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  • Complete erasure of confidential files

    We have been running some considerable discussion in the Liberty Basic conforum on the possibility of creating a program to successfully overwrite any confidential files, before deletion. This would be done in the hope if anyone manages to resurrect such files after being deleted, the original confidential data will have been overwritten such as by random CHR$. The overwriting could be done several times, and the whole process be needed such as when disposing of an old PC.

    Some doubt was expressed as to whether the new overwritten file would occupy the same area on the hard drive, even if it contains the exact same number of bytes. But the system of overwriting using Random Access and Binary was considerable by some as possible.

    What do you think? Gordon

  • #2
    Re: Complete erasure of confidential files

    My currrent understanding is that the file would have to be overwritten at least 7 times, possibly more now. I know the police/services data recovery teams can get back data that has been "securely" erased that many times. The basics being that the 1 or 0 isn't actually off or on but grades in-between, if you can determine what files were written when then you can remove the addition/subtraction to the grade and get a different point in time to work from.

    There are also temp files/system recovery etc that would need removing too so generally all of the free space etc would have to be done. Destroying the disk is probably the best way to go (and is fun too, although my neighbours didn't like it!)
    cheers
    Andy

    Please read this before you post:


    Quis custodiet ipsos custodes?

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    • #3
      Re: Complete erasure of confidential files

      You might look at fileshredder software packages.
      However using a power drill is the safest way
      Marcel
      Technical Consultant
      Netherlands
      http://www.phetios.com
      http://blog.nessus.nl

      MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
      "No matter how secure, there is always the human factor."

      "Enjoy life today, tomorrow may never come."
      "If you're going through hell, keep going. ~Winston Churchill"

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      • #4
        Re: Complete erasure of confidential files

        It was my understanding that if you have enough time and enough money anything that has ever been on a hard drive is recoverable, and consequently the only way to ensure the data is not recoverable is to destroy or damage the platters.

        It's also very therapeutic by all accounts.
        BSc, MCSA: Server 2008, MCSE, MCSA: Messaging, MCTS
        sigpic
        Cruachan's Blog

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        • #5
          Re: Complete erasure of confidential files

          Complete physical eradication is the only sure fire way.

          Now there's a limit as to what you can recover with just software. To what limit do you want to ensure the data is erased?
          ** Remember to give credit where credit is due and leave reputation points where appropriate **

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          • #6
            Re: Complete erasure of confidential files

            Although completely physically destroying a drive maybe the only safe way to destroy confidential information, it means the PC cannot be handed / sold to anther person, without a new hard drive being bought. This specially if the proposed new owner has no need to use the Internet, and does not need a fancy modern PC.

            So ideally only a few confidential files need deleing or made unreadable, which such as the Freeware at http://www.tolvanen.com/eraser/ claims to do. Yet Second hand PCs are sold everywhere.

            Gordon

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            • #7
              Re: Complete erasure of confidential files

              without nothing i'd full format the space and copy giant files onto it till it's full and does this for several times...

              beyond this as mentioned either a shredder or a hammer

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              • #8
                Re: Complete erasure of confidential files

                I think Mark Russinovich's SDelete should be enough.

                Sorin Solomon


                In order to succeed, your desire for success should be greater than your fear of failure.
                -

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                • #9
                  Re: Complete erasure of confidential files

                  Adding to the other suggestions have a read on this Blog and the comments: http://geeksaresexy.blogspot.com/200...o-get-rid.html

                  The choice is yours..... (Drill/smelter or softerase .. or both )
                  Caesar's cipher - 3

                  ZKHQ BRX HYHQWXDOOB GHFLSKHU WKLV BRX ZLOO UHDOLVH LW ZDV D ZDVWH RI WLPH!

                  SFX JNRS FC U6 MNGR

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                  • #10
                    Re: Complete erasure of confidential files

                    Thanks guys for all your help.

                    I will also concoct my own program making use of SDELETE if anyone wants a copy

                    Gordon

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                    • #11
                      Re: Complete erasure of confidential files

                      Originally posted by GordonSweet View Post
                      I will also concoct my own program making use of SDELETE if anyone wants a copy

                      Gordon
                      Make sure you read the Sysinternals Licensing terms before you do so though, to ensure you could do that.
                      Not sure if it falls under this:
                      Q: May I distribute Sysinternals utilities in my software, on my website, or with my magazine?
                      A: No. We are not offering any distribution licenses, even if the 3rd party is distributing them for free. We encourage people to download the utilities from our download center where they can be assured to get the most recent version of the utility.
                      Caesar's cipher - 3

                      ZKHQ BRX HYHQWXDOOB GHFLSKHU WKLV BRX ZLOO UHDOLVH LW ZDV D ZDVWH RI WLPH!

                      SFX JNRS FC U6 MNGR

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                      • #12
                        Re: Complete erasure of confidential files

                        Don't forget it's not Sysinternals anymore, but Microsoft ...

                        Sorin Solomon


                        In order to succeed, your desire for success should be greater than your fear of failure.
                        -

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                        • #13
                          Re: Complete erasure of confidential files

                          I quite agree I have to be careful. But if you look at the umpteen free programs and code on my site at http://www.sigord.co.uk/ I NEVER charge for any, and only in a few instances include third party files such as DLLs. This effort of mine I have finished using BBC BASIC for Windows to activate a filedialog to run any SDELETE on any file a number of chosen passes, will only be available to anyone who asks for it.

                          However I must admit I find the laws on Program code baffling. My site has many programs by others downloaded in bulk from a site hosting 25 year old code for the original UK BBC Computer, kept on behalf of a magazine once called Beebug. I believe the copyright on code is supposed to last some 50 years. But if you adapt the code to run on modern Windows, is the original copyright really still completely valid.?

                          Anyone no one has complained, and no one I emailed seems interested in Beebug files.

                          Gordon

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                          • #14
                            Re: Discount baby phat

                            I personally use DBAN for all HDD wiping.

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