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How secure is merely discarding (TRIMing) all of a SSD's blocks?

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Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#11

Post by bshipp »

fdeee wrote: post #7
h506001 wrote: post #3

Super interested in this and would love to hear about some techniques. Used to work at a HealthTech co. We had an “appliance” that we’d send to doctor offices to integrate with other diagnostic machines on the network. Sometimes we would send out new ones to replace the old. When we got the old ones back, it was always unclear how to purge and recommission SSD/NVME drives. My best attempt was using GNU shred, but it…

The only proper way of disposal is physical destruction, preferrably on site and under observation of inhouse staff. There are contractors you can hire in those: https://shredsupply.com/hard-drive-shredding-trucks/ (no relation, just arbitrary google hit). I'm also unsure as to why you are getting drives back at all, any of your customers should not have any kinds of storage devices leave their site intact. At least…

Shredding/sledgehammer is likely the best option for secure disposal of mechanical drives, but SSDs are a different animal and are likely reusable given some of the suggestions in this thread.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#12

Post by LinuxBender »

As others have mentioned, use encryption. But that has gaps as someone can hold onto the drive and wait for impossible to break to become somewhat expensive to break to broke by mistake through bad encryption implementation.

Put the encrypted drive into a hydraulic press and flatten it into a thin sheet, then run that sheet through a chop saw, or just use tin-snips if your hydraulic press was powerful enough. A hydraulic press and a chop saw are a few hundred bucks whereas drive shredders can range from $30k to $200k.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#13

Post by wyager »

generalizations wrote: post #5

Or you encrypt the entire drive. Then the secure erasure is a matter of throwing away the keys, and you don't have to bother with thinking through your threat model.

Two issues with that - you have to make sure you dispose of the key(s), and this doesn't let you securely erase just part of the drive.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#14

Post by fdeee »

jsiepkes wrote: post #2

> Flash storage, unlike traditional hard drives, can really be completely and irrecoverably erased, with no lingering magnetic ghosts that a sufficiently determined person could in theory reconstruct. I think people vastly overestimate the possibility to recover any data from a wiped HDD. See for example this article by SANS [1]. To recover a single bit you have a better chance of flipping a coin to see if the bit wa…

I think you are right in that it is quite impossible to read data that has been overwritten from a sufficiently modern HDD.

But all modern HDDs retire sectors that exhibit a higher correctable error rate and replace them by reserve sectors. Those retired sectors then still contain readable data (maybe with some bit errors) if you know the appropriate factory mode commands. Overwriting the entire disk also won't overwrite retired sectors, except if the disk has an explicit function for it and you trust that function to work properly.

In short, you always need full disk encryption.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#15

Post by detrites »

germanier wrote: post #8
jsiepkes wrote: post #2

> Flash storage, unlike traditional hard drives, can really be completely and irrecoverably erased, with no lingering magnetic ghosts that a sufficiently determined person could in theory reconstruct. I think people vastly overestimate the possibility to recover any data from a wiped HDD. See for example this article by SANS [1]. To recover a single bit you have a better chance of flipping a coin to see if the bit wa…

This can't be true. Any method must be at least as good as a coin toss. If it's worse you can just bit flip the result and end up better than the coin.

Unbelievably, the paper actually makes that claim:

> That is, if you toss a coin, you have a 50% chance of correctly choosing the value. In many instances, using a MFM to determine the prior value written to the hard drive was less successful than a simple coin toss.

More believably, the paper was written by Dr Craig Wright.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#16

Post by Nursie »

h506001 wrote: post #3

Super interested in this and would love to hear about some techniques. Used to work at a HealthTech co. We had an “appliance” that we’d send to doctor offices to integrate with other diagnostic machines on the network. Sometimes we would send out new ones to replace the old. When we got the old ones back, it was always unclear how to purge and recommission SSD/NVME drives. My best attempt was using GNU shred, but it…

Buy SSDs with secure erase (many of them!), they encrypt data internally. Secure-erase the throws away the key, and all the data is now irretrievable.

Job done…

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#17

Post by scns »

h506001 wrote: post #3

Super interested in this and would love to hear about some techniques. Used to work at a HealthTech co. We had an “appliance” that we’d send to doctor offices to integrate with other diagnostic machines on the network. Sometimes we would send out new ones to replace the old. When we got the old ones back, it was always unclear how to purge and recommission SSD/NVME drives. My best attempt was using GNU shred, but it…

https://news.ycombinator.com/item?id=35069622

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#18

Post by katdork »

The absurdity here that you can't do it because your BIOS won't let you, hdparm can do this! You can literally just boot a Live USB!

https://wiki.archlinux.org/title/Solid_state_drive/Memory_ce...

And anyone who thought TRIM would be a reliable way to get rid of data to begin with didn't have an understanding of TRIM!

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#19

Post by [deleted] »

jsiepkes wrote: post #2

> Flash storage, unlike traditional hard drives, can really be completely and irrecoverably erased, with no lingering magnetic ghosts that a sufficiently determined person could in theory reconstruct. I think people vastly overestimate the possibility to recover any data from a wiped HDD. See for example this article by SANS [1]. To recover a single bit you have a better chance of flipping a coin to see if the bit wa…

[deleted]
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