Swatch

the active log file monitoring tool. Swatch started out as the "simple watchdog" for activly monitoring log files produced by UNIX's syslog facility. It has since been evolving into a utility that can monitor just about any type of log.

http://swatch.sourceforge.net/

Problem

Scan-Attacks on FTP-Server

Apr 13 05:25:00 mygretchen pure-ftpd: (?@88.198.15.174) [INFO] New connection from 88.198.15.174
Apr 13 05:25:00 mygretchen pure-ftpd: (?@88.198.15.174) [WARNING] Sorry, cleartext sessions are not accepted on this server. Please reconnect using SSL/TLS security mechanisms.

Solution

Monitor syslog and drop IP-Address via Shorewall (iptables)

Configuration

/etc/init.d/swatch

#! /bin/sh
### BEGIN INIT INFO
# Provides:          skeleton
# Required-Start:    $local_fs $remote_fs
# Required-Stop:     $local_fs $remote_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Example initscript
# Description:       This file should be used to construct scripts to be
#                    placed in /etc/init.d.
### END INIT INFO

# Author: Jonathan Tietz
#
# Please remove the "Author" lines above and replace them
# with your own name if you copy and modify this script.

# Do NOT "set -e"

# PATH should only include /usr/* if it runs after the mountnfs.sh script
PATH=/sbin:/usr/sbin:/bin:/usr/bin
DESC="Swatch LogFile-Monitor"
NAME=swatch
DAEMON=/usr/bin/$NAME
DAEMON_ARGS="--daemon --awk-field-syntax --config-file=/etc/swatch/swatch.conf"
#--tail-args=\'--follow=name --lines=1\'
PIDFILE=/var/run/$NAME.pid
SCRIPTNAME=/etc/init.d/$NAME

# Exit if the package is not installed
[ -x "$DAEMON" ] || exit 0

# Read configuration variable file if it is present
[ -r /etc/default/$NAME ] && . /etc/default/$NAME

# Load the VERBOSE setting and other rcS variables
. /lib/init/vars.sh

# Define LSB log_* functions.
# Depend on lsb-base (>= 3.0-6) to ensure that this file is present.
. /lib/lsb/init-functions

#
# Function that starts the daemon/service
#
do_start()
{
# Return
#   0 if daemon has been started
#   1 if daemon was already running
#   2 if daemon could not be started
#start-stop-daemon --start --quiet --pidfile $PIDFILE --exec $DAEMON --test > /dev/null \
#       || return 1
#start-stop-daemon --start --quiet --pidfile $PIDFILE --exec $DAEMON -- \
#       $DAEMON_ARGS \
#       || return 2
# Add code here, if necessary, that waits for the process to be ready
# to handle requests from services started subsequently which depend
# on this one.  As a last resort, sleep for some time.
if [ ! -d ${SWATCH_SCRIPTDIR} ]; then
mkdir ${SWATCH_SCRIPTDIR}
fi

swatch --script-dir=${SWATCH_SCRIPTDIR} \
--tail-file=${SWATCH_TAILFILE} \
--config-file=/etc/swatch/swatch.conf \
--pid-file=/var/run/swatch.pid \
--tail-args='--follow=name --lines=1' \
--daemon \
>> /var/log/swatch.log \
2>> /var/log/swatch-err.log
#       --tail-args='--follow=name --lines=1'
#--tail-args="${SWATCH_TAILARGS}" \

}

#
# Function that stops the daemon/service
#
do_stop()
{
# Return
#   0 if daemon has been stopped
#   1 if daemon was already stopped
#   2 if daemon could not be stopped
#   other if a failure occurred
#start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PIDFILE --name $NAME
kill -9 `cat /var/run/swatch.pid`
RETVAL="$?"
[ "$RETVAL" = 2 ] && return 2
# Wait for children to finish too if this is a daemon that forks
# and if the daemon is only ever run from this initscript.
# If the above conditions are not satisfied then add some other code
# that waits for the process to drop all resources that could be
# needed by services started subsequently.  A last resort is to
# sleep for some time.
start-stop-daemon --stop --quiet --oknodo --retry=0/30/KILL/5 --exec $DAEMON
[ "$?" = 2 ] && return 2
# Many daemons don't delete their pidfiles when they exit.
rm -f $PIDFILE
return "$RETVAL"
}

#
# Function that sends a SIGHUP to the daemon/service
#
do_reload() {
#
# If the daemon can reload its configuration without
# restarting (for example, when it is sent a SIGHUP),
# then implement that here.
#
start-stop-daemon --stop --signal 1 --quiet --pidfile $PIDFILE --name $NAME
return 0
}

case "$1" in
start)
[ "$VERBOSE" != no ] && log_daemon_msg "Starting $DESC" "$NAME"
do_start
case "$?" in
0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
2) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
esac
;;
stop)
[ "$VERBOSE" != no ] && log_daemon_msg "Stopping $DESC" "$NAME"
do_stop
case "$?" in
0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
2) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
esac
;;
#reload|force-reload)
#
# If do_reload() is not implemented then leave this commented out
# and leave 'force-reload' as an alias for 'restart'.
#
#log_daemon_msg "Reloading $DESC" "$NAME"
#do_reload
#log_end_msg $?
#;;
restart|force-reload)
#
# If the "reload" option is implemented then remove the
# 'force-reload' alias
#
log_daemon_msg "Restarting $DESC" "$NAME"
do_stop
case "$?" in
0|1)
do_start
case "$?" in
0) log_end_msg 0 ;;
1) log_end_msg 1 ;; # Old process is still running
*) log_end_msg 1 ;; # Failed to start
esac
;;
*)
# Failed to stop
log_end_msg 1
;;
esac
;;
*)
#echo "Usage: $SCRIPTNAME {start|stop|restart|reload|force-reload}" >&2
echo "Usage: $SCRIPTNAME {start|stop|restart|force-reload}" >&2
exit 3
;;
esac

:

/etc/swatch/swatch.conf

in a time frame of 20 sec. (seconds) if we have 20 matches (count) of "watchfor" do the action (exec), then ignore (type)

# Global swatch filter file

# Invalid FTP Login Attempts
#Apr  5 01:12:58 mygretchen pure-ftpd: (?@217.229.137.69) [WARNING] Sorry, cleartext sessions are not accepted on this server. Please reconnect using SSL/TLS security mechanisms.
watchfor /(.*)pure-ftpd: (.*)\@(.*)\)( \[WARNING\] Sorry, cleartext sessions are not accepted)(.*)/
        threshold track_by=$3,type=both,count=20,seconds=20
        mail=sadmin@mygretchen.de,subject="FTP:\ Invalid\ User\ Access-IPTables\ Rule\ Added"
        exec "/etc/swatch/scripts/shorewall.sh $3"
        #exec echo $3 >> /var/log/swatch_ftp.log

/etc/swatch/scripts/shorewall.sh

#!/bin/sh
IP=`host $1|awk {'print $3'}`
#echo $IP

if [ "x$IP" != "x" ]; then
/sbin/shorewall drop $IP
mail sadmin -s shorewall<<END
$IP was dropped
END
else
IP=`host $1|grep Address|awk {'print $2'}`
if [ "x$IP" != "x" ]; then
/sbin/shorewall drop $IP
mail sadmin -s shorewall<<END
$IP was dropped
END
else
mail sadmin -s shorewall<<END
Problem to drop $1: $IP
END
fi
fi

Links

http://gentoo-wiki.com/HOWTO_Protect_SSHD_with_Swatch