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What is a Firewall? 5 Types and Examples You Need to Know

By Tibor Moes / January 2023

What is a Firewall? Types and Examples You Need to Know

What is a Firewall?

Cybersecurity is one of the top concerns of the digital age for both personal and corporate users. There are so many ways someone can gain unauthorized access to files, databases, networks, and private devices, it’s overwhelming.

Because of the increasing risks and rise in cybercrime, more users are learning how to beef up their cybersecurity protocols. One of these tools is the well-known Firewall. Despite being commonly used, not everyone understands what it is, what it does, or how to get the most out of it.

Summary: A firewall can monitor and filter incoming and outgoing traffic, and prevent unauthorized access to a device or network. Firewalls come in many versions, from software to hardware, and from standardized to deeply customizable. Which is best for you, will depend on what you are protecting. A single Windows PC will have very different requirements from an entire corporate network.

Tip: The digital world is a dangerous place. Luckily, modern antivirus software include powerful firewalls and Virtual Private Networks to keep you safe. Invest in your cybersecurity before it’s too late.

How Firewalls Work

A firewall can have multiple delivery methods. As such, you have software firewall, hardware firewall, and cloud firewall options. But regardless of the delivery method and firewall functionality, every firewall accomplishes the same tasks, more or less.

Firewalls are installed on a hardware or software level to detect, monitor, and filter out malicious traffic. Depending on its complexity, scope, and location, a firewall may protect entire networks or individual devices.

Every firewall can be customized to check network traffic against specific rules.

If you have ever installed a new app or game, you were probably asked if you want to allow it to pass through the firewall. You could trust an application to run but rule against sending or receiving packets over the internet. Such firewall examples are prevalent on Windows computers, whether you’re using a built-in or aftermarket firewall application.

Similar examples are instances when certain IP addresses are banned and can’t be accessed. This may include streaming platforms, websites, servers, online apps, etc.

But what do firewalls check in the data packets? Every data packet is made of a header and payload. These components contain control information and data chunks. A header can give the firewall information about the sender and receiver involved in a data transfer.

If that information doesn’t contain anything forbidden by the firewall’s rule set, it will be able to pass.

Firewall Types You Need to Know

Although firewalls can be deployed in the cloud, digitally, or on a hardware level, they can be broken down into five distinct categories based on the techniques used.

Packet-Filtering Firewalls

Firewalls have been around for at least three decades. The earliest iterations were simply called packet filters. For the most part, this has remained the primary function of modern firewalls.

A packet-filtering firewall is aptly described. It’s the method of operation that provides a security checkpoint. These types of firewalls are generally installed on routers or switches and monitor networks for malicious incoming traffic or data packets coming from untrusted sources.

These firewalls execute a rather simple task and do it efficiently. Packet-filtering firewalls inspect source and destination IP addresses, ports, and protocols contained in the header information of data packets.

The data is then verified against the rules and allowed to pass if it correlates with the firewall’s access control list. It gets dropped if a data packet isn’t allowed to pass through the firewall.

One of the best things about packet-filtering firewalls is the limited amount of resources it needs to work. Its functionality is simple, easy to manage, and can quickly resolve certain issues of unwanted traffic.

However, this isn’t the safest firewall solution against malware and cyberattacks. That’s mainly because packet-filtering firewalls check the header, not the payload. Because of this, IP spoofing tactics can be used to circumvent the rules.

Circuit-Level Gateways

A circuit-level firewall works differently than your standard packet-filtering model. These firewalls come with a different primary directive to ensure the safety of established connections.

They do this by analyzing Transmission Control Protocol (TCP) connections or sessions.

Similar to packet-filtering firewalls, circuit-level gateways don’t do content filtering or look at payloads. However, they can offer a slightly higher level of protection and help hide data from unauthorized third parties.

Application-Level Gateway or Proxy Firewall

Proxy firewalls are installed between internal and external systems that exchange data packets over the internet.

A proxy firewall is an interesting choice because it can forward client requests while masking the client’s identity and passing off the data as its own.

Imagine you want to access a website. First, you have to submit a request and wait for the other side to process it before you can browse. A proxy firewall intercepts your request and routes it through a proxy server.

The web server receives the request and sees it as coming from the proxy server, not your actual location or device. This is the basic foundation of VPN services. Proxy servers hide a sender’s geolocation, identification, and other information.

In doing so, a proxy firewall can help bypass restrictions and prevent cyberattacks by keeping your identity hidden.

It also has the advantage of limiting contact with unsecured or untrusted networks, which can prevent malware infections. Proxy firewalls are most commonly used for securing web applications and providing browsing anonymity.

But these perks come at an added financial and resource cost.

Stateful Inspection Firewall

Stateful inspection firewalls are some of the best security devices you can use to protect your network from malicious incoming and outgoing traffic.

Unlike other types of firewalls, these track entire connections and prevent unexpected data from entering the network, thanks to the complex traffic filter.

Each connection and data request prompts the firewall to store the connection information in a database known as a state table. Then, it analyzes specific details like the source and destination port, IP addresses, etc.

This is when things get interesting. A stateful inspection method enables firewalls to dynamically create rules that will allow anticipated traffic to pass through the filter.

Essentially, stateful inspection firewalls perform more in-depth checks and inspect both headers and payloads. At the same time, they can work with fewer ports to increase security and handle multiple packets simultaneously.

Make no mistake. Stateful inspection firewalls are resource-hungry and can slow down a network’s performance. And while these types of firewalls are great for blocking protocol vulnerabilities, they can still be taken down by massive, coordinated DDoS attacks.

Despite the shortcomings, stateful firewalls offer a good balance between application proxy requirements and basic packet-filtering needs.

Next Generation Firewalls

The term next-gen is used in IT and cybersecurity to indicate something of superior design and performance. In many ways, that’s what next-generation firewalls are.

These devices can perform multiple functions that other firewalls offer as standalone services. Therefore, you can get packet-filtering and stateful inspections for maximum network and device security.

Deep packet inspection is also available. This function may include additional benefits or security measures like application control, spam filtering, antivirus software, and monitoring of multiple network layers.

But a deep packet inspection firewall is not an affordable solution, at least for personal use. In addition, using a next-generation firewall often requires experienced IT support and a detailed configuration to eliminate incompatibilities with existing network security systems.

For the most part, companies that must maintain HIPAA and PCI compliance are most likely to use a next-generation firewall.

Differences Between Software, Hardware, and Cloud Firewalls

A hardware firewall is a physical device or appliance that operates similarly to traffic routers. They’re used to intercept and filter data packets before connecting requests to the network.

These are also known as perimeter security devices. Hardware firewalls typically excel at stopping malicious traffic before it reaches the network endpoints and causes damage to the system.

But hardware firewalls have one major flaw. Despite the ability to detect malicious traffic, they’re vulnerable to direct interference. Sure, they might be great on paper against hackers that try to breach networks remotely. However, insider attacks can easily bypass or remove them from the network.

That said, there’s no reason you couldn’t use both hardware and software firewalls to have as many security checkpoints as possible. Remember that hardware firewalls are more limited than their software and cloud counterparts and can’t manage too many simultaneous connections.

A software firewall is a different ball game. These programs are installed on devices, not separate hardware components or servers.

One of their biggest advantages is the ability to isolate individual network endpoints to increase security.

The downside of software firewalls is management. Managing multiple software licenses on multiple devices is time-consuming and requires perfect coordination. In addition, some network devices could be incompatible with certain firewalls.

This can lead to instances of using multiple firewalls to cover every device or settling for something that has excellent compatibility yet may lack in security and resource usage.

Cloud firewalls and proxy firewalls are sometimes used as interchangeable terms. The concept of a firewall-as-a-service, or FaaS, is great regarding scalability. It makes adding more capacity for a growing organization easy, and can do an amazing job for perimeter security.

Protect Yourself Against Malicious Traffic

Using a firewall is mandatory these days, whether you’re trying to protect a network, personal computer, workstation, or smartphone.

Your personal information and other sensitive data could be targeted at any moment, and firewall protection can be the first line of defense against attackers. Find the best firewall type for your unique requirements and prevent breaches instead of reacting to them.



Frequently Asked Questions

What is the most popular firewall?

The BitDefender Box is arguably the most popular hardware firewall, while BitDefender Total Security is perhaps the most popular and well-received software firewall suite.

What are the major types of firewalls?

The major types of firewalls are packet-filtering, gateway-level or proxy, stateful inspection, circuit-level, and next-generation firewalls.

Is a VPN a Firewall?

A VPN works based on the proxy firewall principle and can be considered a kind of firewall, as it protects against malicious traffic and unauthorized access requests.

Author: Tibor Moes

Author: Tibor Moes

Founder & Chief Editor at SoftwareLab

Tibor is a Dutch engineer and entrepreneur. He has tested security software since 2014.

Over the years, he has tested most of the best antivirus software for Windows, Mac, Android, and iOS, as well as many VPN providers.

He uses Norton to protect his devices, CyberGhost for his privacy, and Dashlane for his passwords.

This website is hosted on a Digital Ocean server via Cloudways and is built with DIVI on WordPress.

You can find him on LinkedIn or contact him here.

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