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Windows 7: I need more than 1 pass in Shredd Method?

11 Jul 2011   #11
FliGi7

XP / Win7 x64 Pro
 
 

So, there are two issues here...

1) Erasing a single file so that no trace is left behind

This requires overwriting the file, overwriting and temp files related to it (if it was ever auto-saved somewhere), erasing any remnants of it in system restore points, erasing links to it in the current registry (.LNK files, MRU's), erasing links to it in system restore point registries, and removing it from the MFT which requires knowing where it's stored in the MFT and erasing that block of information. Your best bet is to do as many of these things as possible and hope your system randomly overwrites the remaining info at some point in the future before someone else tries to find traces of the file.

2) Erasing a hard drive

This requires writing zeros (or random data or whatever you want) to a drive using something like DBAN or DD. It doesn't care whether the space is unallocated, temp storage, or anything of the sort. It writes zero's to the entire readable drive space so that nothing in any space on the disk is recoverable.


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11 Jul 2011   #12
Bare Foot Kid
Microsoft MVP

W 7 64-bit Ultimate
 
 

You do not need 3rd party software, Windows will do it all, single files or entire HDD / SSDs.

Secure Erase / Wipe : Definition and Methods


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11 Jul 2011   #13
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

OP was just asking if one overwrite was enough.
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11 Jul 2011   #14
Bare Foot Kid
Microsoft MVP

W 7 64-bit Ultimate
 
 

Quote   Quote: Originally Posted by Britton30 View Post
OP was just asking if one overwrite was enough.

For most instances it is.
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11 Jul 2011   #15
FliGi7

XP / Win7 x64 Pro
 
 

Sdelete doesn't delete registry information as stated above, nor do I see that it deletes this data from system restore points (maybe it does, but it didn't say so in the tech description here SDelete). Sdelete securely deletes the file data so that the file is not recoverable (although it doesn't address restore points, which would allow for recovery of the file if not deleted), it doesn't appear to delete all traces of it having been there. There is a difference in being able to recover a file and being able to find traces of it, as I pointed out above. It depends on what the user is looking to do. The OP talks about just erasing the data then asks paranoid questions about how to make sure it's completely gone, so I'm not sure what they're actually looking to do here.
My System SpecsSystem Spec
11 Jul 2011   #16
seventrad

Windows 7 Ultimate x64 SP1
 
 

Quote   Quote: Originally Posted by FliGi7 View Post
The OP talks about just erasing the data then asks paranoid questions about how to make sure it's completely gone, so I'm not sure what they're actually looking to do here.
What I doing here? I'm looking for information!

I do this question because I'm confused about that Peter Gutmann believes:

"Gutmann claims that intelligence agencies have sophisticated tools, including magnetic force microscopes, which together with image analysis, can detect the previous values of bits on the affected area of the media (for example hard disk)." ("Criticism" section)

Gutmann method - Wikipedia, the free encyclopedia

I need to believe in secure references: Gutmann is Ph.D in Computer Science. He is specialist in cryptographic and computer security.
Peter Gutmann (computer scientist) - Wikipedia, the free encyclopedia

I searched about this question in other forums. Many people said different things.

Now, after the help all of you, I'm more secure about this matter. Especially after the Britton30's post.

Thank you all for the help!
My System SpecsSystem Spec
12 Jul 2011   #17
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

Glad you have the info you wanted seventrad.
Guttman did his theorizing and testing in the mid 90's, so most of what was true then, of course, doesn't apply now. It is interesting to read about his methods though. His reasoning of a 35-pass overwrite was to prevent electro-magnetic scanners or electron microscopy to recover data.

Footnote:
A group of Purdue University students, as an experiment, went out and bought several HDD's a few years ago. They were used and thought to be clean or non-functioning. they were able to recover passwords, email accounts, bank account numbers, pictures, medical records and more. The drives had all been at least reformatted too.

Quote   Quote: Originally Posted by seventrad
If when I use a "erase software" with only 1 pass or when data is overwritten by another file of SO (data file, mp3, movie...), why exists many software with many methods of data erase (CCleaner, Eraser, Active@ Kill Disk, PGP...) ?

All those were aimed at pre-2001 hard drives. The military and security agencies had the need for secure erasure, so developed those methods. These are all uneeded now to get the same level of erasure.
Of course the developers/vendors of these products want to keep selling them.
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12 Jul 2011   #18
Golden
Microsoft MVP

Windows 7 Ult. x64
 
 

Quote   Quote: Originally Posted by FliGi7 View Post
The multiple passes date back to hard drives of many generations ago where data storage was much less dense and provided for greater ability for recovery with very sophisticated software. Current hard drive density doesn't nearly as easily allow for such things any more, so the multiple passes are for added feeling of security rather than actual. Data overwritten once on any remotely recent hard drive is gone. At best, with very expensive microscopy equipment, parts of sparse data could be recovered, but even then you'll be lucky to find anything contiguous or that you'd be able to piece back together into something whole.
+1. All that is needed is method 3 in BFK's tutorial Secure Erase / Wipe : Definition and Methods
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 I need more than 1 pass in Shredd Method?




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