[Gllug] Disk Wipe

[Alain Williams]

On Mon, May 24, 2004 at 12:01:35PM +0100, FORSTER, David wrote:
> Hi,
> 
> I'm sure this has come up before and it's probably quite a common thing, but
> my googling is obviously not up to scratch this morning!! Can one of you
> kind folks help?
> 
> I want to perform a secure wipe of a disk. You know the type of thing where
> you overwrite the data on the disk with (pseudo)random bytes before marking
> it as deleted in the FAT (or equivalent). The disk in question has a single
> formatted partition (not sure if it's FAT32 or NTFS) and I want to erase all
> the data securely, I don't care if I lose the partition table or not because
> it will be repartitioned etc. anyway.
> 
> Ideally I would like to be able to use a Knoppix CD to do this, and if
> anyone can suggest a method that I can use which will either wipe individual
> files OR whole disks then that would be the icing on the cake :o)

How secure do you want to be ? Or how sensitive is the data on the disk ?

If it is to be proof against the average guy in the street or you are protecting
non sensitive personal letters/..., then simply copying /dev/zero to the disk
will be enough:
	dd if=/dev/zero of=/dev/hda

If you are really worried (lives depend on it or you need to keep the CIA/MI5 out)
the only real solution is a large hammer followed by an acid bath. The point is
that write once and you can still 'see' the shadow of what was there before
(OK you need special kit), this shadow will go if you write lots of time but
you will be left with data written slightly off track when the drive was a
bit hotter/colder. Also if a track becomes defective a modern drive will mark it
as dud and substitute a spare track - invisibly to the operating system.

I suspect that a simple 'dd' will be enough for most of us.

-- 
Alain Williams

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