/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
#
