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)