RE: Interesting One

["Dan Darden" <dld2517 () yahoo com>]

John,

Think atomically.  There can be millions of atoms in a apace the size of a
pin tip.  A write head need not turn every atom in a layer of magnetic
material one way or the other.  It only needs to turn just enough 'clearly'
one way in order for the read head to pick it up again.  If we talk about a
layer of magnetic material that is just .0001" thick we are still talking
about layers upon layers upon layers (need I go on....) of atomic material.

It can be done!


Dan Darden.

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-----Original Message-----
From: John Orr [mailto:JOrr () austinbank com]
Sent: Tuesday, October 29, 2002 12:15 PM
To: dadams () johncrowley co uk; security-basics () security-focus com
Subject: Re: Interesting One


  Personally, I think he is full of... hot air.

  Bits are either "on" or "off", "1" or "0".  If you change that pattern
(i.e. write over the same data area with a different sequence of bits), then
the previous state of that field would not be determinable.  Granted, there
may be some residual magnetic field left on a particular area that is now
"0" that had been "1", but the converse would not be true.  There would be
no residual field to read on an area that is now "1" that had been "0".

  Sounds like sales fluff to me.

  Anyway, that is my opinion, based on years of experience and a good
knowledge of physics.

-John

--------------------------------------
John Orr
VP/CIO
Austin Bank
903.759.3828 x2113
903.297.3094 fax
jorr () austinbank com

> > > "Dave Adams" <dadams () johncrowley co uk> 10/28/02 04:06PM >>>
Greetings Folks,

I had an interesting conversation today with someone from FAST
(Federation
Against Software Theft) They pretend not to be a snitch wing of the BSA.
Anyway, to get to the point, the guy that came to see me said that their
forensics guys could read data off a hard drive that had been written
over
up to thirty times. I find this very hard to believe and told him I
thought
he was mistaken but the guy was adamant that it could be done. My
question
is, does anyone have any views on this, or, can anyone point me to a
source
of information where I can get the facts on exactly how much data can be
retrieved off a hard drive and under what conditions etc etc.

Thanks

Dave Adams



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