iptables-rules

#!/bin/bash

# Set the default policies to allow everything while we set up new rules
# Prevents cutting yourself off when running from remote SSH
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT

# Flush any existing rules, leaving just the defaults
iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X

# Open port 22 only for incoming SSH connections
iptables -A INPUT -p tcp --dport 22 -j ACCEPT

# accept any localhost (loopback) calls
iptables -A INPUT -i lo -j ACCEPT

# allow any existing connection to remain
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# reset the default policies to stop all incoming and forward requests
iptables -P INPUT DROP
iptables -P FORWARD DROP

# accept any outbound requests from this server
iptables -P OUTPUT ACCEPT