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fwsnort (Firewall Snort)
Version: 1.6.2
Author: Michael Rash <>
Snort is a registered trademark of Sourcefire, Inc
(See the INSTALL file in the source directory.)
If are installing fwsnort from sources (i.e. not through a distribution
package manager such as RPM or apt), you can just run the "" script.
It takes care of upgrades, and it will merge any customized configuration
variables in the /etc/fwsnort/fwsnort.conf file with the new file in the
source directory. Even if you are using a distribution package manager, you
can still run the script in order to preserve any existing
configuration. However, in this case the script will also put in
place fwsnort according to how it normally handles installation paths, and
these may not match how your distribution package manager normally handles
fwsnort is a perl script that translates Snort rules into equivalent iptables
rules. Some Snort rule options (such as "pcre") have no direct translation
into iptables options so not all Snort rules can be translated. However
approximately 65% of all Snort-2.3.3 (the last release of Snort under the GPL)
signatures can be successfully translated through the use of the iptables
string match module. When tranlating Snort rules, fwsnort makes heavy use of
the iptables string match extension with its "--hex-string" option (added to
iptables by the fwsnort project) which accepts Snort "content" argument with
hex bytes between "|" chars (such as "|5a 4e|"). This allows the content
fields in Snort rules to be directly input into iptables rulesets from the
command line. fwsnort alse parses the running iptables policy on the machine
in order to determine which Snort rules are applicable to the specific policy
loaded on the machine.
fwsnort requires the iptables string match module in order to be able to
detect application layer attacks. If you are running modern Linux
distribution then it is likely that the kernel has been compiled with iptables
string matching support, and fwsnort will test this.
fwsnort is compatible with iptables only, hence fwsnort will exclusively run
on Linux running a 2.6 series kernel (with some support for 2.4 kernels as
Copyright (C) 2003-2010 Michael Rash (
fwsnort is distributed under the GNU General Public License (GPLv2), and the
latest version may be downloaded from
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; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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