Older external drive enclosures

[josehill]

If you are going to go to the trouble of smashing disk platters with a hammer, be sure to wear proper eye protection. A scratched cornea is no fun.

[Shamino (David C.)]

Yes. And put it in a bag during the smashing, so you can capture all the shards.

[schwartz (Dana Schwartz)]

“palimpsest”

[Shamino (David C.)]

@mschmitt

more interesting is the problem with SSDs, which contain more pages of data than are currently exposed to the operating system in the file system. If you use the OS to overwrite the data, it will not actually erase all of the pages – it can’t see the pages that are in reserve. What’s needed is to send a wipe command to the SSD drive, and let it do the secure erasure.

Yes. But…

• After you write zeros to a block, the data may remain for a while in flash cells marked as “garbage”, but that data is inaccessible via the normal SATA/NVMe interface.

• If you can remove the flash chips from the board and read them directly, you can probably see whatever garbage is left behind.

• I think it should be possible to install modified firmware into an SSD controller to allow access to garbage blocks.

  I have not heard of anyone doing this, but I would be really surprised if such firmwares don’t exist, either as manufacturer debugging tools or as forensic toos for law enforcement.

• The purpose of TRIM is to immediately mark blocks (possibly the entire device) as garbage. Effectively the same as writing zeros to everything, but much much faster and without creating excessive stress on the SSD.

  When the actual garbage gets collected will still be an implementation detail

• There are actual “secure erase” commands in the ATA/SATA protocol and (if I remember correctly) the NVMe protocol, which, if implemented properly, should force immediate garbage collection.

• If you’re on a Linux system, there is the blkdiscard command which can quickly TRIM-away devices or regions of devices. It has a “secure” option which will also purge garbage, if the target device supports the feature.

• But all of the above is moot if you use encryption. If you’ve encrypted the device, then all you need to do is discard/forget/lose the key and that’s that. The data will be unrecoverable.

  Ever since the introduction of the T2 chip in Intel Macs, Apple has always encrypted the internal SSD. Wiping the device using Erase all content and settings, should do just that, quickly and easily destroying everything not pre-installed by Apple.

[mschmitt (Michael Schmitt)]

@Shamino

• But all of the above is moot if you use encryption. If you’ve encrypted the device, then all you need to do is discard/forget/lose the key and that’s that. The data will be unrecoverable.

Agreed, which is why it is annoying that since macOS 11 Big Sur, you can’t create a bootable clone by copying to an encrypted drive. You have to first clone to an unencrypted drive (using asr), then boot into it and turn on FileVault. So there’s a window where all your data is un-encrypted, and some of that data may be in pages moved to spare blocks.