Removing data in a secure manner?

[Rick Deckard]

I was just wondering what would be a good way to completely remove data from a hard disk in OpenBSD? Somehow using dd with /dev/random to the disk device? Three times in a row?

Sorry for being a Noob but I'm still trying to learn Unix.
Yahoo! Mail Plus - Powerful. Affordable. Sign up now

[Theo de Raadt]

Post by Rick Deckard
I was just wondering what would be a good way to completely remove
data from a hard disk in OpenBSD? Somehow using dd with /dev/random
to the disk device? Three times in a row?

Any metal working shop will be able to help you.

[Rick Deckard]

I just got back from my local metal working shop, and they said they don't support OpenBSD since they use Linux. They helped me resolve my issue. Thanks for directing me to the people who would help.

data from a hard disk in OpenBSD? Somehow using dd with /dev/random
to the disk device? Three times in a row?

Any metal working shop will be able to help you.
Yahoo! Mail Plus - Powerful. Affordable. Sign up now

[Joseph W. Shaw II]

Post by Rick Deckard
I was just wondering what would be a good way to completely remove data
from a hard disk in OpenBSD? Somehow using dd with /dev/random to the
disk device? Three times in a row?
Sorry for being a Noob but I'm still trying to learn Unix.

If the data is not encrypted, the only real way to securely delete it is
physical destruction. My personal preferred method is a magazine full of
5.56 NATO in my ar-15 at 50 yards. A .50BMG would certainly do it in one
shot. If you have the means available, and it's not illegal where you
live, it can be quite fun.

Of course, if you're not worried about someone going all out with an MRI
to retreive the data on the drive, a standard magentic media bulk eraser
should work. The only caveat is that it will certainly fry the drive
heads in the process.

--
Joseph

[Ralph Kube]

Post by Joseph W. Shaw II

Post by Rick Deckard
I was just wondering what would be a good way to completely remove data
from a hard disk in OpenBSD? Somehow using dd with /dev/random to the
disk device? Three times in a row?
Sorry for being a Noob but I'm still trying to learn Unix.

If the data is not encrypted, the only real way to securely delete it is
physical destruction.

Thats what I think too. There was an article on slashdot recently which
was about the data findings on used hdds. Even if you overwrite your
data several times with different values (on the binary level), there
are still chances that you can tell the state of the magnetic field how
it was before.
The thing is, that this is very expensive. I would guess that the
chances of rebuilding the original data after overwriting it several
times is very low.

Ralph

[Rick Deckard]

I think I'm going to go with the melting idea. Thanks very much for the advice everyone. ;-)

Post by Rick Deckard
I was just wondering what would be a good way to completely remove data
from a hard disk in OpenBSD? Somehow using dd with /dev/random to the
disk device? Three times in a row?
Sorry for being a Noob but I'm still trying to learn Unix.

If the data is not encrypted, the only real way to securely delete it is
physical destruction. My personal preferred method is a magazine full of
5.56 NATO in my ar-15 at 50 yards. A .50BMG would certainly do it in one
shot. If you have the means available, and it's not illegal where you
live, it can be quite fun.

Of course, if you're not worried about someone going all out with an MRI
to retreive the data on the drive, a standard magentic media bulk eraser
should work. The only caveat is that it will certainly fry the drive
heads in the process.

--
Joseph
Yahoo! Mail Plus - Powerful. Affordable. Sign up now

[Gordon Grieder]

Post by Joseph W. Shaw II
Of course, if you're not worried about someone going all out with an MRI
to retreive the data on the drive, a standard magentic media bulk eraser
should work. The only caveat is that it will certainly fry the drive
heads in the process.

I apologize for this being off topic, but...

We use MRIs at work (up to 11T), I'd think that they would just erase the
data :) As an aside, a cleaner at work accidently brought a shopvac into
one of the MRI rooms. Oops. The vacuum *took off* through the air and stuck
to the MRI. It took several people with cargo nets to get it off.

See a pic at Loading Image...

[Morten Liebach]

Post by Rick Deckard
I was just wondering what would be a good way to completely remove
data from a hard disk in OpenBSD? Somehow using dd with /dev/random
to the disk device? Three times in a row?

Mark Grimes used to have a patch for OpenBSD 3.2 that added an '-s'
option that would perform secure deletion. The file is named
rm_gutmann-3.2.diff, you might find it with google, since Mark has
pulled it from his website at http://www.packetninja.net/.

But again, melting a disk is better.

Have a nice day
Morten

[j***@hcpnet.org]

I had the very same problem, and if you would like to reuse the hard
drive, or sell it, and not destroy it, you can try out this program I
wrote, that will COMPLETELY erase the data on the drive. It polarizes the
disk which causes all the bits to be zero'd then one'd (0x00 then 0xff)
then writes a random character to the disk (in the case of my program,
0xf6) and this will erase all data securely. In fact, this is how the
United States government removes Secret classified data from hard drives,
I just wrote a free program, licensed under BSD, to do it.

URL: http://www.sourceforge.net/projects/disc-wipe/

Jason

[Joseph W. Shaw II]

Post by j***@hcpnet.org
I had the very same problem, and if you would like to reuse the hard
drive, or sell it, and not destroy it, you can try out this program I
wrote, that will COMPLETELY erase the data on the drive. It polarizes the
disk which causes all the bits to be zero'd then one'd (0x00 then 0xff)
then writes a random character to the disk (in the case of my program,
0xf6) and this will erase all data securely. In fact, this is how the
United States government removes Secret classified data from hard drives,
I just wrote a free program, licensed under BSD, to do it.

With all due respect, that is most certainly not how the US government
removes secret classified data from magnetic media. First, let me forward
you to a link from this mailing list we had last year discussing the
topic:

http://www.sigmasoft.com/cgi-bin/wilma_hiliter/openbsd-misc/200211/msg01399.html

I'll reiterate from my previous posting that modern hard drive write
heads are unable to put the magnetic media back in a median state,
therefore software methods of removing data are less than foolproof. An
audit of the DoD by the Inspector General found that it was indeed
possible to recover sensitive data from drives that had been certified as
being wiped. That's why in all cases the current operating procedure of
the DoD is to destroy all hard drives from all systems, regardless of the
classification of the data on them.

And to reinforce that, take a look at this letter sent out in 2001 by
Deputy Secretary of Defense Rudy de Leon about the ability to recover
sensitive data off of magnetic media believed to be "sanitized."

http://www.c3i.osd.mil/org/cio/doc/computerdisposal.doc

Granted, as it has already been mentioned by others, it begs the question
of how important the information is you're trying to get rid of, who might
want the information, and how far they are willing to go to get it?

Have you tried your program against any of the available free and
commercial forensics programs out there to verify your claims? The
software that was previously considered acceptable by DoD standards used
the same scheme as you claim.

Regards,
--
Joseph

[j***@hcpnet.org]

I had someone from NSA tell me how they removed secret classified data
(data classified higher than that was degaused) and I had a forensics guy
tell me the most secure way to delete data from a drive, while still being
able to use it. He said, using the method I used in my program, that some
data bits would be recoverable, however, no full bytes, and he is
currently testing it now. Please feel free to test my program, use it
however you want, and please give me feedback on whether it worked at all
for you, what you did with it, etc... I would be very interested to get
the opinion from as many people as possible

Post by j***@hcpnet.org
I had the very same problem, and if you would like to reuse the hard
drive, or sell it, and not destroy it, you can try out this program I
wrote, that will COMPLETELY erase the data on the drive. It polarizes the
disk which causes all the bits to be zero'd then one'd (0x00 then 0xff)
then writes a random character to the disk (in the case of my program,
0xf6) and this will erase all data securely. In fact, this is how the
United States government removes Secret classified data from hard drives,
I just wrote a free program, licensed under BSD, to do it.

With all due respect, that is most certainly not how the US government
removes secret classified data from magnetic media. First, let me forward
you to a link from this mailing list we had last year discussing the
topic:

http://www.sigmasoft.com/cgi-bin/wilma_hiliter/openbsd-misc/200211/msg01399.html

I'll reiterate from my previous posting that modern hard drive write
heads are unable to put the magnetic media back in a median state,
therefore software methods of removing data are less than foolproof. An
audit of the DoD by the Inspector General found that it was indeed
possible to recover sensitive data from drives that had been certified as
being wiped. That's why in all cases the current operating procedure of
the DoD is to destroy all hard drives from all systems, regardless of the
classification of the data on them.

And to reinforce that, take a look at this letter sent out in 2001 by
Deputy Secretary of Defense Rudy de Leon about the ability to recover
sensitive data off of magnetic media believed to be "sanitized."

http://www.c3i.osd.mil/org/cio/doc/computerdisposal.doc

Granted, as it has already been mentioned by others, it begs the question
of how important the information is you're trying to get rid of, who might
want the information, and how far they are willing to go to get it?

Have you tried your program against any of the available free and
commercial forensics programs out there to verify your claims? The
software that was previously considered acceptable by DoD standards used
the same scheme as you claim.

Regards,
--
Joseph

[David Norman]

Post by j***@hcpnet.org
I had someone from NSA tell me how they removed secret classified data
(data classified higher than that was degaused) and I had a forensics guy
tell me the most secure way to delete data from a drive, while still being
able to use it. He said, using the method I used in my program, that some
data bits would be recoverable, however, no full bytes, and he is
currently testing it now. Please feel free to test my program, use it
however you want, and please give me feedback on whether it worked at all
for you, what you did with it, etc... I would be very interested to get
the opinion from as many people as possible

People time and time again on this list say if you want to destroy
data, destroy the hard drive. That sounds like everyone who wants to
destroy data also happens to be able to buy a replacement drive. It
still doesn't provide an answer to the question of how to get data off
a drive. As their FAQs will say, these links are "good enough for most
people".

http://dban.sourceforge.net/
http://www.heidi.ie/eraser/


dumb yahoo tag follows
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com

[Tim Donahue]

Sorry for not responding earlier work seems to get in the way sometimes.
When I say 'destroy the drive' I am talking about a situation where the
drive is going to be disposed of. If the drive is going to be reused in
my company, then for most cases just zeroing the drive is sufficient.
If there is data that I don't want to take any chances of it being
recovered (and is still going to be reused), then I'll overwrite the
drive with the 3 pass method.

Tim Donahue

-----Original Message-----
Sent: Wednesday, February 05, 2003 11:55 PM
Subject: Re: Removing data in a secure manner?

Post by j***@hcpnet.org
I had someone from NSA tell me how they removed secret

classified data

Post by j***@hcpnet.org
(data classified higher than that was degaused) and I had a

forensics

Post by j***@hcpnet.org
guy
tell me the most secure way to delete data from a drive, while still
being
able to use it. He said, using the method I used in my program, that
some
data bits would be recoverable, however, no full bytes, and he is
currently testing it now. Please feel free to test my

program, use it

Post by j***@hcpnet.org
however you want, and please give me feedback on whether it

worked at

Post by j***@hcpnet.org
all
for you, what you did with it, etc... I would be very interested to
get
the opinion from as many people as possible

People time and time again on this list say if you want to
destroy data, destroy the hard drive. That sounds like
everyone who wants to destroy data also happens to be able to
buy a replacement drive. It still doesn't provide an answer
to the question of how to get data off a drive. As their FAQs
will say, these links are "good enough for most people".

http://dban.sourceforge.net/
http://www.heidi.ie/eraser/


dumb yahoo tag follows
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com

[Chuck Yerkes]

Post by Tim Donahue
Sorry for not responding earlier work seems to get in the way sometimes.
When I say 'destroy the drive' I am talking about a situation where the
drive is going to be disposed of. If the drive is going to be reused in
my company, then for most cases just zeroing the drive is sufficient.
If there is data that I don't want to take any chances of it being
recovered (and is still going to be reused), then I'll overwrite the
drive with the 3 pass method.

And ask what the data is really worth? Is someone going to pull
platters and spend a couple thousand to get the data? Or you are
you worried about someone getting intact disks?
Or are you worried about the bosses cousin being given the disks
and you don't want them to see the data?


I've taken a drill press with a 1/4" bit and punched to holes in a
disk. Unlikely that someone wanted our data in the first place,
this kept a dumpster rescue from being likely. Were they really
determined, yeah, they could have see cost spreadsheets for 2 year
old film and commercial shoots. Stuff *we* didn't care about.

Or go by a nice 20 oz straight claw hammer and whack the hell out
of the drive. Drill a hole, fill with sand.

It's likely that nobody cares about the data that much.

You have tot decide and you need to have policy and OpenBSD lists
aren't the place for that.

[tim smith]

sorry for reviving an old topic but i just have a quick question, most seem
to be of the opinion that data can be recoverd as long as the disk isn't
ashes, does anyone know of any articles or faq's on how data is recoverd
from dead disks? i'd be intrested in reading them. sorry if it's a bit off
topic, but your all so smart and likely to know this stuff ( shameless
flattery )
cheers
Tim Smith

[Damien Miller]

Post by tim smith
sorry for reviving an old topic but i just have a quick question, most seem
to be of the opinion that data can be recoverd as long as the disk isn't
ashes, does anyone know of any articles or faq's on how data is recoverd
from dead disks? i'd be intrested in reading them. sorry if it's a bit off
topic, but your all so smart and likely to know this stuff ( shameless
flattery )
cheers
Tim Smith

I don't know if it covers recovery techniques, but Peter Guttman's paper
covers storage encodings and how they relate to deletion strategies:


http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

[Ron Rosson]

--On Wednesday, February 19, 2003 11:31:12 +1100 Damien Miller

Post by Damien Miller

Post by tim smith
sorry for reviving an old topic but i just have a quick question, most
seem to be of the opinion that data can be recoverd as long as the disk
isn't ashes, does anyone know of any articles or faq's on how data is
recoverd from dead disks? i'd be intrested in reading them. sorry if
it's a bit off topic, but your all so smart and likely to know this
stuff ( shameless flattery )
cheers
Tim Smith

I don't know if it covers recovery techniques, but Peter Guttman's paper
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

I have a patch written by Mark Grimes that adds this functionality to rm. I
use it when I have to.. It is not speedy but does work.

-Ron

--
----------------------------------------------------------------------------
Ron Rosson ... and a UNIX user said ...
The InSaNe One rm -fr *
***@oneinsane.net and all was /dev/null and void()
----------------------------------------------------------------------------

[Scott Francis]

Post by tim smith
sorry for reviving an old topic but i just have a quick question, most seem
to be of the opinion that data can be recoverd as long as the disk isn't
ashes, does anyone know of any articles or faq's on how data is recoverd
from dead disks? i'd be intrested in reading them. sorry if it's a bit off
topic, but your all so smart and likely to know this stuff ( shameless
flattery )
cheers
Tim Smith

I have not personally done much in the way of forensics of this type, but you
should probably check out The Coroner's Toolkit, and read the background info
on that same site.
http://www.porcupine.org/forensics/tct.html

--
--
Scott Francis || darkuncle (at) darkuncle (dot) net
illum oportet crescere me autem minui

[demime 0.98d removed an attachment of type application/pgp-signature]

[Tim Donahue]

A commercial recovery service: http://www.drivesavers.com/

I haven't seen any good links on the recovery of data, but this is a
couple cool picutres and a bunch of links that might be of interest:
http://www.spmtips.com/app/Subjects/datastorage.htm

Tim Donahue

-----Original Message-----
From: Scott Francis [mailto:***@darkuncle.net]
Sent: Tuesday, February 18, 2003 10:19 PM
To: tim smith
Cc: ***@openbsd.org
Subject: Re: Removing data in a secure manner?

Post by tim smith
sorry for reviving an old topic but i just have a quick question, most
seem to be of the opinion that data can be recoverd as long as the
disk isn't ashes, does anyone know of any articles or faq's on how
data is recoverd from dead disks? i'd be intrested in reading them.
sorry if it's a bit off topic, but your all so smart and likely to
know this stuff ( shameless flattery ) cheers
Tim Smith

I have not personally done much in the way of forensics of this type,
but you should probably check out The Coroner's Toolkit, and read the
background info on that same site.
http://www.porcupine.org/forensics/tct.html

--
--
Scott Francis || darkuncle (at) darkuncle (dot) net
illum oportet crescere me autem minui

[demime 0.98d removed an attachment of type application/pgp-signature]