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When erasing a drive with Disk Utility, you have a couple options. An insecure wipe, a single pass of zeroes, a "DOE-compliant" 3 pass, and a DOD (Department of Defense) 7 pass.

DOE doesn't stand for Department of Energy, does it? That sounds silly.

  • Sure it sounds silly that the Dept. Of Energy would have a wiping standard (especially since the DOD has one) but remember that a lot of our nuclear tech is under the DOE's jurisdiction. – moneyt Dec 21 '17 at 18:49
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DOE is a method to wipe disks, developed by Department of Energy as part in their manual to ensure the confidentiality of Department of Energy information.

From macs.about.com :

When Disk Utility uses the DOE-compliant 3-pass secure erase, it will write two passes of random data and then a single pass of a known data pattern. This will take anywhere from a day to a week or more, depending on the size of the drive. You can run this stress test in the background while you use your Mac for other activities.

  • 2
    The answer is correct, but the thing about “3-pass” secure is the whole methodology of going over a disk multiple times is based on old hard drive technology where sectors & tracks were so wide there was a risk of residual data being still in place. Meaning with the right tools to amplify or slow down the drive, one could recreate data. But modern hard drives all have such tight tracking & multiple platters a simple zeroing out of data once is enough. – JakeGould Feb 16 '13 at 7:20
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    Here's an article on HowToGeek backing up JakeGould's claim that only one pass is required. – hunse Dec 18 '15 at 0:45
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    In response to JakeGould and hunse above (I'd love to comment in the appropriate place, but one does not simply sign up for Ask Different and post comments), while the 35-pass Gutmann wipe described in the linked article is certainly unnecessary, a simple wipe, writing 0s to all sectors, is still not necessarily sufficient to prevent even a sophisticated adversary from recovering data. When the data currently written to each sector is known, it may (depending on precisely how the drive operates, tolerances, etc.) be possible to discover what was previously written. The article does nothing to – Alfred Dec 21 '17 at 18:18
  • refute this. The 3-pass DoE compliant wipe mitigates this by writing two passes of random data before setting the drive to a known state (likely by zeroing it). After this procedure, it should be impossible to recover data even by bypassing the drive's internal read/write hardware. However, simply zeroing a drive should be sufficient to prevent anyone from recovering data without modifying it in some way. – Alfred Dec 21 '17 at 18:18
  • Note that this does not apply to SSDs, as it is not possible to predict what data will be overwritten when a block's contents are modified. Encryption should be used instead, as simply destroying the key makes any data effectively irrecoverable. (Not to mention, flash memory can only be written a limited number of times before failing, so even if possible, wiping an SSD by overwriting its contents would reduce the drive's lifespan.) – Alfred Dec 21 '17 at 18:18

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