One-ing a hard drive

Discussion in 'macOS' started by DisMyMac, Jul 10, 2010.

  1. DisMyMac macrumors 65816

    DisMyMac

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    Sep 30, 2009
    #1
    Is there a way to erase a hard drive by overwriting with 1's rather than 0's? (Disc Utility only allows 0's...)
     
  2. angelwatt Moderator emeritus

    angelwatt

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    #2
    See this thread, especially the questions coming as to "why" you want to do this.
     
  3. DisMyMac thread starter macrumors 65816

    DisMyMac

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    #3
    I'm amazed it's so difficult. I have extremely embarrassing things I want to erase. Nothing illegal, but if it were then I'd probably lie and say it was 750GB of online banking passwords.
     
  4. GGJstudios macrumors Westmere

    GGJstudios

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    #4
    If you use Disk Utility to do a 7-pass erase or a 35-pass erase, you'll be fine. There is zero chance of data recovery after that.
     
  5. sjinsjca macrumors 68000

    sjinsjca

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    Oct 30, 2008
    #5
    That thread doesn't answer the "why".

    Specifically: why is even a single-pass wiping not sufficient?

    Disk Utility lets you wipe your drive by randomly overwriting blank space and deleted files up to 35 times. Random is better than 1s or 0s if you're concerned about physical forensics being attempted on your drive. And physical forensics is becoming pretty close to impossible with today's dense drives.

    If even 35-pass wiping is not good enough, you really might want to consider going to your local computer store and getting a fresh hard drive, then taking a hammer to the old one, roasting it at high heat to destroy all magnetism, etc. Frankly that might be faster than a 35-pass wipe, too.

    And keep in mind that any wiping is a severe exercise of the drive. If it's not fairly new, you might find it doesn't survive the process, or fails shortly after.
     
  6. snberk103 macrumors 603

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    #6
    I'm with sjinsjca. If you are that worried about the contents, then take a hammer and pound all the 'ones' you can into it. Then a drill, and put some 'zeros' into it, just to be sure. :)
     
  7. strausd macrumors 68030

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    Texas
    #7
    Not only when your data be safe, you'd have fun destroying it :)
     
  8. sjinsjca macrumors 68000

    sjinsjca

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    #8
    We're still wondering why you want 1s instead of 0s. Or, better, random 0's and 1's.
     
  9. angelwatt Moderator emeritus

    angelwatt

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    #9
    I didn't claim it did. I wanted him to read that people were asking why you'd want to do this, which is what I wanted the OP to ask himself, because there's no point to it.
     
  10. lewis82 macrumors 68000

    lewis82

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    #10
    Most probably because 1's imply magnetism, while 0's imply the absence of magnetism, and thus a greater chance of recovery.

    IMHO a 7-pass is sufficient. If it is just pr0n then don't bother (unles it is of a more illicit kind, but let's not start a debate), just erase it once.;)
     
  11. sjinsjca macrumors 68000

    sjinsjca

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    Oct 30, 2008
    #11
    Agreed, even a one-pass would be very secure and less likely to toast the drive. But 7 passes with random data would really put paid to anything.

    Besides, he said "embarrassing" not "illicit." I imagined homemade videos of Jedi impressions complete with plastic light-sabers, or something...
     
  12. sjinsjca macrumors 68000

    sjinsjca

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    #12
    BTW that's not how it works. Today's drives write their data by flipping magnetic domain orientations. In any case, random would be much more obscuring than a constant pattern.
     
  13. chown33 macrumors 604

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    Aug 9, 2009
    #13
    That's not how magnetic recording works.

    Indeed:
    http://en.wikipedia.org/wiki/Gutmann_method#Criticism

    The 7-pass and 35-pass options exist in Disk Utility primarily because some companies have that as a policy. So it's more about meeting customer policy requirements than any demonstrated technical need.
     
  14. lewis82 macrumors 68000

    lewis82

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    #14
    Well I know it's not the way it works. If I understand well, it's about the alignment of the magnetic material inside.

    But still, you get the idea. 0 = empty, 1= full.
     
  15. DisMyMac thread starter macrumors 65816

    DisMyMac

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    Sep 30, 2009
    #15
    I guess there's really no point to it. 0's will do.

    Thanks. ;)
     
  16. mac2x macrumors 65816

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    Sep 19, 2009
    #16
    Better still for making those 'zeros': take it out to the range and shoot it. :cool: Just to warn you though, hard drives are impervious to .22s; you'll need something bigger. :D
     
  17. MisterMe macrumors G4

    MisterMe

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    #17
    No. That's not how magnetic recording works. Magnetic recording works by changing the direction of magnetization in adjacent magnetic domains. Consider these cases:
    • Domain 1 is up. Domain 2 is up. This is a 0 bit.
    • Domain 1 is up. Domain 2 is down. This is a 1 bit.
    • Domain 1 is down. Domain 2 is up. This is a 1 bit.
    • Domain 1 is down. Domain 2 is down. This is a 0 bit.
    This is simplified and does not include the use of timing bits. But the basic principle holds. Magnetic recording requires changes in the orientation of adjacent magnetic domains to represent a 1 bit and no change to represent a 0 bit.

    We did not get into the silly premise of this thread. The silliness surrounds the fact that if anyone is interested in your data, then they are much more likely to be interested in it before you discard your hard drive than after. There are ways to capture your data before you dispose of your hard drive. Barn doors, horses, and all that.
     
  18. Sean Dempsey macrumors 68000

    Sean Dempsey

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    Aug 7, 2006
    #18
    There's only one thing that is embarassing enough that it

    a) requires complete obliteration
    and
    b) is something someone else would be looking for



    But anyways, a 750gig drive is like, 50 dollars? Why not just be SURE your data is gone:
     

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  19. Heilage macrumors 68030

    Heilage

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    May 1, 2009
    #19
    As others have suggested, destroy it physically. Demagnetize it completely, make sure that there is no way to actually read the hard drive platters.
     
  20. iBunny macrumors 65816

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    Apr 15, 2004
    #20
    Just know that I am in the department for data recovery and forensics etc and a single pass of zeros if more than sufficient if data is written back over it.

    So wipe zeros to the drive, then format and install your OS and stuff, defrag and call it a day. I would never be able to get any info off that drive, even with thousands of dollars in equipment/software.
     
  21. MacTech68, Jul 12, 2010
    Last edited: Jul 13, 2011

    MacTech68 macrumors 68000

    MacTech68

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    #21
    Exactly. The idea that any average or "power" user could retrieve any data from a drive that has had zeros written on a single pass is preposterous.

    If you think that a secret government department is going to attempt it then perhaps a 7 or 35 pass is required. :rolleyes:

    Filling the drive with dummy data after writing zeros is a good idea, but is unnecessary if you only want to prevent the next average joe from recovering your old data.
     
  22. pilotError macrumors 68020

    pilotError

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    Long Island
    #22
    I prefer to throw the drive down hard on concrete and shatter the platters.

    Unless your running from the NSA or CIA, then fire would probably be a good idea :D
     
  23. lewis82 macrumors 68000

    lewis82

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    #23
    All right. Let me explain what I mean. :rolleyes:

    In folklore, 0, the number, is a synonym of empty, void, nothing. 1 is the opposite. It means something, full, etc.

    Now I didn't explicitely say that a 0 on the hard drive is no magnetism and a 1 is some magnetism. I know it's far more complicated than that, it involves giant magnetoresistance, perpendicular recording and all sorts of technology I only onderstand partially. But, I do know that it is not 0 = no magnetism, 1 = magnetism. And anyways, it is not even what I was talking about.

    What I meant was that, as I could understand it, 1's were more secure in OP's mind, because 1 have historically been associated with a quantity, whereas 0's are associated with the absence of something.
     

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