What is firewall?

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A firewall is a system that is designed to prevent unauthorized access from entire private network. By filtering the information comes from the internet. Firewall blocks unwanted traffic and permits wanted traffic.

Firewall purposely creates a safely browser between a private network and the public internet because over the internet there is hackers and malware traffic tried to penetrate into private network to cause on. Firewall is the main component on network to prevent this.

Firewall is especially important to large organisation that has lot of computer and servers. We don’t want all those devices accessible to everyone on the internet. Hackers can comes totally disturbed that whole organisation that’s why we need firewall to protect them.

Firewall is used in computer network is very similar to firewall works in building structure that is word firewall came from. In a building structure provides a barrier when a fire on the one side of the building firewall is there to keep fire contained and keep spreading over from other side. Firewall is there to secure destroying entire building. If firewall is not there fire spreads over the other side and whole building will be destroyed. The same as the firewall works as a building structure.


Firewall stops harm full activities before it spreads into other side of firewall and cause harm to private network. Today hi-tech world firewall is very essential to every computer. Especially in business organisation to keep their network safe firewall works by filtering income data and it determines by a rows if allow to enter a network administrator. Administrator decides not only enter network but also what can leave the network.

This row allows or denies the permission. For example here we show rows and firewall access control list it shows list of IP address that have been allowed or denied by this firewall.

You can see traffic from IP address allowed to enter this network from the deny IP address try to enter into network other IP firewall other IP address are granted access because the rows allow them.


Firewall makes the rows based on the IP address but also based on domain names, protocols, programs, ports and keywords. The firewall rows controlling access by port numbers.             

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Lest say the rows have allowed incoming data that port number 80, 25, and 10 data using those ports has been given access network. Any incoming data using ports can pass through the firewall but also in the firewall rows can derived any data that using port numbers 23, 3389. Any incoming data using those port numbers the firewall will deney access and wont get pass the firewall.

There are two types of firewall. They are

  • Host based firewall
  • Network based firewall

Host based firewall

This is a software firewall. This firewall installed in a computer and that protects particular computer only nothing else.

In latest version of Microsoft operating system has a complete package of host based firewall.

In host based firewall we can purchase third party firewall and installed in computer. For example zone alarm. It is popular third party host based firewall alarm and also anti-virus programs built in host based firewall.

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Network based firewall

Network based firewall is a combination of hardware and software.

It operates on the network layer it is place between the private network and the public internet but host based network only protects the particular computer only but network based firewall protects the entire network. It does it through management rows that are applied to entire network. So any harmful activity stopped before it reaches the computer.

Network based firewall is a standalone product which is mainly used in large organisation and also built in the component router. Which is lot of smaller organisation is realis on. They also deployed on the server providers, cloud infrastructure lot of organisation used both network based firewall to protect network as a hole. They also used host based firewalls for their individual protection for their computer and severs by this ensures maximum protection because harmful data get passes through network firewall the host based firewall in each computer will be there to stop it.






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