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#!/bin/sh

EXTERNAL_INTERFACE="ra0"
LOOPBACK_INTERFACE="lo"

LAN_BCAST_ADDRESS="192.168.2.255"
# Adjust LAN_BCAST_ADDRESS to suit your network

# Get the IP Addresses for the network cards
IPADDR=`/sbin/ifconfig $EXTERNAL_INTERFACE | grep -i "addr:" | cut -f2 -d: | cut -f1 -d " "`
LOCALHOST_IP="127.0.0.1/32"


##########

echo "Starting Firewalling... "
iptables --flush
iptables --delete-chain
iptables --zero

########## Set default policies
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP
iptables -A INPUT -i $LOOPBACK_INTERFACE -j ACCEPT
iptables -A OUTPUT -o $LOOPBACK_INTERFACE -j ACCEPT

########## Create Seperate Chains for ICMP, TCP and UDP to traverse
echo "Create Seperate Chains for ICMP, TCP and UDP to traverse..."
iptables --new icmp_packets
iptables --new tcp_packets
iptables --new udpincoming_packets

########## The Allowed Chain for TCP connections
echo "The Allowed Chain for TCP connections "
iptables -N allowed
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 (Internet Control Message Protocol)
echo "ICMP rules (Internet Control Message Protocol) "
iptables -A icmp_packets -p ICMP -s 0/0 --icmp-type 0 -j ACCEPT
iptables -A icmp_packets -p ICMP -s 0/0 --icmp-type 3 -j ACCEPT
iptables -A icmp_packets -p ICMP -s 0/0 --icmp-type 5 -j ACCEPT
iptables -A icmp_packets -p ICMP -s 0/0 --icmp-type 11 -j ACCEPT

########## TCP rules (Transmission Control Protocol)
echo "TCP rules (Transmission Control Protocol) "
### FTP port
#iptables -A tcp_packets -p TCP -s 0/0 --dport 21 -j allowed

### SSH port
iptables -A tcp_packets -p TCP -s 0/0 --dport 22 -j allowed

### SMTP Mail Server port
#iptables -A tcp_packets -p TCP -s 0/0 --dport 25 -j allowed

### HTTP port
iptables -A tcp_packets -p TCP -s 0/0 --dport 80 -j allowed

### POP3 port
#iptables -A tcp_packets -p TCP -s 0/0 --dport 110 -j allowed

### IRC port
#iptables -A tcp_packets -p TCP -s 0/0 --dport 113 -j allowed

### IMAP port
#iptables -A tcp_packets -p TCP -s 0/0 --dport 143 -j allowed

### No-ip DNS services port
#iptables -A tcp_packets -p TCP -s 0/0 --dport 8245 -j allowed

########## UDP ports (User Datagram Protocol)
echo "UDP ports (User Datagram Protocol) "
iptables -A udpincoming_packets -p UDP -s 0/0 --source-port 53 -j ACCEPT
iptables -A udpincoming_packets -p UDP -s 0/0 --source-port 123 -j ACCEPT
iptables -A udpincoming_packets -p UDP -s 0/0 --source-port 2074 -j ACCEPT
iptables -A udpincoming_packets -p UDP -s 0/0 --source-port 4000 -j ACCEPT
iptables -A udpincoming_packets -p UDP -s 0/0 --source-port 143 -j ACCEPT

########## INPUT chain # Establish the basic Input chain
##########	and filter the packets onto the correct chains.
echo "INPUT chain # Establish the basic Input chain "
iptables -A INPUT -p ICMP -i $LAN_INTERFACE_1 -j icmp_packets
iptables -A INPUT -p TCP -i $LAN_INTERFACE_1 -j tcp_packets
iptables -A INPUT -p UDP -i $LAN_INTERFACE_1 -j udpincoming_packets

iptables -A INPUT -p ALL -i $LAN_INTERFACE_1 -d $LAN_BCAST_ADDRESS -j ACCEPT
iptables -A INPUT -p ALL -d $LOCALHOST_IP -j ACCEPT
iptables -A INPUT -p ALL -d $LAN_IPADDR -j ACCEPT
iptables -A INPUT -p ALL -d $IPADDR -m state --state ESTABLISHED,RELATED -j ACCEPT

########## ENABLE TO LOG ERRORS
echo "ENABLE TO LOG ERRORS "
iptables -A INPUT -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix "IPT INPUT packet died: "

########## OUTPUT chain # Establish the basic Output chain
##########	and filter them onto the correct chain

iptables -A OUTPUT -p ALL -s $LOCALHOST_IP -j ACCEPT
iptables -A OUTPUT -p ALL -s $LAN_IPADDR -j ACCEPT
iptables -A OUTPUT -p ALL -s $IPADDR -j ACCEPT

########## ENABLE TO LOG ERRORS
iptables -A OUTPUT -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix "IPT OUTPUT packet died: