simple way to securely destroy deleted files in a file system
in [Debian]
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From: H.S. on 15 Jul 2010 12:10 I have a couple of hard disks in a computer which is to be recycled. I want the windows OS in it to remain functional, but I want to be sure that I have deleted all my personal files securely (never used the OS that much anyway and there is hardly any important info in its registry or browser). There are a number of documents that were deleted in Windows the usual way (Shift+del) and I just want to make them unrecoverable. Its first and second partitions (sdc1 and sdc2) are vfat. I was thinking of mounting these on /mnt/scd1 (and scd2) and then doing: # dd if=/dev/zero > /mnt/sdc1/zeros.bin; rm -f /mnt/sdc1/zeros.bin and the same for scd2. The idea is fill the partition with new data thus overwriting any deleted files' data that is lying around. Would that be adequate? The objective is just to prevent a casual recovery, reading and copying of the data by a future user, so I don't need multiple over-writes. -- Please reply to this list only. I read this list on its corresponding newsgroup on gmane.org. Replies sent to my email address are just filtered to a folder in my mailbox and get periodically deleted without ever having been read. -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/i1nbkd$k5o$1(a)dough.gmane.org
From: Wolodja Wentland on 15 Jul 2010 12:40 On Thu, Jul 15, 2010 at 12:05 -0400, H.S. wrote: > > I have a couple of hard disks in a computer which is to be recycled. I > want the windows OS in it to remain functional, but I want to be sure > that I have deleted all my personal files securely (never used the OS > that much anyway and there is hardly any important info in its registry > or browser). There are a number of documents that were deleted in > Windows the usual way (Shift+del) and I just want to make them > unrecoverable. > > Its first and second partitions (sdc1 and sdc2) are vfat. I was thinking > of mounting these on /mnt/scd1 (and scd2) and then doing: > # dd if=/dev/zero > /mnt/sdc1/zeros.bin; rm -f /mnt/sdc1/zeros.bin > > and the same for scd2. The idea is fill the partition with new data thus > overwriting any deleted files' data that is lying around. Would that be > adequate? The objective is just to prevent a casual recovery, reading > and copying of the data by a future user, so I don't need multiple > over-writes. Take a look at "secure-delete" which contains "sfill" which can be used to fill the available free space on a hd with random (and specifically crafted) data to ensure that data recovery is impossible. I am not sure if it works with vfat though :-\ good luck Wolodja -- .''`. Wolodja Wentland <wentland(a)cl.uni-heidelberg.de> : :' : `. `'` 4096R/CAF14EFC `- 081C B7CD FF04 2BA9 94EA 36B2 8B7F 7D30 CAF1 4EFC
From: Perry E. Metzger on 15 Jul 2010 13:40 On Thu, 15 Jul 2010 12:05:33 -0400 "H.S." <hs.samix(a)gmail.com> wrote: > > I have a couple of hard disks in a computer which is to be > recycled. I want the windows OS in it to remain functional, but I > want to be sure that I have deleted all my personal files securely > (never used the OS that much anyway and there is hardly any > important info in its registry or browser). There are a number of > documents that were deleted in Windows the usual way (Shift+del) > and I just want to make them unrecoverable. > > Its first and second partitions (sdc1 and sdc2) are vfat. I was > thinking of mounting these on /mnt/scd1 (and scd2) and then doing: > # dd if=/dev/zero > /mnt/sdc1/zeros.bin; rm -f /mnt/sdc1/zeros.bin > > and the same for scd2. The idea is fill the partition with new data > thus overwriting any deleted files' data that is lying around. > Would that be adequate? The objective is just to prevent a casual > recovery, reading and copying of the data by a future user, so I > don't need multiple over-writes. I suggest dd'ing /dev/zero over the raw disk partition instead. That will zero out every single block of the file system. You can probably just do dd if=/dev/zero of=/dev/scd bs=1M or some moral equivalent. -- Perry E. Metzger perry(a)piermont.com -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/20100715133812.64fb6db0(a)jabberwock.cb.piermont.com
From: H.S. on 15 Jul 2010 14:00 On 15/07/10 01:38 PM, Perry E. Metzger wrote: > On Thu, 15 Jul 2010 12:05:33 -0400 "H.S." <hs.samix(a)gmail.com> wrote: >> Its first and second partitions (sdc1 and sdc2) are vfat. I was >> thinking of mounting these on /mnt/scd1 (and scd2) and then doing: >> # dd if=/dev/zero > /mnt/sdc1/zeros.bin; rm -f /mnt/sdc1/zeros.bin >> >> and the same for scd2. The idea is fill the partition with new data >> thus overwriting any deleted files' data that is lying around. >> Would that be adequate? The objective is just to prevent a casual >> recovery, reading and copying of the data by a future user, so I >> don't need multiple over-writes. > > I suggest dd'ing /dev/zero over the raw disk partition instead. That > will zero out every single block of the file system. You can probably > just do > > dd if=/dev/zero of=/dev/scd bs=1M Yes, but that would wipe out everything, the OS as well. I was looking for just making the already deleted files unrecoverable by a casual user. In other words, since a deleted file frees the space on disk, by filling up the disk with all zeros and then deleting that zeros file would be overwriting the earlier deleted files with zero. Am I correct in this? -- Please reply to this list only. I read this list on its corresponding newsgroup on gmane.org. Replies sent to my email address are just filtered to a folder in my mailbox and get periodically deleted without ever having been read. -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/i1ni29$cpk$1(a)dough.gmane.org
From: H.S. on 15 Jul 2010 14:10 On 15/07/10 12:31 PM, Wolodja Wentland wrote: >> >> Its first and second partitions (sdc1 and sdc2) are vfat. I was thinking >> of mounting these on /mnt/scd1 (and scd2) and then doing: >> # dd if=/dev/zero > /mnt/sdc1/zeros.bin; rm -f /mnt/sdc1/zeros.bin >> >> and the same for scd2. The idea is fill the partition with new data thus >> overwriting any deleted files' data that is lying around. Would that be >> adequate? The objective is just to prevent a casual recovery, reading >> and copying of the data by a future user, so I don't need multiple >> over-writes. > > Take a look at "secure-delete" which contains "sfill" which can be used > to fill the available free space on a hd with random (and specifically > crafted) data to ensure that data recovery is impossible. I am not sure > if it works with vfat though :-\ I am looking at its man page, which starts with "sfill is designed to delete data which lies on available diskspace on mediums in a secure manner which can not be recovered by thiefs, law enforcement or other threats. The wipe algorythm is based on the paper "Secure Deletion of Data from Magnetic and Solid-State Memory" presented at the 6th Usenix Security Symposium by Peter Gutmann, one of the leading civilian cryptographers." Talk about overkill! Sfill has some options which will make it easier and faster (by not doing it in the most robust and time expensive fashion) to delete/free disk space. I just have to verify how it work and I don't inadvertently delete files which I am not supposed to. Thanks. > good luck > > Wolodja -- Please reply to this list only. I read this list on its corresponding newsgroup on gmane.org. Replies sent to my email address are just filtered to a folder in my mailbox and get periodically deleted without ever having been read. -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/i1nibe$dv9$1(a)dough.gmane.org
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