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I ran DBAN with eight passes, and then I ran it with one pass again.

Does that mean my hard drive is as secured as with one pass, or with eight?

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There seems to be a fundamental lack of understanding of what it is DBAN does, and how overwriting works. Overwriting once doesn't mean your previously 8 times overwritten data will magically reappear from somewhere. –  Karan May 4 '13 at 2:00
    
@Karan Thanks! I'm paranoid. Could you answer me this question? link –  Napat Maipaiboon May 4 '13 at 2:09
    
Those are different data sanitization methods/standards used by different organizations across the world. Going into each one of them in detail is not possible here, but you can get an overview of each here. Look, in general a couple of passes is sufficient to make most data unrecoverable. You shouldn't even bother about it this much unless you're desperately trying to hide evidence of some sort of major illegal activity from an organization with lots of resources, in which case just physically destroy the drive. –  Karan May 4 '13 at 13:25
    
@Karan No,It's legal.I'm afraid only repairman. each methods has only number of passes differently? Am I think right? –  Napat Maipaiboon May 4 '13 at 18:58
    
Number of passes and what's written on each pass, plus maybe some quirks here and there. Like I said, any of them should do unless you have unusual requirements. –  Karan May 4 '13 at 20:57

2 Answers 2

up vote 3 down vote accepted

No, it's not true. If you overwrite the disk 8 times, and then you overwrite it 1 more time, that's 9 passes total.

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My harddisk has more security? I'm afraid 8 pass that i ran before is wasteful. –  Napat Maipaiboon May 3 '13 at 12:33
    
@NapatMaipaiboon - If you already ran it what does it matter? Wiping your drive 8 times is about 6 times to many. –  Ramhound May 3 '13 at 12:41
    
@Ramhound I'm sorry.I think "wasteful" same meaning "lost". –  Napat Maipaiboon May 3 '13 at 12:57
    
@NapatMaipaiboon - They mean two entirely different things. –  Ramhound May 3 '13 at 13:24
    
@Ramhound Sorry again and thanks for your answer. –  Napat Maipaiboon May 3 '13 at 13:30

The way DBAN works is it generates pseudo random numbers and writes them to the disk. Depending on the overwrite method used it simply changes the pattern of the writes. What this does is prevent the reconstruction of the data.

Running DBAN with 8 passes and then with 1 additional pass is does nothing different than just running it 9 times.

For example, using the DoD 5220.22-M standard in 3-pass method would write the following:

Pass 1: 0000000000 Pass 2: 1111111111 Pass 3: 1832810292

Now if you were to run it again with just 1 pass you will get:

Pass 1: 0000000000

So basically you've just re-written 0's over the data you already wrote over.

Also the NIST has stated that with today's current hard drive standards that one pass is actually sufficient to render the data near impossible to recover.

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Thanks. So my harddisk is more security. Am I right? I'd like to know what is different between method names(e.g. RCMP TSSIT OPS-II , quick pass)? –  Napat Maipaiboon May 4 '13 at 1:59
    
    
I also believe that the readme file has the short description of quick pass or it tells you what it is. Simply Google the methods because they are "standardized" methods that aren't just for DBAN. –  Travis May 6 '13 at 12:38

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