In Message-ID:<Xns9A4DA577A884FYAsfKJXSTO@194.117.143.37>,
bealoid <signup@bealoid.co.uk> wrote:

>1) The theory is that you don't know what tech your attacker has, and you
>don't know what tech your attacker will invent in the future, and so you
>over-write many times with patterns and random data, then take the
>platters out and physically destroy them.

Pointing out the possibilities of future tech (and the
near-impossibility of ruling out what future tech might be) puts
overwriting into a different perspective. Thank you.

>2) You have sensitive information (patient medical stuff, for example)
>and it's just easier to do the belt-and-braces destroy thing than a
>sensible destroy, if only to keep the wing-nuts out of your hair. You've
>removed any doubt.

CYA is a very good reason, but not a technical one ;-).

>People might prefer to do cost-benefit risk analyses - it takes time (and
>thus money) to overwrite disks.

And, it takes even more time and money to do the analysis of
how much overwriting is necessary. Thus, we're likelier to get
"guidelines" than reasoned, technical answers.

So, even if today N overwrites makes a disk unreadable,
tomorrow someone might find a way to read it. (And, of course,
even N overwrites might be readable by a closed-mouthed government
agency.)

Short of a theoretical proof (which unlikely to have much to
do with real-world technology), N can be argued but might never be
enough for absolute security.

I think this explains the lack of reasons for the guidelines
currently available.

Thanks to all who responded to this thread. I responded to
this post because that's when the answers sunk in, but all of the
responses were helpful in bringing me to the state where I could
understand the gestalt.

--
Arthur T. - ar23hur "at" intergate "dot" com
Looking for a z/OS (IBM mainframe) systems programmer position