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1863 posts

Uber Geek

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# 207641 6-Jan-2017 12:47
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Hi guys,

 

 

 

I'm going to sell my desktop computer on trademe and will format the hard drive, but is there a safer way to ensure data cant be recovered? I understand even after formatting, the data may still be there?

 

 

 

Cheers,


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8753 posts

Uber Geek

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  # 1699319 6-Jan-2017 12:50
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are you selling it with an OS? or just an empty HDD?


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Microsoft

  # 1699322 6-Jan-2017 12:52
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Do you want to sell the hard drive too? Otherwise drill holes thru the HDD platters and chuck it into your nearest steel smelter

 
 
 
 




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Uber Geek

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  # 1699328 6-Jan-2017 13:09
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I'm selling the desktop PC... with everything (yes including the hard drive) :)


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Master Geek


  # 1699330 6-Jan-2017 13:10
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Depends on how paranoid you are me how sensitive the data on the drive is.

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Master Geek


  # 1699332 6-Jan-2017 13:16
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You could run DBAN followed by one or two ATA Secure Erase operations on the drive just to be sure. That would stop anyone reading the data from the drive with it just plugged into a computer as normal. Should go a decent way to stopping anyone recovering it using other methods as well. Then again, if you're hiding from the NSA, you'd be best to do that, open the drive, remove the platters then melt them. It all depends on your level of paranoia.



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  # 1699340 6-Jan-2017 13:28
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It's only family photos and videos ect so i doubt anyone would be interested in seeing them anyway.

 

 

 

Surely if i format the hard drive, then fill all the hard drive space with blank files, then delete all the blank files, then all previous data would be gone? Logically this seems right? If the hard drive is completely over ridden with new files, how could the old files physically still be available as there would be no space for them?

 

 

 

 


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Ultimate Geek


  # 1699342 6-Jan-2017 13:31
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DBAN is a good option, you download the image and create a boostable cd/usb etc and follow the onscreen instructions


 
 
 
 


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Master Geek


  # 1699343 6-Jan-2017 13:37
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loceff13:

DBAN is a good option, you download the image and create a boostable cd/usb etc and follow the onscreen instructions



Probably the best option. Just boot it up and it overwrites the entire disk with random data a couple of times then zeros the drive out.

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  # 1699368 6-Jan-2017 13:45
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I just boot Debian off a live CD image (on a usb stick), then just good old dd.


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Ultimate Geek


  # 1699372 6-Jan-2017 13:53
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https://www.youtube.com/watch?v=8yC1zwFiiyg


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Ultimate Geek


  # 1699404 6-Jan-2017 14:18

DBAN is great.

Use the NSA method basically it rights zeros and ones and then does it again and again depending on the number of passes. I normally do 4+ passes.

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Master Geek


  # 1700644 9-Jan-2017 20:33
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NSA level wipes are just paranoia unless you are a person of interest to three letter agencies.

 

If you do not want to wipe and do a fresh install but are prepared to hunt down and delete all the files you want gone a useful tool is the command 'cipher' run from an administrator cmd.exe window.

 

This tool has an option to wipe data from deallocated space on the disc. It is installed on my Windows 10 box.

 

Microsoft Technet article;

 

https://technet.microsoft.com/en-us/library/bb490878.aspx





Obsequious hypocrite

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Ultimate Geek


  # 1703335 14-Jan-2017 23:47
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simon14:

 

It's only family photos and videos ect so i doubt anyone would be interested in seeing them anyway.

 

 

 

Surely if i format the hard drive, then fill all the hard drive space with blank files, then delete all the blank files, then all previous data would be gone? Logically this seems right? If the hard drive is completely over ridden with new files, how could the old files physically still be available as there would be no space for them?

 

 

 

 

 

 

That is mostly secure against some random punter using a standard OS and software but it is not close to secure using the tools available for drive analysis.

 

The problem arises because when you write your new data to the disk, you are writing it on top of what was there before. That means that, if you write 12345 to a part of the disk, you will always read back 12345. If you look hard at the analogue signal coming off the disk's read head, you can tell that the data last written was 12345 but that before this, the disk held the data abcde. So far as I am aware, the state of the art is to be able to go back to see the last four sets of data that were written to a drive if the data was truly random. If the data was not truly random then you might be able to go back further. That is why so called secure erase will write true random data five or more times.*

 

Do you need to worry about this? Such analysis of disk data is expensive and requires skilled staff and considerable time for analysis. I doubt that the FBI did this to KDC's hard drives but I bet that the NSA did it to the hard drives that they recovered from OBL's compound in Abbotabad. You are most likely safe from this threat.

 

Even flash drives are susceptible. It is a lot harder and more expensive but I have seen people operating tech that would tell you what data was in a flash cell before it was erased and rewritten. I doubt that even the NSA will use such tech other than to prove that they can do it in case they ever come up against a target that makes it worthwhile.

 

[* Another way to think about this is to consider a whiteboard. I can write something on a whiteboard and you can sit in my audience and read the what I have written. I can then rub it out with a cloth and write something new and you can sit there and see what I have written now. If you sneak up to the board at the end of the second presentation, you can have a close look and you will most likely see what was written the first time and perhaps the time before that as the erase process is not perfect.]


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  # 1703356 15-Jan-2017 08:20
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Eraser, works from windows.


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