Installation

Simple, if it’s not installed already then run the following commands

sudo apt-get install iptables
sudo /etc/init.d/iptables start

The safest and best way of configuring iptables, in my opinion, is to have two files. The first is a temporary/test set that you will save to first, the second is the actual rule set that will be loaded to iptables.

Configuration

So, first we’ll create an empty temp rules file

sudo touch /etc/iptables.temp.rules

Add some simple rules to it:

*filter
# Allows all loopback traffic and drop all traffic to 127/8 that doesn't use lo

-A INPUT -i lo -j ACCEPT
-A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT

# Accepts all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allows all outbound traffic
-A OUTPUT -j ACCEPT

#SSH
-A INPUT -p tcp -m …