Adding a Firewall

[ghost]

I suggest adding a firewall and using UFW .. its ever so simple to install and configure

Install UFW firewall

sudo apt-get install ufw

Configure the firewall to deny incoming connections by default then allow SSH and limit to prevent dictionary attacks, and then to also open the ports used by Bitcoin

sudo ufw default deny incoming
sudo ufw allow ssh/tcp
sudo ufw limit ssh/tcp
sudo ufw allow 8333/tcp
sudo ufw allow 8332/tcp
sudo ufw enable
sudo reboot

You can check your firewall's status by entering the following command:

sudo ufw status

It should say active.