Basics of Firewalls in Linux

What is a Firewall?

Just as a firewall in a building attempts to prevent a fire from spreading, a computer firewall attempts to prevent malicious or unwanted software from spreading to your computer from the network.

A Firewall also helps to prevent unauthorized users from accessing your computer.

In a default Linux installation, a firewall exists between your computer or network and any un-trusted networks, for example the Internet. It determines which services on your computer remote users can access. A properly configured firewall can greatly increase the security of your system.

It is strongly recommended that you configure a firewall for any system with an Internet connection properly, to secure your computer from malicious software and external attackers.