MacOS – How to Wipe a Disk from a Mac with Firmware Password Set

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I'm in a somewhat odd situation: I need to wipe the disk of a MBP, but I can't boot into Recovery Mode/from a CD/etc. as there is a firmware password set.

Is there a way to wipe the disk from within the OS? (I guess the answer will likely be no, but I had to check). Or maybe just to "remove" the encryption password from the HD so as to make it unreadable?

I've been looking around and have found several ways of wiping files (srm, "Permanent Erase", etc) but if possible I'd like to be more thorough.

PD: A bit of background to explain how I got to be in this situation: I've been doing some work for a company where they use Macs so they've loaned me a laptop configured as per their policies (encrypted drive, firmware pwd, etc); once but I've finished the project I have to return the laptop but I'd like to clean it up as much as I can before handing it back.

Best Answer

You can just delete the files and use Disk Utility's Erase Free space feature to make them permanently gone. Open Disk Utility, go to the partition you want to clear, select the Erase tab and click on Erase Free Space... This will give you options that depend on your OSX version.

  • a slider with the settings Fastest, Secure and Most secure represent 1-pass, 3-pass and 7-pass wipes respectively.
  • radio buttons labeled Zero Out Deleted Files, 7-pass Erase Deleted Files and 35-pass Erase Deleted Files are quite self-explanatory

You may want to first go with a single pass to get an idea how long a single pass takes and then depending on your time allocation (or paranoia) choose between the multi-pass wipes. Note that 7-pass is good enough for NSA.

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