data shredder

[Gilles Gravier]

Hi!

On 21/12/2009 09:55, Amedee Van Gasse (ub) wrote:
> On Mon, December 21, 2009 04:28, jesse stephen wrote:
>   
>> I'm looking for a data shredder for ubuntu 9.10
>>     
> The other suggestions are good, and if you want a low-tech solution:
>
> 1) delete your files with rm as usual
> 2) overwrite the empty disk space with zeroes or random data
> Use either one of these commands:
>
> dd if=/dev/null of=nullfile bs=1M
> dd if=/dev/random of=randomfile bs=1M
>
> They will create a file called 'nullfile' or 'randomfile', filling all the
> empty space on your disk. The dd command will automatically abort when all
> free disk space is used.
> Please note that this can take a *long* time, depending on the size of
> your free disk space. Also /dev/random is a special device that generates
> "entropy" (=random data) and with this method you use up all the available
> entropy so sometimes it will stall until it has created enough new
> entropy.
>
> When it's done, rm nullfile or em randomfile.
> If you're really paranoid, repeat the procedure a couple of times.
>
>
>   
The problem with these commands, is that you're not really helping...
Forensics tools will read below one or more levels of re-write. You need
to do this several times in a row... and, more importantly, you need to
use special data patterns that will actually make reading shadows of
former data harder if not impossible. There are standards for that. And
they do not involve writing random data or zeros, but actual specific
patterns.

Gilles.