How can I permanently delete all personal files on my computer?

Indigo G December 27, 2013
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Hi there

I’m trying to delete all the personal data on a laptop. I did read a lot of things about this on makeuseof.com but I don’t think I fully understood it. Here is what I did:
I copied all the files I want to keep to an external harddisk and then deleted those files(on the laptop) with EgisTec Shredder. Then, I used CCleaner and wiped the free space(49 GB) with 1 pass. Then, I restored the laptop to factory settings. Then I ran CCleaner and wiped the empty disk space(110 GB this time, because of factory settings) again with 3 passes this time. To make sure that no data is recoverable, I downloaded Recuva and it found a lot of(like 17.000) files. I don’t know if it found the files I copied to external hdd, because I can’t go through that much file.

So, what should I do? I tried ‘securely delete checked’ on some files Recuva found but I guess it doesn’t really delete or overwrite them. They’re still there and they look ‘recoverable’. By the way, most of the files’ name are “ZZZ….”, I guess it means that those files are overwritten by CCleaner. Does it mean that if I(or someone) try to recover those ZZ files, it won’t work because it’s already overwritten?

Did I do something wrong with CCleaner settings and it didn’t wiped the entire free space? Or am I using Recuva completely wrong? Like, should I uncheck ‘Deep Scan’?

Sorry for the long message, I tried to explain everything I did. Thanks for any help.

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  1. Paul D Pruitt
    December 31, 2013 at 5:36 am

    Along the lines of Oron J's post...Try http://cmrr.ucsd.edu/people/Hughes/secure-erase.html

    It is supposed to write over once and remove data from clusters that have been set aside as corrupt. So it does more than just overwrite current good sectors, which the other programs do. This feature is built into disk since 2001 but apparently very few pieces of software invoke it.

    Either that or it is an NSA plot to get a piece of software onto a hard drive of someone who really really wants to wipe their disks and thinks they are in the know (someone like me for instance :-) that phones home to the NSA.

    If you are trying to escape the NSA, I think you just can't other than taking out your drive and putting in a new one in your laptop. That's what i would recommend. Take out the drive, put it on a shelf or destroy it. Buy a new drive for the laptop before you sell it.

  2. Oron J
    December 28, 2013 at 3:05 pm

    Just to add that unless your disk is absolutely ancient (pre 2001), there is absolutely no need to overwrite the data more than once. See http://en.wikipedia.org/wiki/Data_erasure#Number_of_overwrites_needed for explanation and relevant references.

  3. Bruce E
    December 27, 2013 at 8:35 pm

    When I only want to whack the stuff that has already been deleted and leave everything else intact, I use Eraser. The standard undelete and several advanced forensic tools have been unable to recover anything from the systems after I have used Eraser. In previous versions of CCleaner, some types of files have been missed and were recoverable (small files stored in the MFT). I have not tried with the most recent versions of CCleaner, so the issue may have been fixed by now.

  4. Alan W
    December 27, 2013 at 5:22 pm

    DBAN nukes your hard disc so that nothing is recoverable. Be careful how you use it!

    http://www.dban.org/

    • Indigo G
      December 28, 2013 at 12:10 am

      Thanks but I can't use DBAN for now. I'll keep it in mind for next time.

  5. Hovsep A
    December 27, 2013 at 2:48 pm

    If the file's allocation had been destroyed or overwritten by other data, there is no possibility to recover this file. Once overwritten, it is not possible to retrieve the information that was originally stored there.

    there are many artifacts left behind after working with clean empty space, in areas that these tools do not address for some reasons. There are a few limitations/exceptions to wiping free space using some software freeware/shareware which is related to the size of a cluster on that file system., for instance the default cluster size for an NTFS volume is 4,096 bytes, this means that every file, regardless of size (excluding NTFS resident files), will get the minimum of 4096 bytes on disk to store data (http://www.ntfs.com/ntfs_optimization.htm)(http://support.microsoft.com/kb/314878). When a user deletes a file a new small file is created and occupies a cluster where there were some artifacts. If the new file is smaller than 4096 bytes and is not wiped using the “wipe free space” option, there could be quite a bit of data left behind in the file slack space that is still accessible to forensic tools. On NTFS file system, clusters are not necessarily allocated for files smaller than the size of a MFT record, but the file is stored completely in the MFT (the file is then said to be resident). If you have insecurely deleted such a small file, the free space on the MFT still may contain the file body and therefore, it must be erased as well.

    Since resident files do not directly occupy clusters ("allocation units"), it is possible for an NTFS volume to contain more files on a volume than there are clusters. For example, a 74.5 GB partition NTFS formats with 19,543,064 clusters of 4 KB. Subtracting system files (a 64 MB log file, a 2,442,888-byte Bitmap file, and about 25 clusters of fixed overhead) leaves 19,526,158 clusters free for files and indices. Since there are four MFT records per cluster, this volume theoretically could hold almost 4 × 19,526,158 = 78,104,632 resident files.
    http://en.wikipedia.org/wiki/NTFS

    NTFS $I30 Index Attributes: Evidence of Deleted and Overwritten Files
    http://computer-forensics.sans.org/blog/2011/09/20/ntfs-i30-index-attributes-evidence-of-deleted-and-overwritten-files#
    Similar to Master File Table (MFT) entries in NTFS, index entries within the B-tree are not completely removed when file deletion occurs. Instead, they are marked as deleted using a corresponding $BITMAP attribute

    under options in CCLeaner
    Options > Settings check box: Wipe Cluster Tips and Wipe MFT Free Space
    Changing CCleaner settings
    http://www.piriform.com/docs/ccleaner/ccleaner-settings/changing-ccleaner-settings
    do note that Wipe Free Space may or will not be able to deal with files locked by the MFT

    Can data cleaned by CCleaner be recovered?
    http://www.piriform.com/docs/ccleaner/introducing-ccleaner/can-data-cleaned-by-ccleaner-be-recovered
    3.For the utmost in security, use Recuva to find files that have already been deleted but still are recoverable, and then securely overwrite them. Be sure to set Recuva to a high number of passes for secure overwriting as well.

    • Indigo G
      December 28, 2013 at 12:21 am

      Wow, that's very detailed. I couldn't understand everything, but thanks. I'll try CCleaner again with checking wipe cluster tips and wipe mft this time.

      By the way, I made a mistake in my original post. When I clicked 'securely delete checked', Recuva did overwrite on some of the files I guess. Because some of them turned from 'excellent' to 'unrecoverable'(green to red). I guess Recuva or other recovery programs can't recover those files any more?

      Anyway, I wiped the free space with CCleaner(3 passes) again yesterday and when I ran Recuva(without deep scan) it didn't find anything. I'm waiting for Deep Scan to finish right now but I guess the files are pretty hard to recover right now, right? Or am I missing something?

      I'm still gonna ran CCleaner one more time with the settings you advised though.

    • Hovsep A
      December 28, 2013 at 2:28 pm

      multiple time can ensure the files are deleted and cant be read even small parts are left, Alan and Bruce gave excellent solutions. if The file was created almost exactly when you ran CCleaner thenCCleaner can't wipe.
      http://www.piriform.com/docs/ccleaner/using-ccleaner/wiping-free-disk-space

  6. dragonmouth
    December 27, 2013 at 1:48 pm

    Seems to me that you have done about as much as you can to make your current files unreadable.

    To me, the easiest and the surest way of "deleting" files that may contain any personal information from your computer is to replace the hard rive with a brand new one and re-install the O/S and apps.

    • Indigo G
      December 28, 2013 at 12:09 am

      Thanks, I feel relieved.

  7. Dalsan M
    December 27, 2013 at 11:36 am

    Darik's Boot and Nuke (DBAN) is what you need to ensure that your data is not recoverable, at least not by most people. http://www.dban.org/ This will thoroughly erase the data from your disk to bits and pieces of unusable data, and then you can format the hard drive, and then reinstall the operating system.

    Trying to clean up anything while you are using an installed operating system will not really clean anything up, only mark the data as usable for replacement with other, newer data. This means that almost anything can potentially be left behind and found through recovery software like Pandora or Recuva.

    • Indigo G
      December 28, 2013 at 12:07 am

      Actually, I was gonna try DBAN but I guess I need to copy the program to a CD and I don't have any right now. Thanks.

  8. Oron J
    December 27, 2013 at 11:08 am

    I think you've done everything right (and in fact, have overdone it...). It's most likely that the cleaners you used delete the files one at a time, changing their names and overwriting their contents. If you are really concerned that there might be some data left over, recover som eof those ZZZ files and examine their contents. My guess is that you'll find them to contain random data.

    The only step you could take beyond what you've already done (other than destroy the hard drive, that is!), would be to image the drive to your external drive, erase the entire disc with DBAN Boot and Nuke and then restore the restore partition to the drive and using it, restore the drive. However, I provided that CCLeaner has done its job, there's really no need for that.

    • Indigo G
      December 28, 2013 at 12:26 am

      I know I'm probably overdoing it :D. But I'm gonna use those programs for other laptops(which I have more personal data) so, I'm trying to get the hang of it.

      Thansk for the advise. But I can't use DBAN right now.

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