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full-disclosure-uk: Re: [Full-disclosure] Disk wiping -- An alte

Re: [Full-disclosure] Disk wiping -- An alternate approach?

From: <Valdis.Kletnieks_at_nospam>
Date: Tue Jan 26 2010 - 18:26:58 GMT
To: T Biehn <tbiehn@gmail.com>

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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