The Great Zero Challenge

[Dan Beale-Cocks]

The ATA command set includes a SECURE ERASE function, which IIRC does 
overwrite sectors marked as bad.  It's a bit quicker than DBAN.

I'm not aware of any commercial company, anywhere in the world, who 
claims to be able to recover any data from a disk that's been 
overwritten, even just once with all zeros.



Mark Sowerby wrote:
> Hi,
>
> It goes withouth saying, but I will state it for completeness as I 
> don't think it has been stated in the thread (apologies, suck eggs 
> etc) - overwriting is different from deleting, which generally does 
> not delete.
>
> Drives use pre-emptive error correction where they remap data from 
> weak sectors to spare sectors. So, whilst dd may actually oblitorate 
> the data (beyond economical physical recovery), it is unlikely that dd 
> will have erased all of the data as drive electronics (keeping the 
> weak sectors from being addressed by the computer) and mybe the 
> operating system device driver may have got in the way....It may be 
> the case that it is undesirable for even these mere remnants of data 
> trapped on the "weak" remapped sectors of the drive to be recovered.
>
> For HMG use only wiping systems listed at the link below should be 
> used, which have been tested to be suitable:
>
> http://www.cesg.gov.uk/site/iacs/itsec/
>
>
> With software based data erasure - if the method is not assured - then 
> you cannnot rely upon it to give assurance. However - it may be a case 
> that a complete overwrite (for example dd) is a suitable risk 
> mitigation method when taking into account what was actually on the 
> disk. There are plenty of Linux distributions that can be run from CD 
> that could be used to "dd" a drive. If there is no need to reuse a 
> drive, I find a large hammer works for me.
>
> BR
> Mark
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