set_up_iptables.sh

#!/bin/bash

# remove existing rules and set defaults
iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X
iptables -P INPUT DROP
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT

#nat
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

#filter
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -p icmp -m icmp --icmp-type any -j ACCEPT
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -i wlan0 -m state --state NEW -j ACCEPT
iptables -A INPUT -p tcp -m tcp ! --tcp-flags FIN,SYN,RST,ACK SYN -m state --state NEW -j DROP
iptables -A INPUT -f -j DROP
iptables -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,SYN,RST,PSH,ACK,URG -j DROP
iptables -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
iptables -A INPUT -i wlan0 -p udp -m udp --sport 53 -j ACCEPT
iptables -A INPUT -j LOG --log-prefix "IPTABLES Dropped: " --log-level 7
iptables -A INPUT -j DROP