On Thu, Jul 03, 2003 at 12:50:01PM -0600, Matthew Pittard wrote: > How could someone access the information if you just reformat the hard > drive? Especially if you reformat it to a different file system like > NTFS?
The magnetic domains on the platter leave a resonant trace every time
they are re-arranged. There are techniques whereby the ``history'' of
what has been written can be reconstructed based on various signal
processing approaches. You have to have equipment that is capable of
reading more than just a ``1'' or a ``0'' off of the charge on the
platter; you need to know a precise quantity of the charge.
For example, in my suggestion earlier where I explained how to
overwrite the data with all 0's, it would be very easy (with the right
equipment) to measure the relative signal strengths of the domains on
the platter to determine if the previous value was a 1 or a 0. All
bit charges on the platter would be pushed down by a certain quantity.
Those that are pushed from 1 to 0 will go down by a certain quantity,
and those that are already at 0 will go down even farther.
Everything above a certain magnetic force would be a 1, and everything
below would be a 0. The data can be easily reconstructed, as long as
the equipment is sensitive enough. It is also possible to go back
over multiple writes in the history of any given bit using various
signal analysis techniques.
So, if your data is worth at least $10,000 worth of effort to recover,
you might want to overwrite it many times with alternating sequences
of 1's and 0's. If it is worth much more than that, you will want to
grid your platters down and incinerate them.
Mike
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Michael Halcrow | [EMAIL PROTECTED]
Developer, IBM Linux Technology Center |
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What's another word for synonym? |
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