Comments for Do I need a file shredder for my USB Flash Drive?

Comment from Rasty on 2009-09-29

2009-09-29T20:44:26Z

Just saying no over and over again doesn't make it so.

I think only a designer of the flash drive wear-leveling system (WLS) can answer the question with assurance.

If a file is handed over to the WLS by the OS to be stored, the WLS would have to have a way to retrieve the bits and hand it back to the OS. This implies some kind of directory. Unless you can be assured that this low level directory entry is not accessible after the file is erased, then the file could presumably be recovered by specialized software.

When you say that a file only needs to be overwritten once on a flash drive, it leads me to believe that you don't know what you are talking about. If the file is distributed in a random fashion by the WLS, you would not have to erase it even once, rather you would only have to erase the directory entry to make in inaccessible, since there is no contiguous data. Without the directory entry, there would be no way to re-assemble the file.

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Comment from steve schwartz on 2009-05-15

2009-05-16T00:17:15Z

Here is the answer. The hardware leveling software is integrated with the filesystem in ways that are not obvious. This has to be the case because the card cannot produce memory from nothing. In other words if you "erase" file A which say is a large file of 1Gb from nowhere. It takes it from the free space of the filesystem. It tracks how many times each block is used.

Can the user who posted the original question attempt to erase all unused space on the filesystem once, I think this would get it.

Steve

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Comment from Martin Müller on 2009-04-15

2009-04-15T10:28:00Z

Hello,

does "Wear levelling" consider about partititions?

Example: 4 GB USB Stick with two partititions

1. Linux Ext2 - 8MB
2. Windows FAT - Rest of it

If I overwrite partitition 1. once with random data, will there be left data from that partitition somewhere on the stick because of "Wear levelling"?

Wear leveling is not externally visible, period. So while it might be happening under the hood across all bits stored on the device, you would not see it.

- Leo
15-Apr-2009

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Comment from Chris on 2009-03-22

2009-03-23T00:34:53Z

As someone with a scienctific background it would be easier to recover data from from many passes than from a few and here's why...

Granted the signal of the original files will become weaker the more passes one does, and more difficult to recover, but in essence the file would be less corrupt. The more random passes one does the more the scrambled signal evens out. Everyone should know this from statistics, flip enough heads and tails and you'll get a 50/50 split. It's kind of like cryptography in a way if you visualize each track as a column, but I digress, similarily if you only do a few passes the original signal will be stronger but more corrupt. hd only though not sure about flash.

Um...no. The more you overwrite it with random data the more difficult it will be to recover. (And overwriting ONCE is all you need for flash).

- Leo
23-Mar-2009

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Comment from MikeJC in Maine on 2009-03-19

2009-03-19T13:08:03Z

What about other forms of flash memory? Like SD cards and their ilk. Do they wear out as well?

Yep. Flash memory is much flash memory. There are differences in quality, of course.

- Leo
19-Mar-2009

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Comment from Nicholas Gimbrone on 2009-03-14

2009-03-14T21:33:48Z

Wear leveling would increase the chances of recovery if the recovery program is looking at ALL of the free blocks... as there is still a block on that USB that contains that data.

Again, no. Wear leveling does not increase the chances of recovery.

- Leo
15-Mar-2009

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Comment from t on 2009-03-14

2009-03-14T07:03:37Z

Wear leveling means it is writing the shred to other parts of the memory drive, thus it does not overwrite the original file remnants.

And, voila, the old file remains intact to a file recovery program.

contig is "complicated"??? sheesh.

It would be better to use a truecrypt volume to keep private stuff private on a flash disk. Perhaps the only way.

Wear leveling is implemented at the hardware level and is transparent to applications. If you overwrite byte "x" on the media, then it will always look like byte "x" was overwritten, even though is might reside elsewhere on physical media. Put another way, wear leveling does not increase the chances of file recovery because it's completely hidden.

- Leo
14-Mar-2009

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Comment from Gamar Damlani on 2009-03-13

2009-03-14T04:32:50Z

i want to view & recover my picture files but how can i recover picture files on my USB if i have already cut them from my USB and paste it on a folder who happens to be inffected by a virus giving it the cause why i cannot view my Picture files anymore.

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Comment from Rocco on 2009-03-11

2009-03-11T09:13:44Z

Wouldn't East-Tec Eraser be the best option for USB and disk?
http://www.east-tec.com/

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A comment on: Do I need a file shredder for my USB Flash Drive?

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Comment from hemraj on 2009-03-10

2009-03-10T19:46:00Z

it is very good when delete function not work

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A comment on: Do I need a file shredder for my USB Flash Drive?

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Comment from Mike in Pennsylvania on 2009-03-10

2009-03-10T15:59:30Z

SDelete is a little complicated for the casual user.

I use the freeware Eraser which gives you the option to write once with Pseudorandom Data. After installing the software, you can do a right click on the file name and select ERASE.

http://www.brothersoft.com/eraser-12113.html

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A comment on: Do I need a file shredder for my USB Flash Drive?

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Comment from Philip on 2009-03-08

2009-03-09T03:51:39Z

Modern flash drives force new data to locations that have not been used (as much) as current locations to keep wear as even as possible. I suspect that these newer flash drives divert the shredder to locations that don't include the data you're trying to shred. The data from the file you're trying to shred stays intact while some innocent area gets "shredded". ;-)

That's true, but it should never be visible in any useful way to a file recover program - or to any program for that matter. "Wear levelling" as it's called is all hidden within the hardware.

- Leo
09-Mar-2009

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A comment on: Do I need a file shredder for my USB Flash Drive?

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