firewall

What is a Firewall

Jeba_Singh_P August 28, 2019 Leave a Reply

What is a Firewall ?


Most commonly you would have came across a term call as a firewall while using internet.Let's see what does it really mean.

  • A firewall can either be a hardware or a software.
  • It can be called as a network security system that monitors and controls traffic to a private network based on some defined security rules.
  • It blocks unwanted traffic and permits wanted traffics.
So what is traffic here?
  • we commonly define traffic as the amount of data moving across a network at a given point of time.
In today's world every network(office,business) should have a firewall to keep their network safe.

  • The one way that the firewall controls the flow of traffic in to and out of the network is by Access Control List(ACL).
  • a ACL consist of the list of members who can access the network through the firewall.
  • Example:

                    A firewall has the following ACL
                        165.43.99.03 --> Allow
                        172.15.16.10 -->Deny
                        45.90.172.66 --> Allow

  • Then only the IP addresses 165.43.99.03 and 45.90.172.66 can access and pass through this firewall
  • When ever 172.15.16.10 tries to access the firewall it blocks its request.
Some firewall comes with implicit deny rules.for example a firewall can allow only access to port 80 i.e. the websites.so we cannot access other things such as ftp , smtp etc..
  • one of the example of the firewall is the Host based fire wall.
  • It is a software based firewall.
  • It is installed on a computer only and it protects that computer alone.
  • Later versions of windows comes with host based firewall called as windows firewall.we can enable it or disable it as per our need.
  • we can also install third party firewall softwares . such as Glash wire, zonealarm , peerblock etc..


  • An another example of firewall is the network based firewall .
  • It is a combination of hardware and software.
  • It protects an entire network.





A real time application of firewall is that we know that some websites are not allowed in some countries .
  • In this case all the ISP who are serving the internet to the users use a fire wall to block the users in that particular country from accessing the list of sites.

note: you can read my previous posts at  https://iamafutureprogrammer.blogspot.com/

If you have any queries ask in the comment section below.......Thank you ....


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