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southrncomfortjm
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Safest way to prep a laptop for sale

Sun Jul 16, 2017 12:29 pm

Hey all,

I have a Dell Laptop with SSD that I want to sell. Basically, I had it for gaming when I travelled, but since I have a Switch now, the laptop just isn't as appealing on the go.

What's the best way to clear/reformat/whatever the SSD for resale? Can I secure erase it and then put a new windows install on it and be safe knowing my old info shouldn't be recoverable?

Thanks!
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Re: Safest way to prep a laptop for sale

Sun Jul 16, 2017 2:05 pm

That's a pretty nice laptop...if I wasn't being a stickler for enterprise grade I might be sending a PM right about now.

SSDs can generally be erased via a software command to nuke itself. If you know the manufacturer of the drive, you should be able to use their SSD management tool to do it. Otherwise you may need to do some digging. I suppose you could run a single-pass DBAN or dd some random data onto it (SSDs don't have 'memory' like HDDs do), but doing that will add wear to the drive. Door number three is of course to just swap out the SSD for a different one, and recoup most of the cost in the sale. As a prospective buyer I'd be looking to upgrade to a 480GB anyway, though my preference for mobile workstations would suggest that my needs are quite different than the typical notebook user.
 
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Re: Safest way to prep a laptop for sale

Sun Jul 16, 2017 2:14 pm

If you do a Reset My PC with newer versions of Win 10, one of the options says it will fully clean drives for re-sale.(only two options)
 
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Re: Safest way to prep a laptop for sale

Sun Jul 16, 2017 6:16 pm

Image
 
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 5:37 am

Yeah, using the drive's "secure erase" capability followed by an OS reinstall should be sufficient. If you're really paranoid, you can do a full overwrite first, then use the drive's "secure erase".

A truly determined attacker with knowledge of the internal workings of the firmware and sophisticated forensic equipment might still be able to get something off the drive, but you're talking TLA-level (domestic or foreign) capability and budget.
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southrncomfortjm
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 4:19 pm

Awesome. Thanks everyone.
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 7:06 pm

I never got the idea of multi-pass erasing. If old data can be read after being overwritten, why don't HDD manufacturers use that to double or triple the capacity? :)
 
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 7:19 pm

AIUI if you write one pass of zeroes to spinning rust, in theory with an electron microscope you could infer the magnets' previous states. Seems to me that the one pass of garbage would be proof against anyone without those kind of resources. If you've made that sort of enemy, 7 passes of random data on spinning rust or one of the SSD's secure-erase routine should be quite enough.

Don't ever do the 35-pass "Gutmann" erasure. Firstly, it's stupid overkill. Secondly, that suite is a collection of patterns optimized for scrambling data from old hard drives using long-obsolete encoding methods (Modified Frequency Modulation and Run Length Limited), and even if you have one of those you're supposed to pick the appropriate patterns for your disk and controller. Anyone advocating for the thing is an ignoramus and you shouldn't believe a word they say about data security.
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 7:53 pm

meerkt wrote:
I never got the idea of multi-pass erasing. If old data can be read after being overwritten, why don't HDD manufacturers use that to double or triple the capacity? :)

Because recovering that data is *incredibly* slow and expensive. :P

I don't even get the option of a DoD or NSA approved erase...I get to degauss, crush, and shred up our old drives at work. I wish I could say I get to do that myself occasionally but they won't let me play with the shredder. :(
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 8:38 pm

Waco wrote:
I don't even get the option of a DoD or NSA approved erase...I get to degauss, crush, and shred up our old drives at work. I wish I could say I get to do that myself occasionally but they won't let me play with the shredder. :(

Now that the platters are glass, it's even easier. Three or four passes with a carbide-tip 1/4 drill through the entire drive casing in the platter area will so shatter the platters as to make shredding mere excess (except for TLAs and your DoE case).
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 8:58 pm

meerkt wrote:
I never got the idea of multi-pass erasing. If old data can be read after being overwritten, why don't HDD manufacturers use that to double or triple the capacity? :)

Not really the same thing, but SMR drives actually *do* partially erase previous valid data with new data: https://en.wikipedia.org/wiki/Shingled_ ... _recording

Waco wrote:
I don't even get the option of a DoD or NSA approved erase...I get to degauss, crush, and shred up our old drives at work. I wish I could say I get to do that myself occasionally but they won't let me play with the shredder. :(

The extreme erasure methods are so that you don't need to physically destroy the drive (and can potentially re-use it).
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 9:02 pm

just brew it! wrote:
Waco wrote:
I don't even get the option of a DoD or NSA approved erase...I get to degauss, crush, and shred up our old drives at work. I wish I could say I get to do that myself occasionally but they won't let me play with the shredder. :(
The extreme erasure methods are so that you don't need to physically destroy the drive (and can potentially re-use it).

Based on Waco's stated location, I understand why reuse isn't an option. Even my 2-bit State regulatory operation drills every spinning drive upon decom. Since we're too cheap to buy SSDs for laptops, I doubt they've even thought of proper (and easy) destruction methods for same.
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 9:10 pm

Captain Ned wrote:
Based on Waco's stated location, I understand why reuse isn't an option. Even my 2-bit State regulatory operation drills every spinning drive upon decom. Since we're too cheap to buy SSDs for laptops, I doubt they've even thought of proper (and easy) destruction methods for same.

I imagine it'll probably involve removing the PCB and drilling a hole through each flash chip.
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 9:54 pm

just brew it! wrote:
Not really the same thing, but SMR drives actually *do* partially erase previous valid data with new data: https://en.wikipedia.org/wiki/Shingled_ ... _recording


Yep. They're a total PIA to deal with, but if you design your storage stack carefully they are a godsend in terms of cost/bit stored. If your workload is bad for them, though, god help you. Enjoy your handful of IOPs per drive...

just brew it! wrote:
The extreme erasure methods are so that you don't need to physically destroy the drive (and can potentially re-use it).

I would love for our policies to change so I could move old hardware and/or salvage it. I'd love to have 100 PiB of drives that I could re-use for unclassified projects once they're old and worn out. Build a bit of extra redundancy into the system and they'd be amazing for the low low cost of free.

Captain Ned wrote:
Based on Waco's stated location, I understand why reuse isn't an option. Even my 2-bit State regulatory operation drills every spinning drive upon decom. Since we're too cheap to buy SSDs for laptops, I doubt they've even thought of proper (and easy) destruction methods for same.

I'd be pretty happy to just crush the drives...glass platters simply don't leave much when they shatter. :)
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 10:10 pm

Waco wrote:
I'd be pretty happy to just crush the drives...glass platters simply don't leave much when they shatter. :)

It's why drilling is so easy. They're tempered glass, so the first crack and the whole thing shatters. Besides, a coil that can properly degauss modern hard drives is either part of your daily work or shouldn't be anywhere near said work.

A sad data destruction story: A co-worker of mine passed away roughly around 16 years ago (lung cancer). His widow contacted the Department to ask us when we would be over to remove all of his accumulated "office" stuff from the house. When the hoard was returned to my office we discovered roughly 1,500 3.5" floppies covering some 15 years of work. As this was before the advent of media shredding devices/vendors, the entire office staff spent a couple of weeks (in our "spare" time) ripping off the sliding shield, popping open the case, pulling the disc, and popping out the metal drive hub so that we could put just the magnetic media in our paper-based shred bins (we'd called the shredding vendor and that's all they wanted in the bins). We all spent the next 2 weeks nursing all sorts of cuts/abrasions to fingers caused mainly by prying off the sliding shield.
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Re: Safest way to prep a laptop for sale

Mon Jul 17, 2017 10:11 pm

Waco wrote:
I don't even get the option of a DoD or NSA approved erase...I get to degauss, crush, and shred up our old drives at work. I wish I could say I get to do that myself occasionally but they won't let me play with the shredder. :(


I'd note that as of like 2007 DoD 5220 no longer accepts multi-pass erasure (DBAN for example) as a valid method of data destruction.

I'd note that Windows does have a way to write all zeroes to a drive.

diskpart <enter>
select disk <#> <enter>
clean all

Some modern UEFI also include the ability.
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Re: Safest way to prep a laptop for sale

Tue Jul 18, 2017 6:33 am

Waco wrote:
Not really the same thing, but SMR drives actually *do* partially erase previous valid data with new data: https://en.wikipedia.org/wiki/Shingled_ ... _recording

Yep. They're a total PIA to deal with, but if you design your storage stack carefully they are a godsend in terms of cost/bit stored. If your workload is bad for them, though, god help you. Enjoy your handful of IOPs per drive...

Indeed. I get to deal with them (both the drive-managed and host-managed variety) at my day job now. They present some "interesting" challenges.

Captain Ned wrote:
A sad data destruction story: A co-worker of mine passed away roughly around 16 years ago (lung cancer). His widow contacted the Department to ask us when we would be over to remove all of his accumulated "office" stuff from the house. When the hoard was returned to my office we discovered roughly 1,500 3.5" floppies covering some 15 years of work. As this was before the advent of media shredding devices/vendors, the entire office staff spent a couple of weeks (in our "spare" time) ripping off the sliding shield, popping open the case, pulling the disc, and popping out the metal drive hub so that we could put just the magnetic media in our paper-based shred bins (we'd called the shredding vendor and that's all they wanted in the bins). We all spent the next 2 weeks nursing all sorts of cuts/abrasions to fingers caused mainly by prying off the sliding shield.

FWIW the magnetic coatings on floppy disks have really low coercivity by modern standards. I have an old hand-held Radio Shack reel-to-reel tape bulk eraser (from the '70s?) which seems to do a good job of erasing floppies. Near as I can tell (I haven't tried to open it up) it is just an electromagnet wired directly to the mains, using the 60Hz alternating field to scramble the bits on the media.

Ryu Connor wrote:
I'd note that as of like 2007 DoD 5220 no longer accepts multi-pass erasure (DBAN for example) as a valid method of data destruction.

Well, that would explain why everyone seems to go with physical destruction. I was aware that DoD did not consider multiple erasure to be a valid method of destroying sensitive data on flash media; probably easier to just make a blanket rule for all media. It's still going to render the data unrecoverable except by sophisticated forensics; but for obvious reasons, the DoD needs to concern themselves with sophisticated forensics!

At the defense contractor I worked at until a couple of years ago, the rule was that any data storage devices had to be removed from equipment that was being scrapped. The drives were handed over to IT to deal with. (We did not handle Secret or Top Secret information at our facility, but there were still ITAR-restricted documents, trade secrets, sensitive employee records, etc.)
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southrncomfortjm
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Re: Safest way to prep a laptop for sale

Tue Jul 18, 2017 8:17 am

I love how this thread has simultaneous gone completely off topic, but remained completely interesting and relevant at the same time.
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Re: Safest way to prep a laptop for sale

Tue Jul 18, 2017 8:39 am

Waco wrote:
meerkt wrote:
I never got the idea of multi-pass erasing. If old data can be read after being overwritten, why don't HDD manufacturers use that to double or triple the capacity? :)

Because recovering that data is *incredibly* slow and expensive. :P

So how about that:
Let's assume data overwritten once reads at .1 speed, and overwritten twice at .01. Seems fine for nearline and offline backup? :)

just brew it! wrote:
Not really the same thing, but SMR drives actually *do* partially erase previous valid data with new data
Sure. But you can't read it back.
 
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Re: Safest way to prep a laptop for sale

Tue Jul 18, 2017 8:55 am

meerkt wrote:
Waco wrote:
meerkt wrote:
I never got the idea of multi-pass erasing. If old data can be read after being overwritten, why don't HDD manufacturers use that to double or triple the capacity? :)

Because recovering that data is *incredibly* slow and expensive. :P

So how about that:
Let's assume data overwritten once reads at .1 speed, and overwritten twice at .01. Seems fine for nearline and offline backup? :)

You're probably looking at more like .001 and .000001, and that's after replacing the electronics (and maybe the heads too) with super-secret TLA stuff.

just brew it! wrote:
Not really the same thing, but SMR drives actually *do* partially erase previous valid data with new data

Sure. But you can't read it back.

The whole point of SMR is that you *can* read back partially overwritten tracks. They leave just enough of the previous track to recover the data (and the next track gets completely obliterated).

And I did preface it with "not really the same thing". :wink:
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Re: Safest way to prep a laptop for sale

Tue Jul 18, 2017 10:09 am

There was a challenge back in 2008 to recover a hard drive that had been overwritten with a "dd" of zeros. None of the commercial data recovery firms were willing to take it on. We wouldn't know if any of the spy agencies were capable of doing it.

Shingled recording isn't exactly overwriting the same track, the read head is narrow enough that it reads non-overlapping tracks. The problem is the write head has to be bigger and that causes the tracks to overlap like shingles on a house roof, hence the name.

Modern drives tend to have firmware and parameters on a track that's only readable by the drive and not by the host. If you use a bulk eraser on them then you have likely erased that and the drive is useless.

If you are not under any secret restricitions or anything, just use the ATA Secure Erase command and consider yourself good to go. If the drive is too old to implement Secure Erase then one pass of writing zeros is enough, the rest is just theoretical.
 
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Re: Safest way to prep a laptop for sale

Tue Jul 18, 2017 10:19 am

notfred wrote:
Modern drives tend to have firmware and parameters on a track that's only readable by the drive and not by the host. If you use a bulk eraser on them then you have likely erased that and the drive is useless.

Given the high coercivity of modern media, you need a fairly powerful magnet to degauss recent drives. I'm pretty sure my antique bulk tape eraser would have no effect (maybe I'll try it sometime on a drive I'm planning on junking, just for grins).
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Re: Safest way to prep a laptop for sale

Tue Jul 18, 2017 11:00 am

Captain Ned wrote:
Three or four passes with a carbide-tip 1/4 drill through the entire drive casing in the platter area will so shatter the platters as to make shredding mere excess

A standard black oxide bit will do the job perfectly fine. :wink:
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Re: Safest way to prep a laptop for sale

Tue Jul 18, 2017 1:26 pm

just brew it! wrote:
notfred wrote:
Modern drives tend to have firmware and parameters on a track that's only readable by the drive and not by the host. If you use a bulk eraser on them then you have likely erased that and the drive is useless.

Given the high coercivity of modern media, you need a fairly powerful magnet to degauss recent drives. I'm pretty sure my antique bulk tape eraser would have no effect (maybe I'll try it sometime on a drive I'm planning on junking, just for grins).

I've tried and failed to get a field strength rating for erasing modern drives, so I'd guess it's *way* up there.

As for reading a drive that's been written with zeros (once). If it's a modern non-SMR drive it isn't all that difficult provided you have the right tools - biasing the heads slightly off-track will recover quite a bit.
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Re: Safest way to prep a laptop for sale

Mon Aug 28, 2017 8:49 am

hi southrncomfortjm,
Are you still interested to sell your Pc? One of my friends is interested to buy
 
southrncomfortjm
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Re: Safest way to prep a laptop for sale

Mon Aug 28, 2017 9:22 am

Onlyzen wrote:
hi southrncomfortjm,
Are you still interested to sell your Pc? One of my friends is interested to buy


Already sold!
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