How to erase data before selling Macbook?

Discussion in 'MacBook Pro' started by jneckert, Dec 3, 2007.

  1. jneckert macrumors member

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    Nov 23, 2007
    #1
    Help! I am hoping to sell my Macbook via Craigslist this week and I need to erase all the data. I backed up to an external hard drive using Superduper. I started the erase and install using the Install disk but I'm concerned that the files will be recoverable. Can I still zero out the hard drive after the erase and install is done or is this sufficient?
    Thanks.
     
  2. Big-TDI-Guy macrumors 68030

    Big-TDI-Guy

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    Jan 11, 2007
    #2
    There is software that will do this.

    If on your own, you could copy and duplicate a large video file, or audio files. Fill up your hard drive with that, then use "secure empty trash" -- Better to do it when you're about to go to bed, or work for the day. (can take a while)

    That should wipe it clean enough for "most" concerns.

    The (#*$ I use at work is INSANE, takes 30 minutes to wipe a 2 meg file. I think that is overkill - even for what I do... But then again...
     
  3. jneckert thread starter macrumors member

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    Nov 23, 2007
    #3
    Thanks. I'd rather just secure erase using disk utility. But since I already started erase and install disk I'm not sure if I can still secure erase the drive.

    Anybody have any suggestions?
     
  4. xUKHCx Administrator emeritus

    xUKHCx

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    The Kop
    #4
    And that software is called Disk Utility.

    Boot from the install DVD and open up Disk Utility from one of the menubar options, cant remember which one. And select the volume, then go to the erase tab and then set your security options. 7 pass will basically give you as much security as you could possibly want set it going and leave over night.

    You will of course have to reinstall the OS but that only takes 30 minutes.
     
  5. jneckert thread starter macrumors member

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    Nov 23, 2007
    #5
    If I started the erase and install first can I still use disk utility?
     
  6. sndcj1 macrumors member

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    May 22, 2007
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    Chicago
    #6
    If you boot from your install disk, before you install the operating system, on the top menu bar, you can select disk utility. Select your main drive from disk utility, set your "Security Options..." and then tell it to erase the drive. You can do a Zero data, 7 times pass, or 35 times pass. I would think zero out or 7 times pass at the most would be sufficient for your needs. This will take a LONG TIME, especially if you choose the 7 times overwrite. After it is done, quit the disk utility, and re-install the system.


    edit. I guess i type to slow, xUKHCx beat me to it. And yes, you can still wipe the disk after you do an erase and install.
     
  7. xUKHCx Administrator emeritus

    xUKHCx

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    #7
    Yes, what stage are you at?
     
  8. jneckert thread starter macrumors member

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    Nov 23, 2007
    #8
    On Install Disk 2. Just started...
     
  9. Big-TDI-Guy macrumors 68030

    Big-TDI-Guy

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    #9
    The software I referred to was DOD compliant. The "quick erase" feature at work consists of 256 write/rewrite cycles. And this isn't even on a secure network. I have no idea what they use for that.
     
  10. xUKHCx Administrator emeritus

    xUKHCx

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    #10
    Seeing as i left the forums lastnight before coming back to this thread chances are that the install has completed by now, sorry. So just go ahead and boot from the install DVD 1 and run disk utility as described above.
     
  11. GadgetNeil macrumors newbie

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    Nov 29, 2007
    #11
    What about Graveyard - it's a freeware app I downloaded that purports to do a more permanent erase of files/apps - would it delete things in a way that is nonrecoverable?
     
  12. xUKHCx Administrator emeritus

    xUKHCx

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    #12
    The thing is that only deletes files as you delete them, there are plenty of other files that will not pass through this that could contain sensitive data. Whenever you are going to sell a computer it is always best to erase the data as described above.
     
  13. RichardF macrumors 6502

    RichardF

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    #13


    Boot up with your Tiger/ Leopard Restore disc and do a 35-pass in Disk Utility. Make sure you highlight the entire drive in the left column and not just the Macintosh partition.

    It took close to 48 hours for me on a 100GB drive in a 17" Powerbook G4 1.67GHz with a Tiger restore DVD.

    After that nothing it's almost impossible to recover anything from the actual hard drive platters, not even with microscops and professional equipement/ software.

    Just because I am paranoid, I actually did the 35-pass twice!
     
  14. xUKHCx Administrator emeritus

    xUKHCx

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    #14
    35 Pass is a tad overkill really for the general public

    If you are that paranoid why didn't you physically replace the HDD.
     
  15. Watermonkey macrumors member

    Watermonkey

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    #15
    All I've ever heard from the computer radio shows is the only way to be sure your data can't be recovered is to physically destroy your hard drive. Otherwise, just buy a new drive to sell with the computer and keep your old drive in an enclosure as a outboard drive.
     
  16. Jack Flash macrumors 65816

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    #16
    And to be honest, how worried are you about someone recovering your data? Zeroing a Disk is very hard on it. I would not suggest a 35 pass wipe.
     
  17. Big-TDI-Guy macrumors 68030

    Big-TDI-Guy

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    #17
    That is actually true - IT dept at work hates our data destroying software b/c they claim it causes the hard drives to fail almost 3 times faster.

    Logically it makes sense, you are putting a hell of a lot more work on the read/write head and platter.

    But then again - 100 dollar HD vs the consequences of the data being used by a 3rd party...
     
  18. sndcj1 macrumors member

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    #18
    Besides theoretical documents talking about it, I have been unable to find anything that will recover data on a wiped drive. Now, I am talking about programs that can be purchased, but most of the data recovery people also have data destruction programs that all say once you run this there is no way to recover the data. I'm guessing if the FBI is after you, they might have some tools up their sleeves, but most people don't have multi-million dollar clean room labs to ATTEMPT to recover partial data from your drive. As far as the sensitivity of head reader built into your drive, it wouldn't make much sense for the drive manufacturer to create something that reads files that have been overwritten. If that were the case, every time the drive got full (or you had written/deleted enough to make it full), all your new files would have parts of the old files on them. Unless I'm mistaken, we're talking about something with essentially 2 states. 0 or 1. Now the theoretical stuff is about the ability to read something that is 0.0001 and assume that the last position of that byte was intended to be a 1, not a 0. Now you've got to do that to about 24000 associated bites to create a 3k file. This, of course, is after you have flipped the bites 7 or more times. The idea is that it can be done, but the ability of a user, or even some data recovery center (as they specialize in accidental/failure issues), to do this would be essentially non-existent.

    All that being said, if your still worried, the only guaranteed way to destroy data, is to destroy the drive. Fire/acid on the open platter would be best.
     
  19. DataThief macrumors member

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    #19
    11 passes is usually good, I had a customer site that after replacing a HDD in their server the owner was vary paranoid about me taking the bad drive, I asked him if he minded the extra charge for the drive and he said no, so I opened the drive and smashed the platters into dust. He was very happy, I thought he was nuts.
     
  20. Big-TDI-Guy macrumors 68030

    Big-TDI-Guy

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    #20
    From a personal level - I don't think anyone has to worry that much. But trust me - data recovery is big business - you'd be surprised. From a corporate or DOD standpoint - there are plenty of others with the capability and desire. For "honest" Joe Schmoe - I wouldn't lose too much sleep over it.
     
  21. Type121 macrumors regular

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    #21
    I wish I could find the article right now, but I recently saw an article that referenced a study that basically found that after one pass, laboratory techniques were unable to recover any previous data and the whole 7 or 35 pass thing was a reaction to untested beliefs. Gotta dig that up.
     
  22. bokdol macrumors 6502a

    bokdol

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    #22
    once it is all installed you dont have to erase the drive again. disk utility will wipe just the free space up to 35 times.
     
  23. jneckert thread starter macrumors member

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    Nov 23, 2007
    #23
    No problem. I ended up doing an erase and install doing a one-pass erase with disk utility. Then I had to install OSX again but I feel better.

    Not really necessary. I just wanted to make sure passwords for accounts and personal data was unrecoverable. I guess if someone tries hard enough they can find it. I didn't want to replace the hard drive b/c my new computer has a 160GB drive and the 80GB drive in the Macbook I sold wouldn't have been much use to me. I do appreciate the help and input as always from fellow Mac users.
     

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