16 replies to this topic

[eknirb]

Secure File Deletion

DOD
NSA
Guttman


What is the difference between these?

[Augeas]

It's all explained when you select one or the other. DOD overwrites data 3 time with 'random' data, NSA with 7, and Guttman with 35. A simple overwrite, once with zeroes, is all you need to securely delete data, the rest are just wasting time, energy and your hard drive.

[YoKenny]

Welcome eknirb

Please read:
http://forum.pirifor...showtopic=20057

[cl5776]

Augeas, on Jan 24 2009, 09:30 AM, said:

A simple overwrite, once with zeroes, is all you need to securely delete data, the rest are just wasting time, energy and your hard drive.

Good day. I have been a faithful user of CCleaner for a long time. I feel it is one of the best cleaning products on the market. However, seeing this thread...and the one referenced in the prior post...concerns me. I have to admit, I was under the impression that the more times the application wipes, the better the data will be erased. Therefore, I have been using the Guttman 35 pass option religiously.

This latest time that I used the application, the process is well into its 6th hour. Yes, that was not a typo. I started the process just before 24 came on at 9pm EST and it is now almost 3:30am EST now. A normal scan for me is about 30 minutes to one hour or so, using the Guttman secure file deletion option. Granted, over the last couple of weeks, I have been doing some heavy music downloading. The last scan I ran a few days ago freed up over 8GBs of space. I expected this scan to be about an hour or so and free up as much if not more hard drive space.

I figured I would come to the vendor's site to see if there was anything abnormally wrong with this situation. It comes as a big surprise to realize that doing any more than the normal file deletion is a waste of time. My question is this: If anything more than the normal file deletion is a waste of time, energy, and resources, why is secured file deletion (DOD, NSA, or Guttman) offered as an option?

Thanks

[login123]

Hi cl5776 and eknirb.

There are lots of Googleable (is that a word?) articles about secure deletion. Not going to repeat them here, but in short, how much energy you put into deleting depends what you want to do.

- If you just want to delete files so that the space is freed up on the hard drive, just delete'em.
- If you want to prevent casual, easy recovery of something private, like say, an invitation to a surprise birthday party, then 1 overwrite will do it. The file name might still be there, but the file is now full of junk.
- If you want to prevent recovery of something really confidential, one of the standard schemes (DOD, NSA, etc) is generally regarded as better. For instance, if a computer used in a business is being transferred to a different user.
- If you want to prevent the super snoopers from ever seeing the file, replace the hard drive.

Edit: Feel like I should say more, am conflicting slightly with YoKenny. If I were responsible for protecting really important data, such as account numbers and personal ID numbers, I would replace the HD. No matter what the experts say publicly.

Not sure if Ccleaner overwrites the file tips or flushes the buffers when overwriting, or renames the files, but it is a very good deleter. Considering the other functions it can perform, it is a top notch app.

Just my opinion. Wait for some of the other members to post, most know more than I.
Hope this helps.

[Augeas]

I can only assume that either the developers are unaware of data coding techniques and modern HDD technology or (more likely) that they offer these options to stop sales/use being lost to competitors, as users see them as more sophisticated offerings. Customer demand, in other words.

Gutmann worked on Winchester disk technology from the early 1990's, and he had the grace to acknowledge in his 1996 paper that later disks, which everyone outside of a musuem is now using, use different coding techniques that make his overwriting patterns irrelevant. He said that 'A good scrubbing with random data will do about as well as can be expected.' But nobody reads that part of his paper. I doubt whether many people have read any part of his paper.

In any event, how many users need super-secure deletion? Where are the armies of electron-scanning microsopes?

I think that the Gutmann myth is so entrenched that it will not disappear voluntarily. The only way to remove it is for software vendors to stop including it as part of their products.

[cl5776]

Hi Augeas and login123. Thank you for the explanations. I just wanted to follow-up. The scan finally completed. It took 8 and a half hours but I recovered over 20GBs of space. I think you may have an idea as to what I am about to state next. Even though I now know that the Gutmann option is relatively pointless, I would be hard pressed to change at this point. I have been using Gutmann for so long that anything "lower" may seen inadequate. I may reduce down to NSA, though.

Thanks for your time.

[Augeas]

It is pointless. Gutmann coding does not apply to PRML coding, which all modern drives use. Good old Gutmann said his coding method was pointless. Think how many hours of you life you could be doing something really satisfying instead of watching a boring pc grind away. Think how many hours of our lives you could spare!

[YoKenny]

Augeas, on Jan 27 2009, 05:56 AM, said:

I think that the Gutmann myth is so entrenched that it will not disappear voluntarily. The only way to remove it is for software vendors to stop including it as part of their products.

I have been saying that about CCleaner ever since Secure Deletion offered more than Simple Overwrite (1 pass)

[Marko897]

you just red my mind

Edited by Andavari, 16 April 2010 - 11:21 PM.
And your spam link has gotten you banned.

[marmite]

Augeas, on Jan 27 2009, 11:56 AM, said:

I can only assume that either the developers are unaware of data coding techniques and modern HDD technology or (more likely) that they offer these options to stop sales/use being lost to competitors, as users see them as more sophisticated offerings. Customer demand, in other words.

Gutmann worked on Winchester disk technology from the early 1990's, and he had the grace to acknowledge in his 1996 paper that later disks, which everyone outside of a musuem is now using, use different coding techniques that make his overwriting patterns irrelevant. He said that 'A good scrubbing with random data will do about as well as can be expected.' But nobody reads that part of his paper. I doubt whether many people have read any part of his paper.

In any event, how many users need super-secure deletion? Where are the armies of electron-scanning microsopes?

I think that the Gutmann myth is so entrenched that it will not disappear voluntarily. The only way to remove it is for software vendors to stop including it as part of their products.

As usual, I'll add my +100 to all of these comments. My highlight on the last sentence. Sadly the devs will not comment on this. They are happy for us to help other users with their products. But they are equally happy to hide away from arguments like this and let us keep repeating ourselves OVER and OVER again. Gutmann repetition.

[ident]

marmite, it's a year old thread mate, dunno why it was bumped

Nicely punned though

[marmite]

ident, on Apr 16 2010, 04:43 PM, said:

marmite, it's a year old thread mate, dunno why it was bumped

*coughs* oh yes, so it is

Same old problem though

[Nergal]

nO!!!! Bumper (reply #10) is a sneaky Spammer!!

[Alan_B]

cl5776, on Jan 27 2009, 01:18 PM, said:

Hi Augeas and login123. Thank you for the explanations. I just wanted to follow-up. The scan finally completed. It took 8 and a half hours but I recovered over 20GBs of space. I think you may have an idea as to what I am about to state next. Even though I now know that the Gutmann option is relatively pointless, I would be hard pressed to change at this point. I have been using Gutmann for so long that anything "lower" may seen inadequate. I may reduce down to NSA, though.

Thanks for your time.

You are new here so I will try to be patient.

If you do a bog standard simple deletion of 1 GB of disc space,
that will allow you an increase of 1 GB extra space to store things.

If instead you do a 35 pass Gutmann secure deletion on 1 GB of junk,
you do NOT gain 35 GB of extra space - only the original 1 GB.

It would be far better to spend 8.5 hours inspecting what is actually using disc space.
You may be able to delete a few GB of obsolete applications or music you no longer listen to.

N.B. If you discontinue Gutmann and simply delete, what is the worst that can happen ?
I can understand spending 8.5 hours to ensure a wife/girlfriend/kids do not see downloaded porn,
but Gutmann does seem extreme when you are concealing an addiction to music by Meatloaf or Kylie ! ! !

Alan

[ident]

"I have been using Gutmann for so long that anything "lower" may seen inadequate. I may reduce down to NSA, though."

inadequate? There is no recorded evidence of any one recovering one pass.

[Nergal]

ARRRG stop this is an old thread, silly users who've been here for a while read the dates to those you reply too



see picture with anotations