sfill

SFILL(1)                    General Commands Manual                   SFILL(1)



NAME
       sfill - secure free disk and inode space wiper (secure_deletion
       toolkit)


SYNOPSIS
       sfill [-f] [-i] [-I] [-l] [-l] [-v] [-z] directory/mountpoint


DESCRIPTION
       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.

       The secure data deletion process of sfill goes like this:

       *      1 pass with 0xff

       *      5 random passes. /dev/urandom is used for a secure RNG if
              available.

       *      27 passes with special values defined by Peter Gutmann.

       *      5 random passes. /dev/urandom is used for a secure RNG if
              available.

       afterwards as many temporary files as possible are generated to wipe
       the free inode space. After no more temporary files can be created,
       they are removed and sfill is finnished.

COMMANDLINE OPTIONS
       -f     fast (and insecure mode): no /dev/urandom, no synchronize mode.

       -i     wipe only free inode space, not free disk space

       -I     wipe only free disk space, not free inode space

       -l     lessens the security. Only two passes are written: one mode with
              0xff and a final mode with random values.

       -l     -l for a second time lessons the security even more: only one
              random pass is written.

       -v     verbose mode

       -z     wipes the last write with zeros instead of random data

       directory/mountpoint this is the location of the file created in your
       filesystem. It should lie on the partition you want to write.

LIMITATIONS
       FILESYSTEM INTELLIGENCE
              Most filesystems (ext2, ffs, etc.) have several features
              included to enhance performance, which will result in that sfill
              might not receive all available free space. Sad but true.
              Nothing can be done about that ...

       NFS    Beware of NFS. You can't ensure you really completely wiped your
              data from the remote disks. (especially because of caching)

       Raid   Raid Systems use stripped disks and have got large caches. It's
              hard to wipe them.

       swap   Some of your data might have a copy in your swapspace.  sswap is
              available for this task.


BUGS
       No bugs. There was never a bug in the secure_deletion package (in
       contrast to my other tools, whew, good luck ;-) Send me any that you
       find.  Patches are nice too :)


AUTHOR
       van Hauser / THC <vh@thc.org>


DISTRIBUTION
       The newest version of the secure_deletion package can be obtained from
       http://www.thc.org

       sfill and the secure_deletion package is (C) 1997-2003 by van Hauser /
       THC (vh@thc.org)

       This program is free software; you can redistribute it and/or modify it
       under the terms of the GNU General Public License as published by the
       Free Software Foundation; Version 2.

       This program is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.


SEE ALSO
       srm (1), sswap (1), smem (1)



                                                                      SFILL(1)