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.
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 …