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A few days ago I did some summer cleaning on my computer, moving a bunch of old files to an external Flash drive for backup and then deleting them from the computer. To make sure that no one could recover my old photos or videos, I used this program called Eraser to wipe the free space after I moved the files. I used the Guttman method (35 passes) to wipe the free space on my hard drive.

Is there any way someone could recover this data even after I wiped it with 35 passes? Let's say I sold my hard drive on Amazon and someone bought it. Would they be able to do it?

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migrated from Jul 18 '11 at 15:30

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Algorithm for recovering data after 35 passes: order Ryan's harddrive; wait for him to leave for the post office; break in and steal flash backups. – Shog9 Jul 18 '11 at 15:26
Regarding your backup to flash drive: I hope you wrote your files to an encrypted container or such. You can't delete the files there that easy with wiping as on a hard disk because of wear levelling. – ott-- Oct 21 '11 at 21:03
yes u can recover it.....thby using magnetic force microscopy (MFM)... – user103073 Oct 27 '11 at 4:32
@nee is actually on to something here, but most people do not have millions of dollars of AFM equipment lying around, so I think you're safe. – Shinrai Dec 13 '11 at 18:07

On modern mechanical drives, all data is completely gone after one pass.

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If that is true can you supply a reference? – user81238 Jul 18 '11 at 15:43
@B Tyler 1 pass makes all data gone to most people. There are theoretical recovery techniques but unless your hiding from some advanced government agency like Jon said, your good – TheLQ Jul 18 '11 at 15:50
One-pass data mixed with today's latest high-density storage platters makes this even more likely. Sure, this may not have been true in the mid 1990's when the Gutmann method was popular, but storage densities have increased thousands of times since then. – Breakthrough Jul 18 '11 at 17:12

The Guttmann method if applied properly and thoroughly should have rendered the data on the drive completely unrecoverable.

For the most part a far less comprehensive erase would be fine - Guttmann protects against attacks which are basically theoretical only and if even possible would likely beyond anyone but intelligence agencies and others with that level of skill and resource.

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The Gutmann method, while effective, only contains patterns applying to mid-1990's drives. There are far better, faster, and more efficient ways of wiping a drive these days. – Breakthrough Jul 18 '11 at 17:11
+1 even if you don't tell us what the 'better, faster, and more efficient ways of wiping a drive these days" are ;-) – Mawg Oct 13 '12 at 3:07

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