Selling personal laptop - dangerous?

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splittermcsplit88
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Selling personal laptop - dangerous?

Postby splittermcsplit88 » Fri Aug 03, 2012 5:37 pm

I got an offer for my personal laptop on craigslist -- local buyer, but is there a way for the buyer to extract deleted files from the computer? I deleted everything including photos, documents, etc, but I feel like he/she might access those files through a different route. I'm not a computer expert at all, so is there way of making sure EVERYTHING is deleted? Should I format and re-install?

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Scotusnerd
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Re: Selling personal laptop - dangerous?

Postby Scotusnerd » Fri Aug 03, 2012 5:43 pm

Long story short, yes there are ways, but they're expensive. Hard drive recovery is a high-tech business. It's generally used for corporate and criminal investigations. You see it in cases where the defendant has something nasty to hide. I read somewhere that the only sure way to make sure something wasn't recoverable was to take out the hard drive and hit it with a hammer until there weren't any pieces left bigger than a quarter.

If you just forget where a file is, though...that's different. He can access that, no problem. If you want everything deleted, you're really going to have to go through and search out everything. Reformatting and reinstalling is probably your best bet, unless you feel competent figuring out where all of your random files are.

09042014
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Re: Selling personal laptop - dangerous?

Postby 09042014 » Fri Aug 03, 2012 5:50 pm

There is software that overwrites the hard drive with random data several times. That makes it untraceable. But you'd have to install windows after.

There might be a program that does that to the empty space on your drive. Google around.

CyLaw
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Re: Selling personal laptop - dangerous?

Postby CyLaw » Fri Aug 03, 2012 5:53 pm

DBAN, then format and reinstall.

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dingbat
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Re: Selling personal laptop - dangerous?

Postby dingbat » Fri Aug 03, 2012 5:53 pm

1) delete every file you don't need
2) reformat your hard drive (optional, but preferred)
3) defragment your drive
4) find a random video file and put it into a compressed file (.zip .rar etc)
5) copy the file a gazillion times, until your hard drive is completely full.
6) delete all copies of said file

Deleting files usually doesn't actually delete the data, just the reference thereto. The data is only deleted when a new file is allocated to that space and overwrites the data. By force-feeding a drive useless files until full, you force it to overwrite every piece of unused data.

edit: didn't know about dban. I assume it works in a similar manner (in that it writes new data to every bit of the hard drive)
Last edited by dingbat on Fri Aug 03, 2012 5:55 pm, edited 1 time in total.

thederangedwang
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Re: Selling personal laptop - dangerous?

Postby thederangedwang » Fri Aug 03, 2012 5:55 pm

theres plenty of free file shredders you can download, use that to delete all your sensitive files, then wipe your HD by reformatting, then reinstalling windows.

If they get anything off of there after that, let them have it, they deserve it.

edit: cylaws program seems cool

CyLaw
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Re: Selling personal laptop - dangerous?

Postby CyLaw » Fri Aug 03, 2012 6:00 pm

dingbat wrote:1) delete every file you don't need
2) reformat your hard drive (optional, but preferred)
3) defragment your drive
4) find a random video file and put it into a compressed file (.zip .rar etc)
5) copy the file a gazillion times, until your hard drive is completely full.
6) delete all copies of said file

Deleting files usually doesn't actually delete the data, just the reference thereto. The data is only deleted when a new file is allocated to that space and overwrites the data. By force-feeding a drive useless files until full, you force it to overwrite every piece of unused data.

edit: didn't know about dban. I assume it works in a similar manner (in that it writes new data to every bit of the hard drive)


This is an interesting method that I may pass on to others when I don't want to take the time of walking them through burning an iso and running dban. Assuming you also do a reinstall of the operating system (which you would want as coders often leave traces with personal information in either the registrary for windows or keychain for os x), the only thing this method does not cover is slack space. But that may be enough for most people to thwart most criminals. I would still DBAN my stuff, personally.

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splittermcsplit88
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Re: Selling personal laptop - dangerous?

Postby splittermcsplit88 » Fri Aug 03, 2012 6:00 pm

Feels so iffy. Is this alrite? http://www.fileshredder.org

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Scotusnerd
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Re: Selling personal laptop - dangerous?

Postby Scotusnerd » Fri Aug 03, 2012 6:01 pm

Google 'Is _____ legit'.

It's worked wonders for me in the past.

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splittermcsplit88
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Re: Selling personal laptop - dangerous?

Postby splittermcsplit88 » Fri Aug 03, 2012 6:02 pm

DBAN looks good too, but why would I need to format and re-install after destroying all that's in my drive?

CyLaw
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Re: Selling personal laptop - dangerous?

Postby CyLaw » Fri Aug 03, 2012 6:04 pm

splittermcsplit88 wrote:DBAN looks good too, but why would I need to format and re-install after destroying all that's in my drive?


Well. You won't need to of course. I just assumed that your wanted to sell the laptop with a functioning copy of windows. DBAN will get rid of everything, including windows. If the buyer is going to install their own OS on there, then just DBAN and call it done.

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splittermcsplit88
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Re: Selling personal laptop - dangerous?

Postby splittermcsplit88 » Fri Aug 03, 2012 6:14 pm

I'm not sure format/re-install is an option though, it's a netbook and there's no cd-rom.

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top30man
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Re: Selling personal laptop - dangerous?

Postby top30man » Fri Aug 03, 2012 6:28 pm

splittermcsplit88 wrote:I'm not sure format/re-install is an option though, it's a netbook and there's no cd-rom.

Virtual drive and a .iso?

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dingbat
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Re: Selling personal laptop - dangerous?

Postby dingbat » Fri Aug 03, 2012 7:16 pm

splittermcsplit88 wrote:I'm not sure format/re-install is an option though, it's a netbook and there's no cd-rom.
Take a look at the steps I outlined. The chance of anything useful still remaining is fairly slim. Repeat the process with a different file (of a different size) if you're paranoid.

(note: as CyLaw pointed out there may be traces of personal information in the registry. I can't recommend mucking around the registry, although that would do the trick; then again, what could possibly be there and who are you selling to that can extract it?)

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kalvano
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Re: Selling personal laptop - dangerous?

Postby kalvano » Fri Aug 03, 2012 9:20 pm

Just DBAN it.

09042014
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Re: Selling personal laptop - dangerous?

Postby 09042014 » Fri Aug 03, 2012 9:29 pm

kalvano wrote:Just DBAN it.

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dingbat
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Re: Selling personal laptop - dangerous?

Postby dingbat » Sat Aug 04, 2012 2:54 pm

splittermcsplit88 wrote:So, I delete everything, defragment, copy+paste useless folders into HD, then delete right? What does the defragmenting do? What about files I have in My Documents?

Basically imagine your hard drive like a set cupboard that can hold books. Generally, you stuff one book in after the other, in order, but you might throw a book away. This creates a gap in between the other books. So, next time there's a book, it'll be put into this gap. Except, if the gap is too small, you split the book in half (or any other fragment you think of) and put one half in one gap, and the other in another gap.
Thing is, when you want to read the book, you need to find both halves, so that takes a bit longer. Now imagine splitting the book into pieces of 1-5 pages. That's what'll end up happening if you never defragment - the gaps keep getting smaller, so the books need to be split into more pieces. That slows drives down a lot.
Defragmenting is when you re-order the books, so that they don't need to be split into fragments. Therefore, your computer no longer slows down.

Defragmenting makes the process I described more efficient and decreases the chance that a small bit of information may get overlooked (imagine a single page slipping through the cracks)

My Documents is a folder on your hard drive, same as any other. It just happens to have an easy shortcut so you can access them right away. If you're looking to delete shit, get rid of the files in my documents too.

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fatduck
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Re: Selling personal laptop - dangerous?

Postby fatduck » Sat Aug 04, 2012 3:10 pm

dd if=/dev/zero of=/dev/sda

BeachedBrit
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Re: Selling personal laptop - dangerous?

Postby BeachedBrit » Thu Aug 16, 2012 9:28 pm

If it's a mac you can just use disk utility. IIRC you can write over the hard drive up to 7 or 9 times that way.

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kalvano
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Re: Selling personal laptop - dangerous?

Postby kalvano » Fri Aug 17, 2012 12:45 am

One pass is sufficient to clear a hard drive. Two of you're determined. Anything more is overkill. After one pass from a good overwrite program (cough DBAN cough), it takes a computer expert to have any hope of maybe, possibly retrieving data. Two full passes and you need a computer forensic specialist, which is ridiculously expensive.

hijodehombre
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Re: Selling personal laptop - dangerous?

Postby hijodehombre » Fri Aug 17, 2012 12:55 am

fatduck wrote:dd if=/dev/zero of=/dev/sda


sudo?

T14hoping
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Re: Selling personal laptop - dangerous?

Postby T14hoping » Fri Aug 17, 2012 2:12 am

CyLaw wrote:DBAN, then format and reinstall.

shock259
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Re: Selling personal laptop - dangerous?

Postby shock259 » Fri Aug 17, 2012 9:36 am

hijodehombre wrote:
fatduck wrote:dd if=/dev/zero of=/dev/sda


sudo?


Image

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pertristis
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Re: Selling personal laptop - dangerous?

Postby pertristis » Sun Aug 19, 2012 3:50 pm

BeachedBrit wrote:If it's a mac you can just use disk utility. IIRC you can write over the hard drive up to 7 or 9 times that way.


This. There are three or so options. One writes over every sector of the drive once; one writes over every sector 7 or 9 times or something; and I believe that one writes over every sector an obscene amount of times. The latter, mind you, also takes an obscene amount of time to complete.

Or, if you're truly worried about someone using your hard drive for ill, buy a new one and put it in there. Then, assuming you don't want to keep the old hard drive, open up the old hard drive, take out the platters, and use a power sander to scrub all the platters.

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lustre_mud
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Re: Selling personal laptop - dangerous?

Postby lustre_mud » Sun Aug 19, 2012 4:35 pm

pertristis wrote:Or, if you're truly worried about someone using your hard drive for ill, buy a new one and put it in there. Then, assuming you don't want to keep the old hard drive, open up the old hard drive, take out the platters, and use a power sander to scrub all the platters.


yep. i do this to my old hard drives. not worth the risk.




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