SUMMARY: Disk Sanitization

From: Gary Carr (
Date: Thu Apr 29 1999 - 10:02:11 CDT

Sorry about forgetting the "SUMMARY" in Subject, but I also have some new
information so I thought I'd send this again.

I recieved many replies to my original question on "sanitizing" disks. I
would like to thank everyone who took the trouble to reply, especially the
people whe went to the trouble to send programs or scripts.

My Original post was:
>I have just handed a mandate to "sanitize" all disk that are sent out for
>repair. The sanitization procedure consists of writing all zeros to every
>block of the disk, then all ones, then some other pattern followed by a
>reformat. This is apparently a well known procedure. Programs like Norton
>Utilities have a "Government Wipe" Option to do this procedure.
>Does anyone know of a Solaris or Unix program to do this for Sun disks?

The most common answer was that you can do this with the Solaris purge
option of the format command. Several people sent scripts using dd to write
to the disk. A couple of people sent C programs which they had used in the
past. I found one commercial program called UniShred. Info at

NEW -- Also "Almond Utilities", offers a UNIX version of Norton's Wipe Disk.
Didn't get a URL.

A number of people brought up the valid point that you can't write to a
disk that is unusable. The only way to really make sure no one can read
such a disk is to degauss it with a "honking big electromagnet". This is in
fact what our security people want us to do.

What we hope to do, since we are not doing any classified computing of any
kind, was to see if we could get our security people to accept a plan to
"sanitize" as much of a disk as was writable. If the disk could not be
written, then it didn't need sanitization, at least at this level. I know,
good luck ;-) We'll give it a shot. If we can't get approval, then back to
the "honking big electromagnet".

NEW -- Another item I discovered after talking to our Sun Maintenance contract
representative is that Sun offers a "Secure Disk" upgrade to thier standard
contracts. If you purchase the upgrade, when they replace a bad disk you can
keep the old disk and dispose of it however you choose (degauss, etc). The cost
is based on the number of workstations, servers, and "external" disks that you
have. It is fairly expensive if you have a good sized facility, it looked to me
like it might be cheaper to buy your own spares.

NEW -- Also a comment that acceptable means of sanitization are explosives,
thermite, use belt grinder to remove magnet media from platters (is this a disk
grinder:-), etc.

Again, many thanks to the people who replied.

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