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I wanted to say "remove the hard disk" but with Macs that's not an option anymore, so if there's sensitive data on it I'd personally do a full backup and then w

I wanted to say "remove the hard disk" but with Macs that's not an option anymore, so if there's sensitive data on it I'd personally do a full backup and then wipe the disk using a factory reset before sending the device in. Who knows where it might end up? Even if the disk is encrypted there might be a way to decrypt it in the future (e.g. firmware issue, weak password etc.), so the only way to be sure is to completely purge all data. And selectively deleting stuff is a bad idea, even if the disk is encrypted the file system will usually not overwrite the files on deletion, i.e. if someone manages to bypasss the full-disk encryption the files might still be recoverable (unless you use "shred" to overwrite them, which has its pitfalls as well if used on single files).

AnonC 4y ago
I think wiping the disk using factory reset isn’t going to wipe or overwrite the data though, especially on SSDs. If you try to overwrite files or sectors, that may not actually overwrite those specific sectors either. All unencrypted data may be available to read. My guess is you’re out of luck if you don’t trust full disk encryption when it’s done right from the beginning of using the machine. Physical destruction isn’t cost effective when the machine is sent for repair.
- jonnycomputer 4y ago
  Is it possible to securely wipe a SSD? Or better to encrypt whole drive, throw away the key, and maybe corrupt a few random bits?
  - AnonC 4y ago
    Yes,that’s certainly possible with the response that bitwize provided in a reply to your comment. But the GP doesn’t trust full disk encryption or the firmware. For such people, there is no way other than complete physical destruction.
  - bitwize 4y ago
    There is a "Secure Erase" command in the ATA command set that pretty much does just this. Modern SSDs have firmware-level encryption with a hidden key only the firmware knows; Secure Erase simply obliterates and regenerates the key.

AnonC 4y ago

I think wiping the disk using factory reset isn’t going to wipe or overwrite the data though, especially on SSDs. If you try to overwrite files or sectors, that may not actually overwrite those specific sectors either. All unencrypted data may be available to read. My guess is you’re out of luck if you don’t trust full disk encryption when it’s done right from the beginning of using the machine. Physical destruction isn’t cost effective when the machine is sent for repair.

jonnycomputer 4y ago
Is it possible to securely wipe a SSD? Or better to encrypt whole drive, throw away the key, and maybe corrupt a few random bits?
- AnonC 4y ago
  Yes,that’s certainly possible with the response that bitwize provided in a reply to your comment. But the GP doesn’t trust full disk encryption or the firmware. For such people, there is no way other than complete physical destruction.
- bitwize 4y ago
  There is a "Secure Erase" command in the ATA command set that pretty much does just this. Modern SSDs have firmware-level encryption with a hidden key only the firmware knows; Secure Erase simply obliterates and regenerates the key.