The Great Zero Challenge

[Mark Sowerby]

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