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What is a firewall?

Read our guide to learn what firewalls are, the different types, best practices and how they can protect your network from cyber threats.


Firewalls act as a digital barrier, separating your internal network from the threat of hackers. And without one, your reputation and your organization are at risk.

We’ll be looking at everything to do with firewalls and how they can help to keep your data safe, without getting too technical. Here’s what we’ll be covering: 

  • What are firewalls and what is their purpose?
  • A brief history of firewalls
  • How do firewalls work?
  • Different types of firewalls
  • Benefits of firewall protection
  • Firewall features and functionality
  • Firewall considerations
  • Challenges, risks and limitations of using a firewall
  • Firewall security tips

What are firewalls and what is their purpose?

A firewall is one of the most important tools in your cybersecurity arsenal. It’s the gatekeeper guarding your device or network against the threat of malicious actors.

It monitors and controls incoming and outgoing traffic, but, most importantly, it prevents unauthorized access from filtering through.

The purpose of a firewall is simple. To protect your data from falling into the wrong hands. Firewalls are also used internally to segment network traffic and restrict access to sensitive resources.

They use predetermined security rules to determine whether the entry should be blocked or allowed. These rules can be based on various factors, such as the source or destination IP address, port number, protocol, and more.

A brief history of firewalls

Firewalls date back to the late 1980s, when the internet was in its infancy. In those days, computers were primarily used by academic institutions and government organizations. Once the internet expanded and became commercialized, the need for network security increased alongside it.

The first firewall was developed in 1987 by the Digital Equipment Corporation (DEC), but back then it was called a packet filter firewall. Its mission? Examine each packet of data passing through the network and determine entry based on predefined rules. It was simple but effective.

As the Internet grew more popular during the 1990s, network threats grew more sophisticated, and the need for more advanced firewalls became apparent.

This led to a whole new generation of firewalls: stateful inspection firewalls, application layer firewalls, circuit-level gateways, and more.

Firewalls continue to evolve with the ever-changing landscape of digital threats. They’re an essential component of any cybersecurity strategy and provide hardware, software, as well as cloud-based solutions.

How do firewalls work?

Overall, firewalls examine network traffic and block potential malware, viruses, and hacking attempts.

The way they protect against threats depends on the type of firewall in question, but most follow a few basic principles.

  1. Packet inspection: the firewall carefully examines each packet of data passing through. It analyzes aspects like its origin, destination, port, and protocol.
  2. Stateful inspection: some firewalls also examine the context and state of connections between packets of data. This helps it make more intelligent decisions about entry rights.
  3. Access control: if the data packet doesn’t align with security rules and fails to pass the packet or stateful inspection, access is denied. Entry is blocked and dropped.
  4. Logging and reporting: firewalls log information about incoming and blocked traffic, which can then be used to analyze network traffic and identify potential security threats. 

Different types of firewalls

There are several types of firewall, each with its own set of unique characteristics. Here are some common examples of firewalls. 

Network firewall

This is your run-of-the-mill firewall. The security guard standing at the perimeter of your network also commonly known as an edge device, controlling who can come in and out. It typically uses packet filtering or stateful inspection to filter traffic.  

Host-based firewall

Think of a host-based firewall as the door lock of an individual room. It protects specific devices or hosts from unauthorized access. It filters traffic based on rules and policies set by an administrator and can be more granular than network firewalls. 

Web application firewall 

Your web application firewall is a specialized type of security guard that monitors and controls traffic to and from applications or services. It can target web or email servers and block attacks specific to the application they are protecting. 

Next-generation firewall 

Next-generation firewalls are where things start to get fancy. It’s like having a high-tech security team guarding your network. And they’re equipped with all the latest features, such as intrusion prevention systems, deep packet inspection, application awareness, and advanced threat intelligence.

Virtual firewall

These firewalls act as virtual security checkpoints. They’re digital barriers that run in virtualized environments and provide security for virtualized infrastructure. They perform the same function as a hardware firewall, just in another format. 

Cloud firewall

Cloud firewalls are security guards that protect data and applications hosted in cloud environments. You can manage cloud firewalls through web-based consoles and easily scale them to accommodate changing traffic volumes.

Personal firewall

Last but not least, a personal firewall is like having a personal bodyguard for your device. You can install this on your individual computer and use it to avoid unauthorized access or malware from infecting the system. 

Benefits of firewall protection

The advantages of firewall protection include:

  1. Network protection – firewalls create a crucial layer of defense against malicious threats, such as viruses, hackers, or malware.
  2. Traffic control – organizations can control and manage incoming and outgoing network traffic, preventing network congestion and optimizing performance.
  3. Application-level security – this provides precise control, advanced threat detection and proactive defense against application-layer attacks.
  4. Regulatory compliance – firewalls maintain the integrity of your organization and demonstrate adherence to compliance standards by ensuring confidential information remains protected.
  5. Remote access security – network firewall security can ensure remote workers or contractors don’t compromise the integrity of your system.
  6. Cost-effective – data breaches are costly, but installing firewalls is an effective way to enhance network security. 

Firewall features and functionality

Ideally, your firewall should leave no stone unturned and cover all bases. Here are some of the most common features to look out for. 

  1. Packet filtering – filters network traffic based on predefined rules to allow or deny packets based on source/destination IP, port, or protocol.
  2. Stateful inspection – examines the context of network connections to track and validate the state of each packet.
  3. Application awareness – monitors and controls application-level traffic with granular control to protect against specific threats.
  4. Intrusion prevention system – detects and blocks malicious threats in real-time to provide proactive defense against network-based attacks.
  5. Virtual private network support – enables secure remote access and communication by encrypting traffic between networks or users to ensure confidentiality and privacy.
  6. Logging and reporting – logs firewall events and generates comprehensive reports for auditing, analysis, and compliance purposes.
  7. Centralized management – provides a unified interface to manage multiple firewalls, simplifying administration and ensuring consistent security policies.
  8. Threat intelligence integration – integrates with external threat intelligence sources to enhance threat detection and response capabilities, keeping your firewall updated with the latest threat information.

Firewall considerations

Want to install the best firewall for your business? Here are some key things to consider. 

Security requirements

Firstly, you’ll need to understand your organization’s specific security requirements. How sensitive is your data? What level of regulatory compliance do you need to meet? What’s the potential impact of a security breach?  

Firewall Type

Then you’ll need to consider the size and architecture of your network. Choose a firewall with features that fit the requirements of your security network.  


Ensure the firewall solution can scale as your network grows. Consider the number of expected users, devices, and network traffic volume. Your firewall should be capable of handling current and future demands. 

Ease of management

There’s no point in installing a firewall you can’t manage efficiently. Centralized management consoles or interfaces offer intuitive configuration, monitoring, and reporting features that greatly simplify administration and troubleshooting tasks.

Integration with existing infrastructure

Find a firewall that will integrate smoothly with your existing network infrastructure. Compatibility and interoperability are crucial for a cohesive and effective security ecosystem.

Advanced threat protection

Look for advanced threat protection features, such as intrusion prevention, anti-malware, sandboxing, or threat intelligence integration. These additional layers of security can enhance the firewall’s effectiveness against emerging and sophisticated threats.

Virtual Private Network (VPN) support

Need to account for remote access? Verify that the firewall supports secure VPN connectivity.

Consider the supported VPN protocols, encryption algorithms, authentication methods, and the scalability of VPN connections to accommodate remote users or branch offices.

High availability and redundancy

Consider implementing redundant firewall solutions or high availability configurations to ensure continuous network protection in case of hardware failures or maintenance. Redundancy can help minimize downtime and maintain business continuity.

Regular updates and support

Ensure that the firewall vendor provides regular firmware updates,

, and ongoing technical support. Promptly applying updates ensures the firewall remains effective against the latest threats. 


Finally, consider your budget. Firewalls entail upfront and ongoing costs, including hardware, licensing, maintenance, and support fees. Balance the potential cost with the required security features to find the perfect fit. 

Challenges, risks and limitations of using a firewall

Although there are many benefits of firewall protection, there are also some risks that you should be aware of.

  1. False sense of security: firewalls alone don’t guarantee complete protection and they should be part of a comprehensive security strategy.
  2. Misconfiguration: improper firewall configuration can create vulnerabilities for attackers to exploit.
  3. Complex management: firewalls require expertise and resources for effective management, posing challenges for small businesses.
  4. Limitations of packet filtering: traditional firewalls struggle to detect advanced threats hidden in application-level traffic.
  5. Limited visibility: firewalls offer limited real-time visibility into network traffic, hindering incident response.
  6. Overhead and performance impact: advanced firewall features can impact network performance and introduce overhead.
  7. Encrypted traffic: firewalls face difficulties in identifying and blocking threats within encrypted traffic.  

Firewall security tips

To ensure maximum firewall security, bolster its protective features with the following tips: 

Always keep your firewall on

Turning off your firewall to access a specific network or device can leave your entire system vulnerable. If you need to do so, update your firewall rules and add the desired device to your allow list instead. 

Update your OS or firewall software

Always keep your OS or firewall software up to date. Outdated software or operating systems can leave your device vulnerable to exploits and security breaches. 

Use a VPN alongside a firewall

A VPN adds an extra layer of internet security to your firewall by protecting all your device’s traffic in a secure, encrypted tunnel. Ensure your firewall and VPNs do not counteract each other. 

Don’t allow unknown requests

Always deny suspicious or unknown requests that aim to bypass your firewall security. Later, you can investigate the blocked attempt and update your firewall’s rules if necessary.

Install extra security software

While firewalls do a great job of protecting your device from malicious traffic, they do not protect you against malicious programs you might unknowingly install.

For more comprehensive security against malware and other threats, install a trusted malware scanner tool.

Final thoughts

Overall, your firewall should excel at keeping unauthorized access from filtering through. However, the most expensive and fancy firewall may not always be the best choice for your organization.

There are many types of firewall, each with its set of purposes and benefits. Finding the right one for your needs can be challenging, to say the least. Although it is one of the most important tools in your cybersecurity arsenal, by no means should it be the only one.

Don’t be lulled into a false sense of security. The most sophisticated hackers can break through your firewall, especially if it’s guarding your system in the wrong places. Want to put it to the test? Invite us to break in. 

CovertSwarms’ team of experienced ethical hackers will help you create an impenetrable security strategy.

And we won’t just challenge your capabilities, we’ll attack them.

Once we find a way in, we’ll help you develop a response plan and teach you how to patch up vulnerabilities.

Want to know more? Contact a member of the swarm today