

Published on Jan 22, 2025
Prasanta R
The Role of Firewalls in Network Security: A Complete Guide
Network security is one of the greatest concerns of all people in 2025. Due to the excessive digitalization of our society, a lot of our sensitive information is present on a device of some kind. For example, your smartphone has your banking information.
This kind of information is very valuable because bad actors can use it for financial gain. That’s why protecting this data is critical. Today, the most common vector for cybercrime is the Internet. The internet connects virtually everyone in the world together, so bad actors have a lot of opportunities to attack unsecured networks and devices.
As such, network security is critical. Today, we will be discussing the first line of defense in network security, aka a firewall.
What is a Firewall?
A firewall is either a software or hardware security measure that acts as a barrier between two networks. Typically, one of the networks is a trusted internal network, and one is an untrusted external network.
A common example is your home network. The home network is trusted, but the internet (an external network) is not. So, a firewall is set up between them to protect the internal network from the external one.
At its core, a firewall checks incoming traffic from an external network to see if it has anything suspicious. If suspicious elements are found, the traffic will be blocked from entering the internal network.
There are many different types of firewalls, and they all work in different ways. Let’s check out some of the more well-known types and see how they work.
Types of Firewalls and Their Role in Network Security
- Packet Filtering Firewall
Packets filtering firewall is the most basic type of firewall. Packet filtering was developed in the 1980s. It relies on inspecting every single packet trying to enter the internal network.
The packets are deemed okay or suspicious based on their source and destination as well as the protocols used. This includes the ports that they are directed to. A simple packet-filtering firewall has the following advantages.
- It is fast (does not hold up network traffic)
- It is simple to set up.
- It is efficient.
However, all of these benefits come with a cost. Such a simple firewall cannot detect sophisticated and complex attacks. One of the main reasons is that it does not have stateful inspection.
We will learn about stateful inspection in the next heading.
- Stateful Inspection Firewall
Stateful inspection firewalls are an upgrade of the packet filtering firewall. They are able to inspect packets and make decisions based on the context of the network traffic.
Basically, the firewall is aware when a packet signals the start of a new correspondence or if it is part of an ongoing session. A stateful firewall will create temporary rules so that it can let through packets of an authorized session.
So, it only checks packets that are starting a new session. This way, efficiency, and accuracy are balanced very well.
- Application Layer Firewall
Packet filtering and stateful inspection are layer three (OSI Model) firewalls. There are some firewalls that work on layer two or the application layer. They are aptly named application layer firewalls.
Application layer filtering is more sophisticated than packet filtering. It actually checks the contents of the packet to see if they are malicious or not.
Naturally, they have to be stateful inspections as context is necessary to know whether the payload will result in harm or not. This is the kind of firewall that can detect harmful content in emails, download files, and messages.
- Next-Generation Firewall
Next-Gen Firewalls (NGFW) are the latest type of firewalls. They can do all of the things that other firewalls can and more. For a firewall to be classified as an NGFW, it must have the following properties.
- Stateful inspection capability
- Payload inspection
- Application awareness and control
- Threat intelligence sources
- Intrusion prevention
- Room for upgrades
NGFWs are so good they can use their threat intelligence sources and IP location capabilities to determine if traffic is malicious or not.
Typically, such a firewall is specifically run on hardware. However, you can use a virtual machine to run it in software form as well. Whichever is more convenient for you.
Firewall Deployment Types
Most firewalls can be deployed via special hardware, or they can run through software.
If your network has a special router just for running a firewall, then it will be considered a hardware firewall. Similarly, if the firewall is not on its own device but running on your computer/smartphone, then it's considered a software firewall.
Software firewalls are great at securing a single device’s network connection. Personal desktop computers and laptops often have a built-in firewall in their operating system.
Hardware firewalls are great at securing an entire internal network. They can be connected to the internet access point so that all the incoming traffic can be scanned.
There is a third type called a cloud firewall. Cloud firewalls are used to secure cloud environments. Since cloud applications are not present on your own network, your firewall can’t secure them. So, you need to get a cloud firewall to secure them.
Conclusion
So, there you have it, the role of firewalls in network security. They are the first line of defense, and their role is to prevent malware, viruses, and otherwise malicious traffic from entering a network.
Modern firewalls are continuously evolving to battle new threats. It is important that you secure your networks with firewalls; otherwise, you may risk compromising your network.