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By Andy Thomas
What's the easiest way to secure your hard-disk before recycling your PC?
In the past, when it came to retiring an old PC, I would either give it to a friend
or sell it on for a few bucks. Of course, I'd make sure I deleted all my personal
files and, for good measure, I'd empty the Windows Recycle Bin as well.
I realized that by deleting files, I wasn't really destroying the
data, rather I was simply telling Windows that the files weren't there any more so that
the disk space could get re-used. But I kind of figured that it would be unlikely
anyone would go to the effort of recovering my files, and in any case, the data would
eventually get overwritten as the computer was used.
So I figured.
It was brought home to me just how naive I've been when I stumbled up this
news article.
The article is rather dated now, but its message could not be more current, and
it is this:
Wipe your hard-disk before disposing of your PC
Recycled computers from all over the developed world find their way in to
the West African second-hand PC market where identity fraud is rife. Unless the
underlying data on the hard-disk was effectively destroyed by overwriting, it is
trivially easy to recover files that the PC's previous owner thought they deleted.
So if I wasn't utterly convinced of the need to make sure I don't leave any
data lying around the next time I dispose of a PC — I am now.
But what, actually, is the easiest way to do this?
Well, the surest way is to physically remove the hard-disk and destroy it,
preferably by launching it into space in the general direction of the Sun —
it's amazing just how indestructible modern hard-disks are. The application of
an electric drill through the casing and platters is a slightly more realistic
proposition, however, and should generally do the trick. If you're sending the
computer to be recycled, I actually think this is the best option.
Alternatively, if you want to leave your hardware intact, you could
securely erase the hard-disk of all its data. Simply reformatting is not
normally sufficient to do this. Instead, you need a bootable utility to ensure
that you properly erase the disk of everything, including all formatting and
boot information.
A well known free utility to do this is
"Darik's Boot and Nuke", which will
create a bootable CD or USB which you can then use to wipe any attached hard-disk,
including the computer's primary drive.
I haven't tried Boot and Nuke myself as I don't want to render my PC
useless just yet. However, I suspect that the process of properly wiping a modern
hard-disk will take a considerable amount of time.
If, however, you want to sell or give your computer away in working order,
both of these solutions have a slight catch associated with them. With
Boot and Nuke, at least, you have the option of re-installing an operating
system using the installation CD that came with the computer — you do have one,
don't you?
All this is very time consuming though, and if all you want is shut of
your old PC, it will feel like a lot of effort.
So here's a practical, though less secure, alternative to wiping
your operating system:
- Go through your hard-disk and individually delete all your personal files.
- If the PC is used by multiple users, delete any additional user accounts.
- Be sure to empty the Windows Recycle Bin when you have finished. This is
important — until you do this, the files won't even be considered "deleted".
- Now, use a "file wiper" program to overwrite the disk's free space,
thus destroying the content of the files you've just deleted, but leaving everything
else intact. Microsoft provides a free command-line utility which will do this
called SDelete.
You should make the effort to remove all temporary files used by your applications, such
as your browser's cache and stored password files. Ideally, you should also
disable the swap file before wiping the free space, as this will allow the area
of disk containing swap data to be overwritten.
This method will not be as secure as destroying everything on the disk, because
in all probability, it is likely that you will miss something. So, if your disk was
used to hold highly sensitive data, it's better to be safe and launch it into the Sun
on a rocket.
Copyright © Andy Thomas
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