full-disclosure - Re: Disk wiping -- An alternate approach?

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Date: Tue, 26 Jan 2010 13:32:08 -0500
From: T Biehn <tbiehn@...il.com>
To: Valdis.Kletnieks@...edu
Cc: full-disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Re: Disk wiping -- An alternate approach?

I should have brought up the increased density problem Valdis, excellent points.

-Travis

On Tue, Jan 26, 2010 at 1:26 PM,  <Valdis.Kletnieks@...edu> wrote:
> On Tue, 26 Jan 2010 11:11:52 EST, T Biehn said:
>> Overwritten files require analysis with a 'big expensive machine.'
>
> Assuming a disk drive made this century, if the block has actually been
> overwritten with any data even *once*, it is basically unrecoverable using any
> available tech.
>
> Proof: In a decade of looking, I haven't found a *single* data-recovery outfit
> that claimed to recover from even a single overwrite.  Blown partition table?
> No problem. Metadata overwritten, data not? We can scavenge the blocks. Disk
> been in a fire? Flood? Run over by truck? Sure. We can go in and scavenge the
> individual intact bits with big expensive machines. Overwritten? <crickets>.
>
> Seriously - lot of companies can recover data by reading the magnetic fields of
> intact data.  But anybody know of one that claims it can recover actual
> over-writes, as opposed to "damn we erased it" or "damn the first part of the
> disk is toast"?
>
> No?  Nobody knows of one?  I didn't think so.
>
> 20 or 25 years ago, it may still have been feasible to use gear to measure the
> residual magnetism in the sidebands after an over-write.   However, those
> sidebands have shrunk drastically, as they are the single biggest problem when
> trying to drive densities higher.  You can't afford a sideband anymore - if
> you have one, it's overlapping the next bit.
>
> There *may* be some guys inside the spook agencies able to recover overwrites.
> But you don't need to worry about any evidence so recovered ever being used
> against you in a court of law - as then they'd have to admit they could do it.
> Just like in WWII we allowed the German U-boats to sink our convoys rather
> than let them figure out we had broken Enigma, they'll let the prosecution
> fail rather than admit where the data came from.
>
>



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