DMZ_DNS_IP="192.168.1.3"

DMZ_IP="192.168.1.1"

DMZ_IFACE="eth2"

#

# 1.4 Localhost Configuration.

#

LO_IFACE="lo"

LO_IP="127.0.0.1"

#

# 1.5 IPTables Configuration.

#

IPTABLES="/usr/sbin/iptables"

#

# 1.6 Other Configuration.

#

###########################################################################

#

# 2. Module loading.

#

#

# Needed to initially load modules

#

/sbin/depmod -a

#

# 2.1 Required modules

#

/sbin/modprobe ip_tables

/sbin/modprobe ip_conntrack

/sbin/modprobe iptable_filter

/sbin/modprobe iptable_mangle

/sbin/modprobe iptable_nat

/sbin/modprobe ipt_LOG

/sbin/modprobe ipt_limit

/sbin/modprobe ipt_state

#

# 2.2 Non-Required modules

#

#/sbin/modprobe ipt_owner

#/sbin/modprobe ipt_REJECT

#/sbin/modprobe ipt_MASQUERADE

#/sbin/modprobe ip_conntrack_ftp

#/sbin/modprobe ip_conntrack_irc

#/sbin/modprobe ip_nat_ftp

#/sbin/modprobe ip_nat_irc

###########################################################################

#

# 3. /proc set up.

#

#

# 3.1 Required proc configuration

#

echo "1" > /proc/sys/net/ipv4/ip_forward

#

# 3.2 Non-Required proc configuration

#

#echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter

#echo "1" > /proc/sys/net/ipv4/conf/all/proxy_arp

#echo "1" > /proc/sys/net/ipv4/ip_dynaddr

###########################################################################

#

# 4. rules set up.

#

######

# 4.1 Filter table

#

#

# 4.1.1 Set policies

#

$IPTABLES -P INPUT DROP

$IPTABLES -P OUTPUT DROP

$IPTABLES -P FORWARD DROP

#

# 4.1.2 Create userspecified chains

#

#

# Create chain for bad tcp packets

#

$IPTABLES -N bad_tcp_packets

#

# Create separate chains for ICMP, TCP and UDP to traverse

#

$IPTABLES -N allowed

$IPTABLES -N icmp_packets

#

# 4.1.3 Create content in userspecified chains

#

#

# bad_tcp_packets chain

#

$IPTABLES -A bad_tcp_packets -p tcp –tcp-flags SYN,ACK SYN,ACK \

–m state –state NEW -j REJECT –reject-with tcp-reset

$IPTABLES -A bad_tcp_packets -p tcp ! –syn -m state –state NEW -j LOG \

–log-prefix «New not syn:»

$IPTABLES -A bad_tcp_packets -p tcp ! –syn -m state –state NEW -j DROP

#

# allowed chain

#

$IPTABLES -A allowed -p TCP –syn -j ACCEPT

$IPTABLES -A allowed -p TCP -m state –state ESTABLISHED,RELATED -j ACCEPT

$IPTABLES -A allowed -p TCP -j DROP

#

# ICMP rules

#

# Changed rules totally

$IPTABLES -A icmp_packets -p ICMP -s 0/0 –icmp-type 8 -j ACCEPT

$IPTABLES -A icmp_packets -p ICMP -s 0/0 –icmp-type 11 -j ACCEPT

#

# 4.1.4 INPUT chain

#

#

# Bad TCP packets we don't want

#

$IPTABLES -A INPUT -p tcp -j bad_tcp_packets

#

# Packets from the Internet to this box

#

$IPTABLES -A INPUT -p ICMP -i $INET_IFACE -j icmp_packets

#

# Packets from LAN, DMZ or LOCALHOST

#

#

# From DMZ Interface to DMZ firewall IP

#

$IPTABLES -A INPUT -p ALL -i $DMZ_IFACE -d $DMZ_IP -j ACCEPT