Old Computer

[GeekMark2]

Hi guys!

I was wondering if you could give me some advice please! I've got an old laptop which works absolutely fine and I was thinking about selling it. Thing is, somebody told me that if I sell it on, people can then access the personal information and files that I had on it..even if I delete them! What's the best way to get rid of all the personal data that was on it before I sell it?

Any advice would be very much appreciated! Thank you

[CPTBadAss]

Reformat the drive? I'm pretty sure that just wipes your drive clean.

[Tym]

If people really want they can almost always get your files back, you can sell it without the hard drive, or reformat it a lot of times (and there is still no guarantee) about 10 times should do it. But this is only if you have classified crap on there. If you are worried about passwords and junk, just reformat it twice.

[SpAmRaY]

http://www.dban.org/

[Parak]

Reformat the drive? I'm pretty sure that just wipes your drive clean.

If people really want they can almost always get your files back, you can sell it without the hard drive, or reformat it a lot of times (and there is still no guarantee) about 10 times should do it. But this is only if you have classified crap on their. If you are worried about passwords and junk, just reformat it twice.

Mind, there's no real world demonstrable and repeatable proof that data is recoverable from hard drives that had a single pass overwrite with zeroes. The only claim to that is a 1996 paper that has been debunked a number of times.

[fohat.digs]

Reformatting and deleting the partition should make it safe for just about any resale. There is just not enough value to somebody (unless they know that you are very rich) to make it worthwhile to expend the effort.

You can also clean out everything but the OS, and set a video camera to run continuously until it fills up the disk with video of the furniture and wall.

Also, you can re-partition and format to another OS, such as installing Linux on a Windows 7 drive.

Nobody would bother to try to sift through all that.

[GeekMark2]

Thanks for the replies guys!

I think that reformatting the hard drive is probably the option for me, is that basically just running the discs that came with the laptop when I bought it?

No mega secret information on it really, it's just that I don't like the thought of somebody having access to my personal info 

[alosec]

Reformatting the harddrive is like putting a chain with a padlock over a cooler on tailgating day: people can still access the cooler if they really really wanted to, but most people aren't going to go to that length for some free ****ty beer.

You're basically just keeping honest people honest.

[rowdy]

Replace the hard drive - the only way to be sure.

Or just nuke it from orbit.

[SpAmRaY]

The only way to really do it right is to put a drillbit right through the platter.

[rowdy]

Depends if he is willing to remove the HDD from the laptop in the first place, in which case he might as well keep it and use it for something else.

[Halvar]

Many people take this lightly, and it indeed was less of a problem years ago when most people didn't have sensitive data on the drives.
 
It's actually very easy to recover most of the data from a drive that was merely formatted. You download a free data recovery program, you run it, and you get back most of the files that were there before the formatting. And trust me, more people than you'd think do this when they bought a used computer, just out of curiosity.

If there is anything on your HD that other people could be interested in and could pose a problem for you (ebay, paypal, banking passwords saved in the browser, documents, whatever) then do yourself a favor and use a data descruction software on the hard drive before you sell it (it's free, just takes some time to run).

http://pcsupport.about.com/od/toolsofthetrade/tp/erase-hard-drive.htm

[Leslieann]

That true to some extent Halvar, but it's not quite that straightforward.

In this case the OP also planned to re-install the original operating system on it. This would wipe out TONS and TONS of data. Yes, if you just format and recover, you can get a lot back, but as soon as you start adding data over the top, recoverable data begins dropping extremely fast. The more fragmented the drive was prior to being formatted also has a huge impact on how much you can recover (without investing a ton in software and time). Which means the older the system, the less data you will get. 

Just reinstalling the OS over a formatted drive is enough to destroy most of it.
What are the odds you will get someone who even bothers to look?
Of that percentage, what are the odds they will actually find an actual working card, expiration date and security code?

Yes, it's playing the odds, but the truth is, you put your card number at far higher risk just by using it every day.

[rowdy]

I still say the only way to be 100% absolutely sure is to replace the drive and keep the old one yourself.

[Halvar]

If you wipe out an HD and reinstall the OS, chances are that OS will use roughly the same part of the disk that it used before when it was first installed, because the OS begins to use an empty HD in a certain order. And the OS itself uses only a small part of the HD if the HD is large enough.

The chance to be able to reconstruct small documents like JPEGS or DOCX or most kinds of stuff that you create yourself is still quite high afterwards. Sure, it's a risk that everyone has to assess for himself. I also don't think that you need to overwrite data seven times or anything like that -- the risk that the new user will give the disk to a professional data reconstruction lab that takes it apart is near zero -- but I think it's worth it to protect yourself from easy-to-use "undelete" software by overwriting everything once. Which formatting alone doesn't do.

[rowdy]

Forensically, with the right equipment, it is possible to retrieve information from a hard drive even if it has been zeroed out several times.  This is extremely expensive, but depending on what information is on it and how badly someone wanted to access it, it would be possible - to a certain extent.

Reinstalling or writing something random over the top might make the process slightly more difficult, but may still be possible depending on the above factors.

[microsoft windows]

FIRST OFF, ARE YOU SURE THAT SOMEBODY'S GOING TO BUY YOUR OLD COMPUTER? IF IT'S GOT LESS THAN A CORE 2 DUO FOR A CPU, YOU PROBABLY AREN'T GOING TO GET MORE THAN $30 FOR IT. SOMETIMES IT MIGHT JUST BE EASIER TO GIVE THESE THINGS AWAY TO A FRIEND OR FAMILY MEMBER.

[Leslieann]

If you wipe out an HD and reinstall the OS, chances are that OS will use roughly the same part of the disk that it used before when it was first installed, because the OS begins to use an empty HD in a certain order. And the OS itself uses only a small part of the HD if the HD is large enough.

The chance to be able to reconstruct small documents like JPEGS or DOCX or most kinds of stuff that you create yourself is still quite high afterwards. Sure, it's a risk that everyone has to assess for himself. I also don't think that you need to overwrite data seven times or anything like that -- the risk that the new user will give the disk to a professional data reconstruction lab that takes it apart is near zero -- but I think it's worth it to protect yourself from easy-to-use "undelete" software by overwriting everything once. Which formatting alone doesn't do.

True, but again, only to some extent.
Windows gets updates, which alters a lot of files. Windows XP was 500 megs, by the time you install SP3, it's 1.5 gigs and only about 200 megs of it is original files. It also installs fragmented, which only gets worse. All data tends to cluster to the inner sectors on a drive, which is why Windows tends to occupy the same space every time, but so does all of the other data and it doesn't all go back to the same exact spot. The older the previous install was, the worse the fragmentation will be (even if they used Windows Defrag), while Win7 does better, Win Xp was notorious for fragmenting and decreasing performance, sometimes in as little as 3 months.

It only takes one cluster to be damaged and most people (and software) will give up, some can't even string together split fragmented clusters. While you think picture are small, they occupy a lot of clusters, each cluster ups the odds of a picture being partially over-written. On 4k cluster Windows 7 install, a 1 meg picture has 250 clusters, that's 249 chances for fragmentation for a simple 1 meg file.

In my experience, you can recover close to everything if it was formatted and left alone, you can recover nearly all of it. Fragmentation can be a headache depending on the software used. Just deleting files (and emptying the recycle bin) and use the computer for a month will destroy a surprising amount of data. I had to do this the other day for a customer, we only recovered 5% of her pictures after 3 hours of work. If it was formatted then reinstalled, my experience has been you will be lucky to get 5% of files working with readily pirated software, and even then, 200gigs can take a whole night to process, much less sort through. Even zeroing out a drive these days takes a VERY long time because drives are so big.

[smknjoe]

http://www.dban.org/

SpamRay got it right. There are a couple of DoD and other compliant wipes in there. They also offer "certified" compliant software that you can pay for. Done!

[Halvar]

It only takes one cluster to be damaged and most people (and software) will give up, some can't even string together split fragmented clusters. While you think picture are small, they occupy a lot of clusters, each cluster ups the odds of a picture being partially over-written. On 4k cluster Windows 7 install, a 1 meg picture has 250 clusters, that's 249 chances for fragmentation for a simple 1 meg file.

That's a true but very misleading statement (true but only to some extent you could say...    ). OSes try hard to place files on the HD in a way that avoids fragmentation, and if the HD is not too full, they succeed in the huge majority of cases, especially for small files. Typical fragmentation percentages on systems that have a defragmenter running in the background like Windows from Vista on are in the <3% range, which means that >97% of files are stored contiguously.

If it was formatted then reinstalled, my experience has been you will be lucky to get 5% of files working with readily pirated software, and even then, 200gigs can take a whole night to process, much less sort through. Even zeroing out a drive these days takes a VERY long time because drives are so big.

The percentage will highly depend on the OS, the age of the installation, the percentage of space used on the drive and the size of data files. If you had a separate data partition like many people do, it might even be 90%...

You're right (to the full extent!) that all this takes a lot of time on modern drives, but running a data destruction program only takes computing time, you don't have to babysit.

Everyone has to decide on this himself. But I guess we all tend to downplay risks to essentially comfort the inner lazybone in all of us, and whenever that works out by sheer luck (which it will in most cases), our assessment will be skewed even more the next time...

[fohat.digs]

Hard drives have some really good magnets in them.

But I still haven't figured out how to get them off without damaging the plating 90% of the time.

[Leslieann]

That's a true but very misleading statement (true but only to some extent you could say...    ). OSes try hard to place files on the HD in a way that avoids fragmentation, and if the HD is not too full, they succeed in the huge majority of cases, especially for small files. Typical fragmentation percentages on systems that have a defragmenter running in the background like Windows from Vista on are in the <3% range, which means that >97% of files are stored contiguously.

Do an Xp, Vista or Win7 install then fire up Defraggler, you will be surprised just how much fragmentation there actually is right from the start, especially after installing updates.

I always thought they would just line up the files, but nope.

[rowdy]

Hard drives have some really good magnets in them.

But I still haven't figured out how to get them off without damaging the plating 90% of the time.

I pulled two out of a huge old Digital HDD - once they clamp on to something it's hard to get them off.

I have two.

They are currently stuck together.

Haven't been able to separate them yet.

[tipo33]

http://www.dban.org/

SpamRay got it right. There are a couple of DoD and other compliant wipes in there. They also offer "certified" compliant software that you can pay for. Done!

I duno, since the whole NSA thing, I'm starting to be wary of "DoD compliant"   Might as well say "Has a backdoor"

[smknjoe]

http://www.dban.org/

SpamRay got it right. There are a couple of DoD and other compliant wipes in there. They also offer "certified" compliant software that you can pay for. Done!

I duno, since the whole NSA thing, I'm starting to be wary of "DoD compliant"   Might as well say "Has a backdoor"

LOL, that's funny! The whole NSA thing is nothing new. It's been going since the 60's starting with illegal phone taps. Compliant doesn't mean it was produced by the DoD it means it's an approved method for wiping DoD drives.

[PointyFox]

I've recovered things from hard drives overwritten 3 times, but mostly things like text or picture fragments. 

[smknjoe]

I've recovered things from hard drives overwritten 3 times, but mostly things like text or picture fragments. 

...as in re-installing the OS a few times? Sure. Not after using a mid-grade wipe with DBAN.