What is firewall? How it works?

Firewall

 A firewall is a network security system in computer. It watches and controls incoming and outgoing network traffic based on prearranged security roles. Firewall creates a barrier between a trusted internal network and untrusted external network, such as the internet.

It protect a network or system from unauthorized access with a firewall.

How firewall works?

A firewall is a program or hardware device.  Information comes through the internet connection into your private network or computer system. Firewall filters it. 
If an incoming packet of information is indicated by the filters, it is not allowed through.

Categories of firewall

Firewalls are often categorized as:

• Network firewalls
• Host-based firewall

Network Firewalls:

It is the type of firewalls that filters traffic between two or more networks and run on network hardware.


Host-based Firewall:

Host-based firewalls run on host computers and control network traffic in and out of those two machines.