Securely Format a Mac Hard Drive
If you want to be absolutely sure your data is wiped clean with virtually no chance of recovery, look no further than Apple’s Disk Utility tool. The process is simple.
How to Secure Format a Mac Hard Disk Drive
- Launch Disk Utility (located in /Applications/Utilities/)
- Select the drive you want securely formatted
- Click on the ‘Erase’ tab and click the “Security Options” button
- You’ll see four available choices, the second two are what we’re looking to use
- Select either 7-Pass Erase or 35-Pass Erase, depending on your needs
- Click OK
7-Pass Erase is pretty thorough and it meets the US Department of Defense standard for securely erasing media, by erasing the data then writing over it seven times. If that’s not secure enough for you, 35-Pass Erase is even more intense and provides exceptional data deletion security by erasing the data then writing over it 35 times, which should make data recovery virtually impossible. Because both 7 and 35 pass are writing over the data repeatedly, the length of time it takes to format the drive in this manner can be considerable (particularly 35 pass since it is doing this 35 times in a row), and it’s not unusual on a larger drive for this secure formatting process to take 24 hours!
Of course, if you’re not looking to re-use the hard disk, the most secure known method of wiping a drives contents from the face of the earth is to format the drive using an above method and then simply physically destroying it in a thorough manner.
The 35-pass erase option is generally considered pointless & a waste of time these days. Even at the time of writing in the ’90s the author of the 35-pass method said it was a ‘catch all’ to cover all types of HD technologies around at the time so was an overkill approach. Since then the author has criticised how his algorithm is over-prescribed for data scrubbing.
See:
http://en.wikipedia.org/wiki/Gutmann_method#Criticism
One might also argue that the 7-pass is overkill too unless you truly believe that someone so intent on reading your data that they’ll crack open your hard disk and analyse the magnetic wave forms on the platters directly, for this is what it would take to read the previous data once the HD has truly overwritten it with some other data.
So unless you have paranoid delusions or are James Bond, the ‘zero out data’ option is just fine for the average user.
Of course, the last point in the OP about physically destroying the disk is still the most reliable method to erase data. Drills or Steamrollers spring to mind here. Though you might want to extract & save the magnets in the drive that control the heads, they’re incredibly strong for their size so can be really useful.
While doing this and selecting the Hard Drive, the option of SECURITY OPTIONS is grey and cannot be highlighted and under the FORMAT dropbox it reads MAC OS X (JOURNALED). Whats wrong or what is the next step to format the hard drive and perform a clean install?
[...] Options” button is greyed out in the Disk Utility options, seemingly preventing a standard “secure” erase procedure. The precise reason for this isn’t entirely clear, though some speculate it’s [...]