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Flash drives dangerously hard to purge of sensitive data

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Bahamut
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Flash drives dangerously hard to purge of sensitive data

In research that has important findings for banks, businesses and security buffs everywhere, scientists have found that computer files stored on solid state drives are sometimes impossible to delete using traditional disk-erasure techniques.

Even when the next-generation storage devices show that files have been deleted, as much as 75 percent of the data contained in them may still reside on the flash-based drives, according to the research, which is being presented this week at the Usenix FAST 11 conference in California. In some cases, the SSDs, or sold-state drives, incorrectly indicate the files have been "securely erased" even though duplicate files remain in secondary locations.

Full story here

Apparently, encryption is the only way to go and even then, you might have trouble.

John T. Haller
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Not Surprising

This isn't really too surprising. We've had warnings about this on the Eraser Portable and Eraser Drop Portable this whole time, and it's been discussed in the forums previously.

Sometimes, the impossible can become possible, if you're awesome!

Bahamut
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I remember discussions on how

I remember discussions on how single-file erasure is extremely difficult, if not impossible, on flash drives, but an interesting thing to note from the article is how SSDs can retain data after multiple full-disk overwrites (and that each pass takes days).

Vintage!

John T. Haller
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Yeah

I had thought a full disk eraser would get enough of files to make them unrecoverable. I've updated the warnings to make it more clear.

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OliverK
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Obviously, they were not

Obviously, they were not practicing secure drive destruction.

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Simeon
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hahaha

Kinda runs contrary to the normal way people want to use drives: recurringly! Smile

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EspaÑaks (not verified)
Noticed

Therefore, the drives have some more real space than the one you are told if they can save so much data even if overwritten?

Blum Sure it gets corrupted, but the data **is** there.

ottosykora
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this is by design so

as said many times, the file system or simply the data storage organisation of a flash device has little common with the file systems our operating system understand. The controller inside provide us with kind of virtual file system with the 'look and feel' of a magnetic hard drive, this just for the purpose we can use it on our operating systems which are 'used' to such rotating magnetic disks.
As we have no direct access to the file system of the flash media, we are not able to make there any changes.
The only way to kind of destroy data, might be to overwrite whole space with idle data, but still 'spare' blocks and other equalizing blocks are not simply to be accessed unless one can operate the controller directly on low level on the flash side. This has to be done this way, since particularly MLC cells are not that reliable and so enough spare blocks need to be provided.
And again, all our erasing ways done by software, are based on ours operating systems file system and structure, simply based on magnetic rotating disks as we use them for decades. So we do lot of operations on the level of operating systems language and on the machine language the flash understands.
Our OS thinks in file allocation table, files being stored in chunks on sectors with numbers so we can find them again. We can not access anything else, so all our software is not able to do anything else in general.

On the other hand, it is not so simple to recover data from the flash as it is from the magnetic drive, particularly when filled with idle data and the file system of the original data being destroyed.

Otto Sykora
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sja5164
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Best way to delete

The best way to make sure that your information is completely and irrevocably gone:

Take the thing out back and put a few bullets through it.

Smile

Nerdy Redneck

Rapscallion
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Interesting...

Found the following at http://www.guru3d.com/article/ocz-vertex-2-ssd-review/5

Windows 7 and the SSD TRIM feature

Windows 7 and Windows Server 2008 R2 support the TRIM function, which the OSs use when they detect that a file is being deleted from an SSD.

When the OS deletes a file on an SSD, it updates the file system but also tells the SSD via the TRIM command which pages should be deleted. At the time of the delete, the SSD can read the block into memory, erase the block, and write back only pages with data in them. The delete is slower, but you get no performance degradation for writes because the pages are already empty, and write performance is generally what you care about.

Note that the firmware in the SSD has to support TRIM, but the good news is that firmware updates are coming out for many SSDs to add TRIM support.

TRIM only improves performance when you delete files. If you are overwriting an existing file, TRIM doesn't help and you'll get the same write performance degradation as without TRIM.

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morean51
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interesting

thank you for sharing such interesting review

raoulsatar
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USB Flash Tools

USB Flash Tools at:

http://www.sdean12.org/USBFlashTools.htm

includes a special "Erase" function specially designed for flash drives, adn overwrites everything so it can't be retrieved

John T. Haller
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Exactly The Same

This tool just does exactly the same thing as Eraser Portable does, nothing more.

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ottosykora
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it works under windows

or what ever current OS, therefore it will write, overwrite and so on only on items on the virtual file system (e.g. windows readable file system) and will not access the flash file system directly at all. So sorry, such app is same value as any other writing to the flash under windows, no matter what 'special' code or pattern it does write to it.

Otto Sykora
Basel, Switzerland

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