What is a Computer Firewall?
Understand the basics of a computer firewall, the different types and how they work
Firewall Overview
In the broadest sense, a firewall is a mechanism that allows you to govern the traffic that goes through it, thereby allowing you to dictate what kind of traffic is allowed, or denied, between the firewalled infrastructure and the outer network. Firewall’s are one of the most common and most important devices for network security. They allow you to control access to your network and prevent unauthorized access.
To ensure that it’s working effectively, a firewall has to be configured properly. A poorly configured firewall will just become another vulnerability.
It is an essential component of IT security, the first line of defense from the network outside the protected perimeter.
Firewall Rules
A rule controls what kind of traffic is allowed, or denied.
For example, let’s take a look at a rule allowing inbound TCP traffic on port 8080 (Linux & Windows).
On Linux, the most common tool to manage the firewall is iptables, which will be used for the example below.
iptables -A INPUT -i eth0 -p tcp — dport 8080 -j ACCEPT
