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 thieves, law enforcement or other threats.  The  wipe
       algorithm  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 finished.

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.

       fat32  The  size  of  files  with  fat32 filesystems is limited to 4 GB; sfill can fail to
              smash the complete filesystem if the free space is bigger than this limit,  because
              this  command  creates  the biggest possible anonymous file and securely erases its
              content.

              To work around this limitation, the recommended package  libgsecuredelete0  can  be
              installed,  and  one  can call the script /usr/libexec/libgsecuredelete0/gsd-sfill-
              helper which creates as many anonymous files as the filesystem can bare,  and  then
              smashes them all.

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), sdmem (1)

                                                                                         SFILL(1)