Secure Deletion in Ubuntu.

I use the secure delete suite (including srm and sfill) which overwrites files and free space multiple times.

I know there is also shred and dban (though I believe for entire drives rather than specific files).

There was some debate at ubuntuforums.org as to whether srm actually worked properly. I wonder what people think of it?

Also, I recently read "Overwriting Hard Drive Data: The Great Wiping Controversy" which suggested (although I did not understand all the technical details) than people should not worry so much about undeleting data and a couple of overwrites is sufficient.

http://www.google.com/search?hl=en&...&gs_rfai=&emsg=NCSR&ei=ckK3S9qTOZP49ATrxr3bDg - first link leads to .pdf file.

Any thoughts on both these issues?

As always, thanks!

 

sudo apt-get install secure-delete

 

I took part in that discussion over at the Ubuntu forums. And, yes, I think secure-delete does what it claims to do. All it does is write 1's and 0's to the drive sectors, which is the same thing Bcwipe, dd, and shred do.

Those who say data can be recovered from modern hard drives after it has been overwritten are simply ignorant of the facts and the studies done. If you think about it, it doesn't even make logical sense to claim one can recover the data because that assumption presupposes that hard drives have almost infinite capacity (if you can recover all the data on a 1 TB drive that was previously there, that would mean the drive has 2 TB of capacity, which is a logical fallacy).

 

Like filling a full cup of water with another full cup of water and somehow they are both in the same cup with no overflow.
But it can't be that simple or else people wouldn't recommend 7passes or 35 passes to eraser/destroy/wipe data.

 

It is all a question of how much money (think exotic equipment) and time to throw at a target. They (gov't) can, and have done so in the past - so, don't foot yourself into believing what you think makes logical sense when the real experts can and will (with motivation) find out - so, do yourself a favor, and don't do anything illegal.

-- Tom

 

Bingo. It doesn't make sense does it?

This whole 35 pass business started with Peter Gutmann's paper back in the 90's. A lot has changed with hard drive technology since he wrote that paper and even he himself now says "a couple of passes is about the best you are going to get." The paper I cited in my previous post says that more than one pass is overkill.

I don't look at the govt. as being an all powerful entity that can break the laws of physics just because they have lots of spooks and money. There is no evidence whatsoever that they have recovered data from a modern hard drive that has been overwritten with random data once.

 

If government was that powerful, they wouldn't get hacked with regularity, that too by university students, albeit brilliant students nonetheless.

 

For Linux just use hdparm, to access secure erase feature, to wipe whole disk and restore from backup.
If you need to delete individual files or groups of files then dd, shred or whatever you prefer.

For whole disk wiping, time is an issue; The secure erase function being the most complete in the least amount of time. Usually wiping a 300gb drive in approximately 80 minutes.
If you have the money, Ultrastar or Cheetah drives support enhanced secure erase wiping @ 100gb per second.

I am not interested in waiting 13 hours wiping a drive. Forget about 35 passes, days of waiting.

Individual file wiping with shred:

Code:

shred -z -u -n 0 /path/to/file

 

'n' = 0 ?

Does this mean that your file is not overwritten at all?

Code:

shred -uvf -n 35 <file>

takes a second to run on a word document less than 1MB in size.