Security and harddisk crubbing in Linux

[Matthew Hawkins]

On Fri, 26 Oct 2001, Anthony Wesley wrote:
> Why write random bits? Why not just zero everything with
> 
> 	... dd if=/dev/zero ...
> 
> This will run somewhat faster.

Sure, but the data can still be recovered.  Last time I read one of
those standards you had to do four passes; write zeros, write ones,
write alternating zeros and ones, then write random patterns.

Apparently there is the technology now to recover from 6 overwrites, so
maybe the standards have been upgraded accordingly.

(PS: by "ones" I mean all 8 bits in the byte turned on, not just the
number "1" - for the hopefully obvious reason ;)

-- 
Matt