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RE: Erasing a hard disk easily
From: "Peter B. Harvey (Information Security)" <peterharvey () emergency qld gov au>
Date: Tue, 13 Jul 2004 09:59:01 +1000


Standard data recovery tools will be stopped by writing zeros to the disk. This includes programs such as OnTrack Data 
Recovery Pro.

However i have been informed that equipment exists to retrieve data that programs on a normal system cannot. Hence the 
writing multiple times with all 0 then all 1 then all 0 will cycle the disk so that it is virtually impossible to 
determine the residual data (please note all 1 means all bits are 1).

My two bits

Peter

-----Original Message-----
From: Gregh [mailto:chows () ozemail com au]
Sent: Tuesday, July 13, 2004 8:20 AM
To: full-disclosure () lists netsys com
Subject: Re: [Full-disclosure] Erasing a hard disk easily



----- Original Message -----
From: "Maarten" <fulldisc () ultratux org>
To: <full-disclosure () lists netsys com>
Sent: Tuesday, July 13, 2004 7:23 AM
Subject: Re: [Full-disclosure] Erasing a hard disk easily



An overwrite with all zeros will -allegedly- not withstand a serious
data-recovery attempt by professionals, not even when repeated.

I know you stated "allegedly" but this subject interests me. Many years ago,
a good friend of mine who had been in to pirating and suddenly realised he
could end up behind bars if he was ever caught got the shakes thinking about
it. He deleted it all and I let him know that wasn't good enough. He got
hold of a simple basic program that kept looping until the disk was full,
writing a line of 80 of the number "8" to the disk making one file that got
bigger and bigger until, ultimately, it filled the disk. Once filled, it
would close the file and all you had to do was boot into DOS and delete it
and the space was free once more all overwritten with the number "8"
wherever you looked with a sector editor.

Since that time I have seen sensationalist TV shows showing how FBI and CIA
operatives get stuff out written to a sector BEFORE the sector was
overwritten and I honestly cannot understand how that could be, if at all
possible. Am I right in thinking those shows are bull?

Greg.

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