What is a Firewall? Explained, and It’s Types

what is a firewall

What is a firewall, how does it work, what are these types? Deep discussion on all the topics regarding their advantages and disadvantages etc.

The world is made up of two things. Only then, when the first network virus spread on the network of Creeper ARPANET, an antivirus named Reaper was created.

Since the invention of the Internet, a lot of research has been done about security. As a result of which new equipment was also created.

One of these is a Firewall. Which nowadays comes inbuilt in all good modems, routers, etc.

Instead, it is the most important of any networking device. It comes in Windows only through Inbuilt. Due to these reasons, it is called First Line Security.

What is a firewall

A firewall is a technique for making the network of computer systems secure.

It is used to filter the network. That is, it is used to spread unauthorized things in any network. These things can be like viruses, Trojans, spyware, malicious links, etc.

Firewalls (Hardware & Software)

Firewall technology exists in both Software and Hardware types. It can be used by installing its Antivirus software program on the computer. Almost all good antivirus apps work as firewalls.

It can also be set up on your network by purchasing a hardware device. We learn about the companies providing hardware firewalls devices below.

How a firewall works

As the name suggests, it acts as a security wall. By which the user requested data packet has to be filtered. We can understand this easily.

Suppose there are one or several computers in an office/house. They are connected to each other through a network such as wifi. Such a network is called a private network.

Whenever a user connects to a public network such as the Internet through computers or other devices in his home or office, there is always the possibility of accessing all the harmful software spread on the Internet on his computer.

The firewall acts as a security wall between these private and public networks. It protects both sides of the network. A virus from the user’s computer to the Internet prevents it from going on and protects the Internet from damage to the user’s computer.

Therefore it is called a two-way protection provider.

Whenever a request is sent by the user over the Internet, that request first reaches the Firewall device or software.

Firewall remembers the data packet for that request and the network ID that accompanies it. When his result comes back from the Internet to his public network, then the firewall intercepts it and checks the data packet and checks the Trusted rules and the user’s allowance. Also, after checking third party apps, viruses, etc., they then let them come into the private network.

In this way, the Firewall protects our network from unauthorized third-party software.

Advantage & Disadvantage of Firewall

We have learned all the features of Firewall but it also has some disadvantages. If you do not use Firewall Security of a good company, then it can also slow the system down a bit by using more resources of your system like CPU, RAM, etc.

Firewalls are powerful security tools but they have some limitations. These protect you from an external network, but if a floppy disk or other internal media in your computer, viruses, malware, or any harmful software from Backdoor reaches the system, then Firewalls cannot protect you here.

At the same time, if you are using a software firewall, then it will only protect the computer in which the firewall is installed. Software firewalls are used as antivirus in most PCs.

Thus firewall installation becomes necessary in all systems. Yes, if you use Windows, then it comes inbuilt from the company. The user can also configure it according to his own.

On the other hand, if you use a hardware device, it will protect multiple systems simultaneously. But for better performance and security, it is best to install a firewall device between every two computers.

Types of Firewalls

The firewall is divided into five parts based on its function. Which can be used keeping in mind the need and improvement.

They work on different theories but the objective is network security.

  • Packet-filtering firewalls
  • Stateful inspection firewalls
  • Circuit-level gateways
  • Application-level gateways
  • Next-gen firewalls

1. Packet-filtering firewalls

This theory or program is the oldest firewall technique. Which tests outgoing and incoming data packets based on its headers, IP addresses, ports, etc.

2. Stateful inspection firewalls

This technology is much better and advanced than the above technology as it provides the security of the application layer.

This allows data to come into the network by examining data packets based on its ports, destination sources, etc., not on the basis of the packet’s header but on the basis of the packet’s contents.

This technique performs data filtering not only on the Administrator’s defined rules of packet data but also on the basis of data that have already been passed from the network.

This technique can reduce the speed of data flow slightly.

3. Circuit-level gateways

This technology works like a Proxy and provides circuit-level filtering to traffic, which is roughly equivalent to the application layer.

This transmission control protocol (TCP) provides security by verifying the handshake. It does not filter the data itself. It only verifies the source of data.

Therefore, if the source of the data is valid and the data packet contains malware, then it will pass in the system. Which can cause computers to be infected?

However, once the TCP / UDP connections are established, the data flow without a double-check

4. Application-level gateways

These provide the best security of network connections among security media operating on firewall technology.

It acts as a Proxy. Like in a VPN service, our data packet is received through the VPN proxy server. Similarly, it establishes a proxy server connection between the client and the destination. In this way, the user first comes to the data packet on the proxy server and then comes to the user from the proxy server.

In this way, the user’s system and its network ID remain secure. However, computer resources are most used in their operation.

5. Next-Gen firewalls

It secures systems with the most advanced and better Capability in Firewall Security Systems. These apply all the above-mentioned techniques like State Inspection, Filtering of data, etc.

These secure the security of the system in new and smart ways. Applies a variety of security mechanisms to data packets to ensure data security. These act like a signature-based engine with no possibility of Intrusion. All of the earlier firewalls contain good technology.

Best Hardware & Software Firewalls

Firewalls can be used for everything from personal to company and Organizations.
Whereas firewalls systems come at slightly lower prices for personal use, while those for larger networks are expensive.

Many companies have launched firewall software and hardware devices in the market.
Some of the best companies are:

  • Cisco
  • McAfee
  • Check Point
  • Forti Gate
  • Palo Alto networks
  • Cyberoam
  • Sonicwall

Devices of these companies are good.


In this post, we have learned what is a Firewall is and how it works. The conclusion of this post is that in today’s era, the firewall is very important. But at the same time take this caution whenever you choose Use Trusted company’s Firewall service. You can also read it here in English for more information.

Friends! We hope that this post of yours has proved useful to you. If you have any suggestions for us, do let us know in the comments. Also, share this post on your friends and social media.


Roshan Mehta

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