If you handle a lot of sensitive personal data on your PC, how can you be sure that it's completely gone?
It's worth considering the analogy of a sensitive message written on a piece of paper. To dispose of it, you could screw it up and put it in the bin. You could also shred it in several different ways, or you could totally destroy the paper by burning it or blending it in water to make a pulp.
In the first case, if you have access to the bin, it's pretty easy to fish the paper out and unscrew it. For shredded paper, if you have enough patience you could just about piece it back together, given time and a suitable sticky surface. For totally destroyed paper it's close to impossible to restore it and find out what its contents were.
There are similar disposal options available to you with a PC's data. You can delete a file, but it can easily be retrieved from the Recycle Bin. Even if you empty the bin, the data persists on your hard drive and a simple undelete utility such as PC Inspector File Recovery can retrieve it.
Even if the data has been overwritten, it's possible to use similar software to retrieve it. Therefore simple deletion is about as secure as throwing a piece of paper away.
Chop and change
For many, a digital shredding option will provide sufficient security. There are several such tools available, including Eraser.
These overwrite the data multiple times with random information, rendering it extremely difficult to recover. Given enough resources and time it may still be possible to retrieve the original data, but it will be hidden among enough noise for it to be a very expensive process.
ERASER-HEAD: If you're concerned about privacy, tools such as Eraser make it very difficult for anyone to recover deleted files
You can use Eraser to delete a list of files securely, or to erase the free space on a hard drive to ensure that it becomes extremely difficult to recover data that's already been deleted. If the hard drive is going to be changing hands, you may want to ensure that all data on it is shredded.
It's easy to overlook one or two files or forget the traces left by items such as the internet cache. You can do this by using Darik's Boot and Nuke; a boot disc that runs a shredding program to overwrite everything on the hard drive multiple times.
Just write the ISO file to a CD, boot from it and follow the instructions. Again, given unlimited resources and time, it may be possible to retrieve the data that was on a hard drive before it was nuked in this way, but it would be expensive and very time-consuming.
The final option is to destroy the hard drive containing the data. If the platters containing the data are completely destroyed, it's as difficult to restore the data as it is to get a piece of paper back from its ashes.
For a simple DIY solution, wipe the drive using Darik's Boot and Nuke and then drill through the body of the hard drive several times to destroy it.
BOOT-EM AND NUKE-EM: Darik's Boot and Nuke disc enables you to wipe a hard drive completely
Commercial solutions are also available, and Secure IT Disposals Ltd will mash a hard drive into granules. The page includes a video of a hard drive being shredded by the company's industrial machinery. It's hard to imagine data ever being recovered after this treatment.
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First published in PC Plus Issue 291
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Your comments (6) Click to add a new comment
mariasizer
May 26th 2011
6. After wipe out your hard drive you cannot recover your data back. Recently i sold my laptop to one of my friend and there are important data like credit card information or other important documents. Then i used the stellar file wipe software.Wipes traces of the installed applications and Web browser data including form fills, passwords, cookies, etc
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mobius
February 22nd 2010
5. @pete_l, this was my understanding as well. The last physics paper I read on it (can't remember where) they could determine the previous state of a bit on a magnetic drive because the orientation wasn't 100%. but this was with an atomic force microscope (the entire scans they did for the research only covered square microns in surface area) and it was with a brand new drive and assumed the bit had never been written to in its life before. In other words it couldn't even be used in practice and a used hard drive with one single (genuinely complete) overwrite pass would be unrecoverable.
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drmarten
February 22nd 2010
4. To gabethepilot,
Even if the Master File Table ( MFT ) or directory entries are wiped, it is still possible to recover data from a hard drive.
I have software that can do this which is a commercially available program. The more fragmented a file is though ( or parts overwritten) the less chance you have of recovering it in its original entire form.
Some recovery software looks at the internal structure of data found on a disk and tries to rebuild the file from a set of known file formats such as, for example: jpeg or bmp picture files.
The sure way to destroy hard drive data is to physically destroy the hard drive in any way you can think of, drill it, run over it with a car or steamroller, bend it or take it apart and break the platters.
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pete_l
February 21st 2010
3. This is a modern day myth
"Even if the data has been overwritten, it's possible to use similar software to retrieve it"
It can't. Not by a geek in his/her/its bedroom, nor by a government laboratory with an infinite budget and endless amounts of time. Once the data has been overwritten ONCE, it's gone forever and nothing will get it back.
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shambolic2000
February 21st 2010
2. You gotta wonder what a person has on their hard drive to make them want to drill through it to stop people seeing what was on there!
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gabethepilot
February 21st 2010
1. Even easier is to "purge directory entries" (in XP using for eg.: Directory Snoop) or "wipe MFT free space" (in Vista using for eg.: CCleaner {free] or BC Wipe).
Without these "indexes", no software will even be aware of it, ever having existed in the first place. It is also quicker than secure deletion / free space wiping.
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