What is a Firewall?
Firewall is a network security tool that monitors, filters and controls incoming and outgoing network traffic based on predefined rules. It can be built into hardware or software and it works by inspecting data packets to determine whether they should be allowed through. Firewalls are used to establish a barrier between trusted internal networks and untrusted external networks to prevent unauthorized access and the theft of sensitive information.
Like the walls around a castle or city, firewalls protect your computer and personal information by stopping outsiders from entering the premises. Firewalls are usually installed in the perimeter of a network and they are the most effective in protecting against attacks that exploit vulnerabilities in the host computers or the local Wi-Fi network.
There are two main types of firewalls: network-based and host-based. A network-based firewall is placed at a point in the network and it protects all computers on the “internal” side of the firewall from systems on the “external” side of the firewall, such as corporate servers from home systems or research systems from martketing systems.
The most common type of firewall is called a packet filtering firewall that examines individual data packets to see if they violate certain rules and if they do the firewall will block them. Firewall rules are created by a person who is familiar with networking, a firewall administrator, and they translate these policies into a series of technical statements that tell the hardware or software what to do.