Firewall in Computer

A firewall in computer is a network security device that protects your device from the external network. Let us understand this with the help of a real-life example. You might have seen that before anyone check-in to the airport they are thoroughly checked to ensure that they do not carry anything that is prohibited at the airport premises. This is to ensure the security of the crowd present at the airport and even of the airplane that has to take off.

Similarly, the firewall filters out all the unwanted traffic coming from the external network. In this context, we will explore firewalls in detail, we will try to understand how it works, how many types of firewalls are there, and many interesting facts about firewall.

Firewall in Computer

  1. What is Firewall?
  2. How Does a Firewall Work?
  3. Types of Firewalls
  4. Network Firewall
  5. Advantages and Disadvantages

What is Firewall?

A firewall is a network security device that filters out the incoming and outgoing traffic coming to and from your device. It restricts unwanted access to the private data present in your computer by blocking some specific traffic that violates a set of defined security rules.

Firewall in Computer

A firewall is installed between the internal network and the external network i.e., the internet. The main objective of a firewall is to create the first line of defense by restricting malicious traffic and allowing non-threatening traffic in order to protect your computer from external attacks.

Firewall in Computer 2

A firewall could either be hardware, software, or an implementation of both.

How Does a Firewall Work?

Now we know that we require a firewall to protect our devices from malicious traffic. Let us try to understand how it works. For that, we need to understand the structure of the web-Based network.

Network protection

We can classify a web-based network into the:

External Network: It is the global/public network that we refer to as the internet.

Internal Network: It is a private network that can be a home network, corporate intranet, and other closed networks.

So, the main purpose of a firewall is to monitor the data traffic between the external and internal networks and restrict specific traffic based on predefined rules. It only allows that incoming traffic from the external network into the internal network for which it has been configured.

Types of Firewalls

The firewall in computer can be implemented in hardware, software, or a combination of both. Each of its implementations has an important purpose. The hardware firewall is a physical implementation of a firewall such as in the form of a router. The hardware firewall is placed between the internal network and the gateway.

The software firewall is a logical implementation of a firewall and functions through the ports and applications.

With the evolving technology, nowadays firewalls can be implemented with the cloud as Firewall as a Service (FaaS).

We can differentiate firewalls on the basis of their structure, their functionalities, the size of the network they secure, and the level of security they provide.

1. Packet Filtering Firewall

The packet filtering firewall filter out packets from trusted networks only. Now how does it validate that the packet has arrived from the trusted network? Well, the packet filtering firewall verifies each packet against a set of rules. These rules let the firewall validate the IP addresses of the packet i.e., against the allowed IP addresses, it also validates the type of packet, port number, and other attributes of the packet protocol header.

The packets that don’t get validated against the set of rules are discarded and are not allowed to enter the network. The drawback of a packet-filtering firewall is that it only checks the attributes of the packet header only. It never verifies the data/payload of the packet. What if the data inside the packet is malicious? That’s why this is not the ideal firewall for every network.

2. Proxy Service Firewall

Proxy service firewall is also referred application-level gateway. It is considered more secure than a packet-filtering firewall. Let’s see why?

The proxy service firewall validates the data/ payload along with the header of the packet. Here, the proxy firewall is placed between the client and the internet. Now whenever the client makes a request to the web server (internet) the request does not directly reach the web server instead the request first reaches the proxy server.

The proxy server then forwards this request to a web server. The web server generates a response for the request and then forwards it to the proxy server. The proxy server validates the response from the web server and forwards it to the corresponding client.

In this scenario, both the web server and client feel that they are directly communicating with each other and there is no firewall.

But there is a firewall that acts as a proxy server for the client. It validates both requests and responses.

Network Firewalls

Network firewalls are the security devices that are installed between the internet and private network. The network firewalls are specially for intranets. It is the firewall policies that decide what kind of traffic should enter the network and what traffic would be blocked.

Network firewalls achieve the security of the private network by examining each incoming traffic and rejecting one that fails to meet the policies of the network firewall. A network firewall is configured to allow users to access the resources they want parallelly it also blocks malicious content from entering the network and also prevents hackers from trying to access the protected network.

Advantages and Disadvantages of Firewall in Computer


  1. It monitors the incoming and outgoing traffic passing through it.
  2. It provides protection against malicious programs from entering the network.
  3. The firewall also prevents hackers from accessing the firewall-protected network.
  4. A firewall can be configured to decide what kind of traffic is allowed into the network.


  1. The cost of hardware depends on its type. The hardware firewall is quite costly as it requires installation and maintenance costs. However, the software firewall does not require must investment and is easy to deploy.
  2. The firewall policies can restrict its users from accessing a large number of resources that can be essential for their organizational operation.
  3. A firewall monitors the incoming the outgoing traffic from the network and this requires time, slowing down the network performance.
  4. The malware is evolving nearly every second and they can enter your network even from a trusted connection, and the traffic from this connection is not blocked by the firewall.

So we can conclude that a firewall in computer can keep your network ad connected devices safe from malware if deployed and maintained properly.

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