and doing away with that old 166 in the corner is collecting dust faster than it can process the latest spreadsheet or game.

Before you put the old PC on the curb, you may want invest some time in truly cleaning off the hard drive. The person going around picking up curb-side PCs could be looking for more than some reusable parts.

Many users believe that when they go through their hard drive and delete old and unneeded files, the data is gone. This is just not so. This simply makes the file unreadable to the operating system at that time. With a bit of work, and not much time, that file can be reassembled and read.

If you are about to toss out an old hard drive or computer, and want to totally cleanse the hard drive first, there are products on the market and freebies for downloading that may assist you in wiping clean your hard drive's slate.

To do this you need a program typically called a shredder. These programs cover your old data with random numbers or patterns, completely obliterating the previously recorded data. The US Department of Defense has written a standard for such data deletion and requires shredders to be run three separate times over the drive, each time different data must be written.

Remember that running a shredder over certain parts of the drive may not delete all sensitive data, as backup copies and swap file copies of this data may be in other hidden areas. If you truly want your data destroyed, shred the entire disk.

There are several freeware shredders that can be downloaded at various sites. One of the more complete downloads in this class is SourceForge's Eraser Project. Last updated in August 2003, this freebie is not a demo of a commercial version but is, in fact, the full product.

Another popular shredding tool is called Active@KillDisk. This tiny, 214k, file works on all Windows, Linux and Unix PCs. It is, however, a demo of the full commercial version and has some limitations, such as being non-compliant with the Department of Defense's standard and supports only one erasing method.

Mac users can try Jiiva's SuperScrubber software, which also adheres to the Department of Defense's standard for disk sanitation. However, there are no demos of this software available and if you want to use it, you will have to pay almost $30.00 (US) for the pleasure of deleting your information. - SourceForge's Eraser Project - SourceForge's shredder for Linux - Mac shredder software - Active@KillDisk

The Mousepad runs every two weeks. It's a service of Chebucto Community Net, a community-owned Internet provider. If you have a question about computing, email If we use your question in a column, we'll send you a free mousepad.


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Originally published 7 December 2003


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