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Thread: secure delete data purge ubuntu

  1. #1
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    secure delete data purge ubuntu

    Does anyone know how to securely delete data from harddrive of ubuntu as OS. completely wipe which even the forensics can't even retrive. i have given up windows cos some people told me that linux is much more secure in sensitive datas. thanks people ...

  2. #2
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    May 2007
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    Arizona
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    Xubuntu 11.10 Oneiric Ocelot

    Re: secure delete data purge ubuntu



  3. #3
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    Mar 2008
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    Re: secure delete data purge ubuntu

    Why what are worried someones going to find. I gotta say you asked that kinda strangely. If you tell me its because your affraid of getting busted for something I Dont care about I will tell you.

  4. #4
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    Oct 2007
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    Re: secure delete data purge ubuntu

    nicedude, well ya ... issn't that obvious. i have got sensitive data which i don't want others to know about .. u don't have to tell me if u don't want to .. i love linux because of the spirits of sharing not to question others oh y u want this and that for ..

  5. #5
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    Oct 2007
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    Re: secure delete data purge ubuntu

    thanks man ..

  6. #6
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    May 2006
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    Switzerland
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    Ubuntu 12.04 Precise Pangolin

    Re: secure delete data purge ubuntu

    Quote Originally Posted by wenhui100 View Post
    completely wipe which even the forensics can't even retrive.
    That's difficult to achieve.

    What I would suggest is that you make yourself familiar with harddrive encryption, or at least folder encryption. Please see the links below. The point here is that whatever is stored or deleted from those encrypted disks or folders is still encrypted and thus it's still impossible to decypher.

    (I myself use this method: "encfs" ... It's "good enough" for what I need it.)

    "HOWTO: Encrypted directory with EncFS"
    http://ubuntuforums.org/showthread.php?t=148600

    "Using TrueCrypt on Ubuntu for Encryption"
    http://tombuntu.com/index.php/2007/0...or-encryption/

    "TrueCrypt With GUI On Ubuntu 7.10"
    http://www.howtoforge.com/truecrypt-...on-ubuntu-7.10


    Full disk encryption:

    "Step-by-step: Encrypted Ubuntu 7.10"
    http://news.softpedia.com/news/Encry...10-68383.shtml


    Then, there are other things you'd need to be aware of: There are important differences between the various filesystem types available on Linux. Some such as ReiserFS make it very easy to retrieve data again. So if you value your privacy: Don't use ReiserFS! Others such as Ext3 make it far more difficult to retrieve deleted data again but I guess people working in computer forensics would still know how and might still have success by scanning the entire disk on a low-level and then retrieving chunk by chunk of whatever you deleted.

    As far as making undelete operations very difficult is concerned, I'd say XFS takes the crown: Whenever you delete something from an XFS filesystem, XFS will automagically reassign the freed blocks to something else (whatever task might be in need of free blocks) and whatever just got deleted has a high chance of getting overwritten in the next second. Add to this that the XFS filesystem does know a "defrag" utility ("xfs_fsr" program from the "xfsdump" package) which technically isn't necessary (XFS will already do whatever it can to avoid fragmentation just like the other Linux filesystems too) but when executed will cause files to be rearranged on the disk, thus making it very likely that whatever just got deleted and whatever free space that generated will be overwritten in the next second with whatever is being re-arranged on the XFS disk. So it would be good to always keep a few double-layer DVD ISO images (8.5 GB size) around and then just copy them around on the XFS filesystem after you deleted something from there. Chances are that XFS will overwrite whatever you deleted with whatever large file you are copying around.

    I know ... this is by no means a perfect guarantee, but it sure helps getting rid of old data fragments you don't want to ever to come back again.


    As for actually deleting files: I'd suggest you install this utility from the repos: "wipe". So you'd type this into a terminal:
    Code:
    sudo apt-get install wipe
    And then you should familiarize yourself with how it works and what it can do for you by reading its manual:
    Code:
    man wipe
    Read it carefully.

    So to really achieve what you wanted, you'd have to:
    - use full hardisk encryption
    - use XFS as filesystem
    - use "wipe" for secure file deletion and not any other method
    - everytime after something got deleted make sure you copy and move large files around so any potentially remaining data blocks of the deleted file get overwritten again.

    In my opinion only this combo will help you achieve what you want and make it really hard for anyone to retrieve anything.


    I hope this helped.

  7. #7
    Join Date
    May 2006
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    Ubuntu 12.04 Precise Pangolin

    Re: secure delete data purge ubuntu

    Nice overview ... BUT: There is one factual error on the page.

    Starting with ext3, Linux filesystems overwrite files with zeros when you delete them, rather than just marking the file as "free space."
    Sorry, but that just isn't true. Ext3 will overwrite the pointers in the superblocks (which point to the blocks which contain the actual data) with zeros, yes. That's why all the undelete utilities which used to work for Ext2 will no longer work with Ext3: Ext2 behaved as it says in the text: it just marked the pointers as being "deleted", but it didn't wipe them as Ext3 does. BUT: Ext3 does not wipe the data contents themselves! So while it will be very hard to get the filename back from a deleted file on an Ext3 filesystem, getting the data back from Ext3 is possible if you do a low-level search, byte by byte, chunk by chunk. And that's precisely how they'd do that if your harddisk ever ended up in the hands of the forensics guys.

    So the claim above that a standard delete operation on Ext3 will overwrite the complete file is false. Only the pointers in the superblocks get overwritten, but the data contents are still there and could still be retrieved. Details here:
    http://batleth.sapienti-sat.org/proj.../ext3-faq.html

    And here is a description how retrieving deleted files from Ext3 works:
    http://www.xs4all.nl/~carlo17/howto/undelete_ext3.html

  8. #8
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    Jan 2008
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    Bentonville AR
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    Ubuntu 13.10 Saucy Salamander

    Re: secure delete data purge ubuntu

    Here is a file shredding script that you could add:
    Code:
    #!/bin/bash
    
    if [[ -a /dev/urandom ]]; then
        randomizer=/dev/urandom;
    elif [[ -a /dev/random ]]; then
        randomizer=/dev/random;
    fi
    
    echo $NAUTILUS_SCRIPT_SELECTED_URIS > ~/.gnome2/temp_shred_list
    
    for file in $(cat ~/.gnome2/temp_shred_list); do
    
    shortfile=$(echo $file | sed -e 's/\%20/\ /g' -e 's/.*\///g')
    
    file_name=$(echo $file | sed -e 's/file:\/\///g' -e 's/\%20/\ /g')
    
    zenity --question --title "Shredder" --text "Really shred $shortfile?"
    
    if (( "$?" == 1 )) ; then
        exit
    else
        if [[ $randomizer == "" ]]; then
            shred -u -z -n 50 "$file_name"
            if (( $? == 0 )); then
                zenity --info --text="$shortfile has been shred" --title "Success"
            else    zenity --info --text="$shortfile couldn't be shred" --title "Failure"
            fi
        else    shred -u -z -n 50 --random-source=$randomizer "$file_name"
            if (( $? == 0 )); then
                zenity --info --text="$shortfile has been shred" --title "Success"
            else    zenity --info --text="$shortfile couldn't be shred" --title "Failure"
            fi
        fi
    fi;
    
    done
    
    rm -f ~/.gnome2/temp_shred_list
    Sayak Banerjee
    KDE Sysadmin | KDE e.V.
    Need help? Contact us.

  9. #9
    Join Date
    Mar 2008
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    Ubuntu 8.04 Hardy Heron

    Re: secure delete data purge ubuntu

    or howbout, formating your computer and then dumping more stuff on it from your external harddrive and then again format it. Do it about 7 times or so I think.

    Or if possible, simply burn it

  10. #10
    Join Date
    Jan 2008
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    Bentonville AR
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    Ubuntu 13.10 Saucy Salamander

    Re: secure delete data purge ubuntu

    Quote Originally Posted by MongooseCage View Post
    Or if possible, simply burn it
    Sayak Banerjee
    KDE Sysadmin | KDE e.V.
    Need help? Contact us.

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