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[Gaffers]

Recently on a course I was told that currently it was not possible to perform a permanent deletion of files held on  a USB/Flash drive which had something to do with the technology.  There are some products which claim to be able to but I am unsure as to the truth.   :-/ :-/

Maybe one of our resident techie experts can help 

[Jimbob]

if not, there are programs out there that will corrupt a file, ie overwrite with 1's, then 0's, then delete, so even if recovered, it is not the file that was wanted.

[Gaffers]

Thats what I thought, ie pretty much what a shredder would do but they seemed adamant about it  :-/

[Kevin Wood]

I believe the internal logic in a flash card will not overwrite sectors until it has to, in order to distribute the "wear" over the whole disk.

Probably your best bet is to get a file or files that will fill the disk, empty the disk and copy said files onto it, guaranteeing most of the sectors have been re-used.

Or get sammy out...

Or put it in a safe place. It'll fail sooner rather than later and your data will be quite safe.

Kevin

[Gaffers]

I believe the internal logic in a flash card will not overwrite sectors until it has to, in order to distribute the "wear" over the whole disk.

Probably your best bet is to get a file or files that will fill the disk, empty the disk and copy said files onto it, guaranteeing most of the sectors have been re-used.

Or get sammy out...

Or put it in a safe place. It'll fail sooner rather than later and your data will be quite safe.

Kevin

But surely then if you know where the sectors used for a specific file are (if you dont then how do you read the file?) surely you know which sectors to erase?  Unless its something to do with media states and even when you have flipped the bits you can still recover the last value?  :-/

[cem_devecioglu]

as said above permanent deletion is only possible with filling the same area with another file..

but if you just delete it , as usual only the file header pointers will be deleted on the file allocation table..

[Kevin Wood]

I believe the internal logic in a flash card will not overwrite sectors until it has to, in order to distribute the "wear" over the whole disk.

Probably your best bet is to get a file or files that will fill the disk, empty the disk and copy said files onto it, guaranteeing most of the sectors have been re-used.

Or get sammy out...

Or put it in a safe place. It'll fail sooner rather than later and your data will be quite safe.

Kevin

But surely then if you know where the sectors used for a specific file are (if you dont then how do you read the file?) surely you know which sectors to erase?  Unless its something to do with media states and even when you have flipped the bits you can still recover the last value?  :-/

What I am saying is that overwriting the file with other data will cause unused sectors to be written to, in preference to existing sectors already allocated to that file to be written a second time. There are tools available to recover files from memory cards which simply sort through the unused sectors and chain them back into files.

Hence, you need to ensure they are overwritten by filling the device up with data.

Kevin