fwlogwatch - a firewall log analyzer, report generator and realtime
fwlogwatch [options] [input_files]
fwlogwatch produces Linux ipchains, Linux netfilter/iptables,
Solaris/BSD/Irix/HP-UX ipfilter, ipfw, Cisco IOS, Cisco PIX, NetScreen,
Windows XP firewall, Elsa Lancom router and Snort IDS log summary
reports in plain text and HTML form and has a lot of options to analyze
and display relevant patterns. It can produce customizable incident
reports and send them to abuse contacts at offending sites or CERTs.
Finally, it can also run as daemon (with web interface) doing realtime
log monitoring and reporting anomalies or starting attack
These options are independent from the main modes of operation.
-h Show the available options.
-L Show time of the first and the last log entry. The input file(s)
can be compressed or plain log file(s). Summary mode will show
the time of the first and last packet log entry, this log times
mode will show the time of the first and last entry overall.
-V Show version and copyright information and the options used to
The global options for all modes are:
-b Show the amount of data in bytes this entry represents, this is
the sum of total packet lengths of packets matching this rule
(obviously only available for log formats that contain this
Use the alternate configuration file config instead of the
default configuration file /etc/fwlogwatch/fwlogwatch.config
(which does not need to exist). Only options not specified in
the files can be overridden by command line options.
-D Do not differentiate destination IP addresses. Useful for
finding scans in whole subnets.
-d Differentiate destination ports.
Specific hosts, ports, chains and branches (targets) can be
selected or excluded, selections an exclusions can be added and
combined. The format is composed of one of the functions i
include or e exclude, then one of the parameters h host, p port,
c chain or b branch. In case of a host or port a third parameter
for s source or d destination is needed. Finally, the object is
directly appended, in case of a host this is an IP address
(networks can be specified in CIDR format), port is a number and
chain and branch are strings. To show entries with destination
port 25 you would use -Eipd25 and to exclude entries which have
the class C network 192.168.1.0 as source or belong to the chain
INPUT: -Eehs192.168.1.0/24 -EecINPUT
If you only want to see a fixed maximum amount of entries (e.g.
the "top 20") this option will trim the output for you.
When analyzing large amounts of data you usually aren’t
interested in entries that have a small count. You can hide
entries below a certain threshold with this option.
-N Enable service lookups. Port numbers will be looked up in
-n Enable DNS lookups. Host names will be resolved (reverse and
forward lookup with a warning if they don’t match). This makes
summary generation very slow if a lot of different hosts appear
in the log file. Resolved host names are cached.
This is the sort order of the summary and packet cache. Since
entries often are equal in certain fields you can sort by
several fields one after another (the sort algorithm is stable,
so equal entries will remain sorted in the order they were
sorted before). The sort string can be composed of up to 11
fields of the form ab where a is the sort criteria: c count, t
start time, e end time, z duration, n target name, p protocol, b
byte count (sum of total packet lengths), S source host, s
source port, D destination host and d destination port. b is
the direction: a ascending and d descending. Sorting is done in
the order specified, so the last option is the primary criteria.
The default in summary mode is tacd (start with the highest
count, if two counts match list the one earlier in time first)
of which ta is built in, so if you specify an empty sort string
or everything else is equal entries will be sorted ascending by
time. The realtime response mode default is cd ( ta is not built
Only use certain parsers, where the log format can be one or a
combination of: i ipchains, n netfilter, f ipfilter, b ipfw, c
Cisco IOS, p Cisco PIX, e NetScreen, w Windows XP, l Elsa Lancom
and s Snort. The default is to use all parsers except the ones
for NetScreen, Windows XP, Elsa Lancom and Snort logs.
-p Differentiate protocols. This is activated automatically if you
differentiate source and/or destination ports.
-s Differentiate source ports.
Set title as title of the report and status page and as subject
for reports sent by email.
-v Be verbose. You can specify it twice for more information. In
very verbose mode while parsing the log file you will see "."
for relevant packet filter log entries, "r" for ’last message
repeated’ entries concerning packet filter logs, "o" for packet
filter log entries that are too old and "_" for entries that are
not packet filter logs.
-y Differentiate TCP options. All packets with a SYN are listed
separately, other TCP flags are shown in full format if they are
available (ipchains does not log them, netfilter and ipfilter
do, Cisco IOS doesn’t even log SYNs).
LOG SUMMARY MODE
This are additional options that are only available in log summary
-e Show timestamp of last packet logged. End times are only
available if there is more than one packet log entry with unique
Process recent events only. See TIME FORMAT below for the time
Specify an output file.
-S Do not differentiate source IP addresses.
The summary will be sent by email to this address. If HTML
output is selected the report will be embedded as attachment so
HTML-aware mail clients can show it directly.
-t Show timestamp of first packet logged.
-W Look up information about the source addresses in the whois
database. This is slow, please don’t stress the registry with
too many queries.
-w Produce output in HTML format.
-z Show time interval between start and end time of packet log
entries. This is only available if there is more than one packet
log entry with unique characteristics.
INTERACTIVE REPORT MODE
The interactive report mode is a summary mode extension with the
following additional options:
Enter interactive report mode. count is the minimum number of
log entries you want to start reporting at. A summary of the
corresponding entries will be shown and a report generated for
each one. The more of the options above you use the more fields
of the report will be filled in.
This is the address the email containing the report will be sent
This is the email address of the abuse contact or CERT the
report will be sent to.
These email recipients will get a carbon copy of the report
(e.g. for your archives).
Template file for report (defaults to
REALTIME RESPONSE MODE
-R Enter realtime response mode. This means: detach and run as
daemon until the TERM signal (kill) is received. The HUP signal
forces a reload of the configuration file, the USR1 signal
forces fwlogwatch to reopen and read the input file from the
beginning (useful e.g. for log rotation). All output can be
followed in the system log.
Alert threshold. Notify or start countermeasures if this limit
is reached. Defaults to 5.
Forget events that happened this long ago (defaults to 1 day).
See TIME FORMAT below for the time options.
This option defines a host or network in CIDR notation that will
never be blocked or other actions taken against. To specify more
than one, use the -k parameter again for each IP address or
network you want to add.
-A The notification script is invoked when the threshold is
reached. A few examples of possible notifications are included
in fwlw_notify, you can add your own ones as you see fit.
-B The response script is invoked when the threshold is reached.
Using the example script fwlw_respond this will block the
attacking host with a new firewall rule. A new chain for
fwlogwatch actions is inserted in the input chain and block
rules added as needed. The chain and its content is removed if
fwlogwatch is terminated normally. The example scripts contain
actions for ipchains and netfilter, you can modify them or add
others as you like.
Activate the internal web server to monitor and control the
current status of the daemon. It listens on the specified port
and by default only allows connections from localhost. The
default user name is admin and the default password is fwlogwat
(since DES can only encrypt 8 characters). All options related
to the status web server can be changed in the configuration
You can specify one or more input files (if none is given it defaults
to /var/log/messages ). Relevant entries are automatically detected so
combined log files (e.g. from a log host) are no problem. Compressed
files are supported (except in realtime response mode where they don’t
make sense anyway). The ’-’ sign may be used for reading from standard
input (stdin). In realtime response mode the file needs to be specified
with an absolute path since the daemon uses the file system root (/) as
Time is specified as nx where n is a natural number and x is one of the
following: s for seconds (this is the default), m for minutes, h for
hours, d for days, w for weeks, M for months and y for years.
Default configuration file.
Default template for incident reports.
Default input log file.
Default PID file generated by the daemon in realtime response
mode if configured to do so.
FEATURES ONLY IN CONFIGURATION FILE
The following features are only available in the configuration file and
not on the command line, they are presented and explained in more
detail in the sample configuration file.
HTML colors and stylesheet
The colors of the HTML output and status page can be customized,
an external cascading stylesheet can be referenced.
Realtime response options
Verification of ipchains rules, PID file handling, the user
fwlogwatch should run as, the location of the notification and
response scripts, which address the status web server listens
on, which host can connect, the refresh interval of the status
page and the admin name and password can be configured.
Since fwlogwatch is a security tool special care was taken to make it
secure. You can and should run it with user permissions for most
functions, you can make it setgid for a group /var/log/messages is in
if all you need is to be able to read this file. Only the realtime
response mode with activated ipchains rule analysis needs superuser
permissions but you might also need them to write the PID file, for
actions in the response script and for binding the default status port.
However, you can configure fwlogwatch to drop root privileges as soon
as possible after allocating these resources (the notification and
response scripts will still be executed with user privileges and log
rotation might not work).
Boris Wesslowski <email@example.com>