[ubuntu-uk] Securely delete data

[Alan Pope]

On 18/11/12 10:16, Tyler J. Wagner wrote:
> On 2012-11-16 17:30, Alan Pope wrote:
>> More passes don't really give you any benefit. A simple single run of dd
>> is sufficient.
>
> That depends against what you are trying to defend. It is possible, with
> specialist tools, to recover data after a single wipe.

People say that a lot. Prove it.

  This is especially
> true when the wipe is done with uniform data, such as all zeros. So if you
> want to prevent the next owner of a laptop from running photorec, one pass
> is fine. If you want to stop a data recovery specialist or intelligence
> agency, it is not.
>

A while back someone tested this theory which is well distributed by 
technical people. He put a known string in a file on a disk, then dd'ed 
zeores over it and called file recovery companies to challenge them to 
get it back. As soon as he mentioned he'd done a single pass of dd'ing 
zeroes over it _none_ of them would accept the challenge.

One professional data recovery company replied with:-

"According to our Unix team, there is less than a zero percent chance of 
data recovery after that dd command. The drive itself has been 
overwritten in a very fundamental manner. However, if for legal reasons 
you need to demonstrate that an effort is being made to recover some or 
all of the data, go ahead and send it in and we'll certainly make an 
effort, but again, from what you've told us, our engineers are certain 
that we cannot recover data from the drive. We'll email you a quote."

Cheers,
-- 
Alan Pope
Engineering Manager

Canonical - Product Strategy
+44 (0) 7973 620 164
alan.pope at canonical.com
http://ubuntu.com/