Does writing zeros to hard disk completely wipe out data ?

Discussion in 'General Hardware' started by xMax, Sep 10, 2005.

  1. xMax

    xMax Senior member

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    because ive downloaded balcco file shredder, and even after shredding my hardisk, i still was able to recover empty folder and file names on the disk. its almost like nobody wants you to be able to completely delete all information off your hardisk.

    so i figure, writing zeros to the entire drive should completely wipe out data beyond the point of any concievable means of recovering that data. i mean, how would the information be recovered if you write zeros to every binary string that stores data.

     
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  3. imported_Tick

    imported_Tick Diamond Member

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    Yes, but you need to write zero's several times. Writing zero's 7 time is considered adequate.
     
  4. 0roo0roo

    0roo0roo No Lifer

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    download eraser
    and yes,..7 times. and i thought they wrote random
     
  5. n0cmonkey

    n0cmonkey Elite Member

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  6. mechBgon

    mechBgon Super Moderator<br>Elite Member

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    DBAN is also considered good.
     
  7. meatfestival

    meatfestival Member

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    Wouldn't overwriting the hard disk with random data be better than zeros?
     
  8. Thorny

    Thorny Golden Member

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    Once you write 0's 7 times the polarity of the platters makes it almost impossible to recover ANY data on the disk down to the bit level. Random writes could still leave clusters that haven't been written enough times to be totally clean.

    Its kinda the same logic as a paper shredder, you don't want to leave any pieces big enough to read...

     
  9. mechBgon

    mechBgon Super Moderator<br>Elite Member

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    Yeah, several times. That's what DBAN does. Another option (for WinXP Pro and any Win2000 variant) is the cipher command, which overwrites any blank space with three layers of Encrypting File System-encrypted junk data, deleting it after each round. But I'd go with DBAN on one of its higher settings, if I were looking to blank a disk before letting a company PC go out the door or something.

    To use cipher, let's say you deleted all partitions on a drive and then created a single blank partition that's got drive letter F:. Start > Run > cmd and use this command line:

    cipher /w:F:\

    and off she goes. You can run cipher /w on your C: drive while using your computer, incidentally, it doesn't do any harm to existing data.
     
  10. n0cmonkey

    n0cmonkey Elite Member

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    You're wrong.
     
  11. Thorny

    Thorny Golden Member

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    Explain it then
     
  12. n0cmonkey

    n0cmonkey Elite Member

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    Read up on it.
     
  13. Thorny

    Thorny Golden Member

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    It's been several years since school, but in class we were told DOD standard (which we were left to assume was the best) was 7 writes. Not random. What about the Law of Probability? If your dealing with sensitive data do you leave anything to chance?

    I'm really not interested in reading up on it, I'm recalling something I was told years ago from memory. If I'm wrong, I'm sorry for spreading misinformation, but please at least explain it instead of just saying I'm wrong.
     
  14. xtknight

    xtknight Elite Member

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    Magnets? j/k. :p
     
  15. SunSamurai

    SunSamurai Diamond Member

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    Why do you think people come here, dipsh!t.
     
  16. n0cmonkey

    n0cmonkey Elite Member

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    Multiple overwrites is good, and ramdom over writes helps. The only really good method is destroying the drives.

    To quote from a paper on usenix:
    So, with multiple over writes of random types (0s and 1s, obviously), it'd be harder to get the original piece. If you over write it with just 0s, it'd be easier to find the original.

    IIRC the paper explains that the read/write arm in the hard drive won't get the exact same place every time, with makes finding the original easier.

    The DoD doesn't generally sit on its butt. I'm sure their standards have changed over the years. ;)
     
  17. n0cmonkey

    n0cmonkey Elite Member

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    To either ask questions that aren't answered anywhere else, or to be lazy jackholes and ask the same questions a million other people asked. Crawl back in your hole newbie.
     
  18. Thorny

    Thorny Golden Member

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    You sir, have enlightened me, and I stand corrected. Not sure how accurate your comment is about the DoD sitting on its butt is though ;)
     
  19. n0cmonkey

    n0cmonkey Elite Member

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    The government spends money.

    Overwriting hard drives better costs more money.

    The government over writes their disks better.

    Hell, they probably just incinerate the things (Nuke'em from orbit, it's the only way to be sure). ;)
     
  20. theMan

    theMan Diamond Member

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    hmm, how often do these threads come up, every three weeks? hahaha. i agree that the random writes are better than zeros, as long as you a lot of them obviously.
     
  21. pecel

    pecel Golden Member

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    Thanks for DBan link.
     
  22. Pr0d1gy

    Pr0d1gy Diamond Member

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    HAH, 0wn3d! Sorry N0c, but I'm going to have to disagree with your stance on this. I would rather discuss something on AT than go rummaging through the net if I could.
     
  23. Googer

    Googer Lifer

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  24. imported_BikeDude

    imported_BikeDude Senior member

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    But does that paper give some real-life examples? The theory looks nice and sound, but how about a practical experiment?

    And the latter part of what I quoted above "subtracting what is expected to be read" is somewhat ambiguous, is it not? (you've read 1.05, but expected 1.00, so you conclude the previous layer was a 1?)

    I've been dimly aware of this type of recovery since the mid-eighties, but after a brief e-mail exchange a few years back with a researcher working for IBAS, I got the distinct impression that such recovery is highly theoretical.

    NSA may (or may not) have technology to do this, but as with all things: Nobody knows what NSA are capable of -- we can only guess. NSA certainly isn't going to dissect xMax' hard drive to track down the deleted porn pictures he is hiding from his fiance! :D

    And all this assumes the file can be located... Although the file may not have been overwritten much, you still need to look at the file allocation table (or similar) and hope it hasn't been overwritten (too much), plus a fragmented file will present further difficulties. (I suspect NTFS will provide a steeper challenge than FAT -- I'm not too familiar with NTFS in this regard though)
     
  25. xMax

    xMax Senior member

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  26. xMax

    xMax Senior member

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    so its basically a ridiculously diffuclt process to try to permanently erase data off your disk. but i guess the bottom line is that what your all saying is that to revover data that has been overwritten 7 times, using random overwrites, one would need hardware tools, and not simply be able to hack into your computer from the internet and revover data using only software tools. because if thats so, then its not a problem for the average user whos not concerned about the government or some major organization stealing his computer and using gadgets and tools to recover the data.