1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
.\" This definition swiped from the gcc(1) man page
.de Sp
.if n .sp
.if t .sp 0.4
..
.TH SFILL 1
.SH NAME
sfill \- secure free disk and inode space wiper (secure_deletion toolkit)
.SH SYNOPSIS
.B sfill [-f] [-i] [-I] [-l] [-l] [-v] [-z] directory/mountpoint
.SH DESCRIPTION
.I 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.
.PP
The
.I secure data deletion
process of sfill goes like this:
.PP
.TP
.B *
1 pass with 0xff
.TP
.B *
5 random passes. /dev/urandom is used for a secure RNG if available.
.TP
.B *
27 passes with special values defined by Peter Gutmann.
.TP
.B *
5 random passes. /dev/urandom is used for a secure RNG if available.
.PP
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.
.PP
.SH COMMANDLINE OPTIONS
.PP
.TP
.B \-f
fast (and insecure mode): no /dev/urandom, no synchronize mode.
.TP
.B \-i
wipe only free inode space, not free disk space
.TP
.B \-I
wipe only free disk space, not free inode space
.TP
.B \-l
lessens the security. Only two passes are written: one mode with 0xff
and a final mode with random values.
.TP
.B \-l
-l for a second time lessons the security even more: only one random pass
is written.
.TP
.B \-v
verbose mode
.TP
.B \-z
wipes the last write with zeros instead of random data
.PP
.PP
.B directory/mountpoint
this is the location of the file created in your filesystem. It should
lie on the partition you want to write.
.PP
.SH LIMITATIONS
.TP
.B 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 ...
.TP
.B NFS
Beware of NFS. You can't ensure you really completely wiped your data
from the remote disks. (especially because of caching)
.TP
.B Raid
Raid Systems use stripped disks and have got large caches. It's hard to wipe
them.
.TP
.B swap
Some of your data might have a copy in your swapspace.
.I sswap
is available for this task.
.PP
.SH 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 :)
.SH AUTHOR
.Sp
van Hauser / THC
.I <vh@thc.org>
.SH DISTRIBUTION
The newest version of the
.I secure_deletion package
can be obtained from
.I http://www.thc.org
.Sp
.I sfill
and the
.I secure_deletion package
is (C) 1997-2003 by van Hauser / THC (vh@thc.org)
.Sp
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.
.Sp
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.
.SH SEE ALSO
.I srm
(1),
.I sswap
(1),
.I smem
(1)
|
