How to erase file information on unused disk space

We all know that it is important to securely delete all files on a hard drive before giving it to someone else, for instance by selling it on eBay or giving your computer to a family member or friend, or even trashing it. This holds especially true if you plan on selling the hard drive on Internet sites such as eBay. I know that some users buy used hard drives on eBay purely for the thrill of trying to recover data that was deleted on those drive. This could get you in a world of trouble if you think of the private information that you save on your computer.

I was thinking of something different though. What if I want to keep my hard drives for now but make sure that deleted data can't be recovered by any means? I tried and ran some file recovery programs such as Recuva and it showed thousands of files that were still referenced on my system although they have been deleted before. I think that this is a privacy problem and decided to look for a way to delete all file information on the unused part of all of my hard drives connected to the PC.

I decided to use Recuva first and see how many file information it would find. After that I would run a program named Eraser which I will use to clean the unused disk space of any deleted file information and finally run Recuva again to see if this reduced the amount of files that it would be able to restore from the drives.

Testing my Hard Drive with Recuva:

Recuva found 33720 files on my hard drive f: that it could partially or fully recover. This is a large amount of files and while not all of the files found can be recovered fully, it highlights a big privacy issue.

eraser

Running Eraser:

After right-clicking the central pane I was able to create a new task. The first option was unused space on drive which is the default option in the menu. I selected the f: hard drive from the list. Eraser was displaying my newly selected task in the central pane and I had to right-click that task once again and select Run from the context menu. It took two and a half hours to overwrite all the data on my 100 gigabyte hard drive.

Testing the result with Recuva:

Recuva found one file on drive f: Everything else was not found anymore which leads to the conclusion that this is an excellent way to erase file information that exist on the unused space on your hard drive. This is probably not enough to erase it for the big boys if you know what I mean but every amateur should not be able to restore any of the files that you have deleted this way.

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Responses to How to erase file information on unused disk space

  1. Roys May 3, 2007 at 12:02 pm #

    I use Disk Redactor. Not sure it's that secure but it's really fast - I guess only simple overwriting.

    Maybe I should test the results with Recuva one of these days :)

  2. Steve J May 4, 2007 at 2:41 am #

    Decided to do my own test using Recuva and Disk Redactor:
    50gb Partition with 13gb free
    Recuva reported 22950 files
    ran Disk Redactor (single erase)(took about 7 minutes)
    Recuva reported 22948 files
    ran Disk Redactor (double erase)(took about 15 minutes)
    Recuva reported 22946 files
    So it would seem although it's faster than Eraser it's not as effective

  3. Steve J May 4, 2007 at 3:07 am #

    as an after thought I decided to run Eraser on the same disk since I thought it would give a better idea of the speed comparison (took about 20 minutes)
    Recuva reported 3 files

  4. Roys May 4, 2007 at 3:22 am #

    Hi Steve, thanks for testing for me :) My guess is that Disk Redactor doesn't clear the file entry in the Master File Table (I'm using XP with NTFS) that's why it's so fast. I think I should switch to Eraser now :)

  5. Steve J May 4, 2007 at 3:30 am #

    yep I should have said I'm also using XP on NTFS

  6. Steve J May 4, 2007 at 3:36 am #

    I should also probably have said that when I ran Disk Redactor (and while I was running it I was also doing other things on the machine) I didn't set it to run in the background since as far as I could see Eraser doesn't have that option and I wanted a truer comparison,I did notice that while running Disk Redactor my machine became sluggish, this didn't happen at all when I ran Eraser.

  7. fredden May 8, 2007 at 5:17 pm #

    If you're looking at erasing a hard disk completely, try DBAN (http://dban.sourceforge.net/). Its default settings (or "autonuke" at the prompt) are fine and make it very difficult to recover _any_ information from the drive. This will also erase existing files as well as removed (deleted) ones.

  8. Robert September 13, 2007 at 4:46 am #

    I ran eraser and it only makes it to about 6% and then it has to shut down

  9. Martin September 13, 2007 at 8:11 am #

    That's a strange behavior for Eraser. I would suggest you contact the developers of Eraser and report the problem to them, they surely can help in that matter.

  10. Do not Tempt Fate February 14, 2008 at 2:10 am #

    What an excellent program!I have been looking for this for years. I ran File Recovery (PC Inspector) and found Tons of Porn on unused space on my hard drive. This used laptop I bought looks brand new so I was shocking. Movie clips deleted over a year ago are still recoverable.

    Thank you

  11. Adam M. April 4, 2008 at 12:11 pm #

    Quick question, I was using this "eraser" program as well but i noticed when i set the task on my C: drive it was showing the names of all my files, so here are my two questions

    a.) If i set the eraser to delete the unused data on my C drive will it ruin my windows? or will it just delete the "Hidden" old deleted files that weren't completely deleted.

    b.) As in my first question what would i set the task to if i wanted to sell my hardrive but erase all the hidden files.

    ~A.M

  12. Martin April 4, 2008 at 12:17 pm #

    Adam if you set Eraser to delete the unused disk space on drive c it will only delete old file information on that drive. All current files will remain untouched which means your Windows installation will remain as is.

    If you would sell you hard drive I would format the hard drive and make Eraser delete the unused data - in this case everything - on that drive.

  13. Adam M. April 5, 2008 at 5:26 pm #

    Ok, now i have a bit of a problem. After i used the eraser program to clean out my Drive C of unused data. I opened my mozilla firefox and fonts all look messed up. quite small actually, anything to fix this?

  14. Martin April 5, 2008 at 5:39 pm #

    Adam are you sure it is related to Eraser ? It does not interfere with existing files at all usually.

  15. Adam M. April 5, 2008 at 9:40 pm #

    Yeah, i dont know what it did but it must have erased some important files cause not only did it mess up the fonts & outlook of my internet browser i also had problems with some of my video games. All is good, I reloaded windows so it's fine now.

  16. fsr September 19, 2008 at 6:15 pm #

    Martin, you say it "took two and a half hours to overwrite all the data on my 100 gigabyte" HDD. How many passes are you doing ? I read somewhere only 1 pass will do, file will be irrecoverable.

  17. fsr September 19, 2008 at 6:21 pm #

    Testing with Recuva I have 61.000 files in my Vista machine !

  18. fsr September 20, 2008 at 1:26 pm #

    I don't get it. After the Eraser pass, the only way Recuva shows less files than before is unchecking "show 0 byte files". Right now I have 65.000 unrecoverable files with 0 KB, even more than before !

  19. Jack December 23, 2008 at 1:47 pm #

    Hello,

    Can anyone help please? I've been using Eraser to manually delete files (I'm not technically minded in any way). Now, for the first time, I've just scheduled it to over-write the unusued space on my hard drive (I've been looking to replace Evidence Eliminator which hasn't worked properly for some time). Eraser took ten hours on my 160Gb (at DoD setting) then just stopped. The log reads:

    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSPoliciesx86_policy.8.0.Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_x-ww_caeee1508.0.50727.762.policy (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSPoliciesx86_policy.8.0.Microsoft.VC80.MFC_1fc8b3b9a1e18e3b_x-ww_0f75c32e8.0.50727.762.cat (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSPoliciesx86_policy.8.0.Microsoft.VC80.MFC_1fc8b3b9a1e18e3b_x-ww_0f75c32e8.0.50727.762.policy (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSPoliciesx86_policy.8.0.Microsoft.VC80.OpenMP_1fc8b3b9a1e18e3b_x-ww_7d81c9f98.0.50727.762.cat (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSPoliciesx86_policy.8.0.Microsoft.VC80.OpenMP_1fc8b3b9a1e18e3b_x-ww_7d81c9f98.0.50727.762.policy (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Tools.VisualCPlusPlus.Runtime-Libraries_6595b64144ccf1df_6.0.0.0_x-ww_ff9986d7atl.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Tools.VisualCPlusPlus.Runtime-Libraries_6595b64144ccf1df_6.0.0.0_x-ww_ff9986d7mfc42.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Tools.VisualCPlusPlus.Runtime-Libraries_6595b64144ccf1df_6.0.0.0_x-ww_ff9986d7mfc42u.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Tools.VisualCPlusPlus.Runtime-Libraries_6595b64144ccf1df_6.0.0.0_x-ww_ff9986d7msvcp60.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Tools.VisualCPlusPlus.Runtime-Libraries_6595b64144ccf1df_6.0.9792.0_x-ww_08a6620aatl.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Tools.VisualCPlusPlus.Runtime-Libraries_6595b64144ccf1df_6.0.9792.0_x-ww_08a6620amfc42.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Tools.VisualCPlusPlus.Runtime-Libraries_6595b64144ccf1df_6.0.9792.0_x-ww_08a6620amfc42u.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Tools.VisualCPlusPlus.Runtime-Libraries_6595b64144ccf1df_6.0.9792.0_x-ww_08a6620amsvcp60.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.ATL_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_cbb27474ATL80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.42_x-ww_0de06acdmsvcm80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.42_x-ww_0de06acdmsvcp80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.42_x-ww_0de06acdmsvcr80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_6b128700msvcm80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_6b128700msvcp80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_6b128700msvcr80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80CHS.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80CHT.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80DEU.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80ENU.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80ESP.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80FRA.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80ITA.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80JPN.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFCLOC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_91481303mfc80KOR.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_3bf8fa05mfc80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_3bf8fa05mfc80u.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_3bf8fa05mfcm80.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.MFC_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_3bf8fa05mfcm80u.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC80.OpenMP_1fc8b3b9a1e18e3b_8.0.50727.762_x-ww_6c18549avcomp.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC90.CRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww_d08d0375msvcm90.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC90.CRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww_d08d0375msvcp90.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.VC90.CRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww_d08d0375msvcr90.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.0.0_x-ww_1382d70acomctl32.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.2180_x-ww_a84f1ff9comctl32.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.5512_x-ww_35d4ce83comctl32.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.CPlusPlusRuntime_6595b64144ccf1df_7.0.0.0_x-ww_2726e76amsvcirt.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.CPlusPlusRuntime_6595b64144ccf1df_7.0.0.0_x-ww_2726e76amsvcrt.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.CPlusPlusRuntime_6595b64144ccf1df_7.0.2600.2180_x-ww_b2505ed9msvcirt.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.CPlusPlusRuntime_6595b64144ccf1df_7.0.2600.2180_x-ww_b2505ed9msvcrt.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.CPlusPlusRuntime_6595b64144ccf1df_7.0.2600.5512_x-ww_3fd60d63msvcirt.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.CPlusPlusRuntime_6595b64144ccf1df_7.0.2600.5512_x-ww_3fd60d63msvcrt.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.GdiPlus_6595b64144ccf1df_1.0.0.0_x-ww_8d353f13GdiPlus.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.GdiPlus_6595b64144ccf1df_1.0.2600.2180_x-ww_522f9f82GdiPlus.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.GdiPlus_6595b64144ccf1df_1.0.2600.3352_x-ww_81af8e88GdiPlus.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.GdiPlus_6595b64144ccf1df_1.0.2600.5512_x-ww_dfb54e0cGdiPlus.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.Networking.Dxmrtp_6595b64144ccf1df_5.2.2.3_x-ww_468466a7dxmrtp.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.Networking.RtcDll_6595b64144ccf1df_5.2.2.3_x-ww_d6bd8b95rtcdll.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_Microsoft.Windows.Networking.RtcRes_6595b64144ccf1df_5.2.2.3_en_16a24bc0rtcres.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_System.EnterpriseServices_b03f5f7f11d50a3a_2.0.0.0_x-ww_7d5f3790System.EnterpriseServices.dll (Protected File).
    23/12/2008 11:22:17 AM: Failed to erase unused space on C:WINDOWSWinSxSx86_System.EnterpriseServices_b03f5f7f11d50a3a_2.0.0.0_x-ww_7d5f3790System.EnterpriseServices.Wrapper.dll (Protected File).
    23/12/2008 11:33:42 AM: Removed a task (C:).

    Thanks for any advice.

  20. Gary April 1, 2013 at 2:22 am #

    Hi Guys,

    I carry client sensitive data on my laptop and as we speak Eraser is erasing my unused space.

    Sounds perfect. My simple question is, Eraser has a dozen plus types of erase options and passes, Gutmann 35passes, Gutman 7 passses, DoD, etc

    Which is 'the best'? I have all the time in the world so might use several of these but I am trying to work out which is the gold-standard. Or will any do.

    • Martin Brinkmann April 1, 2013 at 3:31 am #

      Gary any will do really do protect the data from software recovery. I suggest you run a file recovery software like Recuva after you have deleted the free space to see if that is really the case.

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