Choosing between Stateful vs Stateless Firewalls

Image showing a shield in front of a network.
Which firewall will you choose in the battle between stateful vs stateless firewalls?
Source: Gerd Altmann

Organizational security is getting more sophisticated by the day, yet cybercriminals still manage to find a way to get into your network. Ever wondered why? Well, a study by Stanford University shows that 88% of successful attacks occur due to human errors. Unfortunately, you can’t eliminate the role of human errors in cyberattacks. But you can lower the damage through stringent organizational policies and advanced security tools like firewalls.

But did you know that firewalls come in two kinds? So you need to choose between stateful vs stateless firewalls. And you can’t choose the right option for your business if you don’t know the difference between the two.

In this article, I’ll discuss each of these firewalls and their pros and cons. I’ll then review the top 5 factors for you to consider before choosing one. Finally, I’ll explain which firewall is right for your business. I’m sure you’re eager to learn more, so let’s begin!

What Is a Stateful Firewall?

A stateful firewall thoroughly examines every incoming and outgoing data packet. Specifically, it inspects these data packets’ contents, headers, source and destination, and more. It also saves their states and compares the examined values against the state table’s established baseline values.

Through this process, the firewall can instantly report any deviation. Because stateful firewalls store the states of each data packet, they can easily track behavior changes as they occur. One good example of a stateful firewall is Windows Defender. Here are some more functions of this type of firewall:

  • Mitigates the impact of many human errors
  • Detects unauthorized attempts to access a sensitive resource and thwarts them 
  • Identifies intentional or accidental forged messaging
  • Checks for illicit data and prevents it from entering your network

Now that you know what a stateful firewall is, let’s look at some of its pros and cons.

Pros and Cons of Using a Stateful Firewall

Put simply, a stateful firewall examines the contents of data packets thoroughly to detect possible attacks. And that’s great for your cybersecurity. On the flip side, this comprehensive checking can potentially lower your network’s speed. Check out some more detailed pros and cons of using a stateful firewall.

Logs every event for future referenceRequires regular patch management
Uses past behavior for future decisionsDoesn’t prevent man-in-the-middle (MITM) attacks
Facilitates smooth communications even with just a few open portsRequires high levels of memory and CPU
Retains the key aspects of network connections like the stateIsn’t ideal for most modern applications that tend to use more than one port or change ports often
Pros and cons of using a stateful firewall.

Up next, we have stateless firewalls!

What Is a Stateless Firewall?

While a stateful firewall examines every aspect of a data packet, a stateless firewall only examines the source, destination, and other aspects in a data packet’s header. The stateless firewall will raise an alarm if any of these header parameters are beyond the accepted threshold values. A good example of a stateless firewall is a proxy firewall. Here are some more functions for you to consider:

  • Mitigates human errors during file transfers
  • Prevents any transfers from and to blocked sites
  • Takes up fewer resources
  • Is well-suited for internal networks

As was the case with stateful firewalls, let’s now take a look at the pros and cons associated with using a stateless firewall.

Pros and Cons of Using a Stateless Firewall

In all, stateless firewalls are best suited for small and internal networks that don’t have a lot of traffic. But these firewalls may require extensive configurations, so keep this in mind. Here are some more pros and cons of using a stateless firewall.

Handles heavy traffic wellIs less secure when compared to stateful firewalls
Quick and delivers fast performanceMay need additional configurations
More affordableDoesn’t track the connection’s status, so you can’t infer any intelligent behavior patterns
Consumes fewer resourcesWorks well in limited scenarios only, such as VLANs in a network
Pros and cons of using a stateless firewall.

Now that you have a good idea of the differences between stateful vs stateless firewalls, what’s next? Well, I think it’s important to highlight some important factors before choosing a particular firewall. Let’s go over those now.

Top 5 Factors to Consider When Choosing a Firewall

But how can you properly choose between stateful vs stateless firewalls? You need to keep the end goal in mind — to have a robust cybersecurity system for your business. So here are 5 considerations that can help you achieve this goal and make the choice.

1. Deployment Flexibility

In today’s dynamic business environment, you should choose a firewall that supports flexible deployment. Ideally, you’d want a firewall to deploy as software on your hardware. This can be as a hardware appliance by itself or even in an existing VMware environment.

The advantage of having this flexibility is that you can choose your software and hardware based on your business’s needs. Unfortunately, this feature isn’t readily available in all firewalls, except a few like GFI Software’s KerioControl.

2. Detailed Statistics

Though most firewalls focus on blocking malicious packets, an equally important feature is identifying individual users’ usage statistics. As a business owner, knowing these statistics can help you formulate granular policies, boost employee productivity, and more. Luckily, this feature is very common in many stateful and stateless firewalls!

Image showing a magnifying glass, bar charts, pie diagrams, and some graphs.
Leverage analytics to boost overall productivity!
Source: ColiN00B on Pixabay

3. Next-Generation Firewall (NGFW) Capabilities

As networks become more complex, organizations should have a unified firewall that monitors networks, data, apps, etc. A next-generation firewall (NGFW) is the solution. This firewall’s capabilities include the functionality of a router, VPN services, antivirus, app filtering, and more.

Though NGFWs are becoming more common, choosing the right one requires considerable research. You should start with a list of features you want and work your way through the available options on the market.

4. Web and Application Filtering

Given the ever-growing number of apps and websites, you should have a firewall that can restrict access to blocklisted or unknown apps and websites. You can also use this feature to prevent employees from accessing bandwidth-hogging apps. Unfortunately, finding a firewall with this feature isn’t easy. Some exceptions, however, do exist on the market.

5. Virtual Private Network (VPN) Service

A firewall that doubles as a virtual private network (VPN) can help remote users safely connect to your network. You can also easily connect branch offices with your head office. Overall, this feature can come in handy for SMBs and enterprises alike. 

Alright, those are 5 factors for you to consider before you venture out in search of a firewall. But wait, don’t leave just yet! We have to answer a very important question for SMBs and enterprises alike. Should you choose a stateful or stateless firewall? Let’s find out.

Should You Choose a Stateful or Stateless Firewall?

Choosing between a stateful and a stateless firewall largely depends on the size and nature of your business. Let’s first look at the needs of a smaller business.

Stateful vs Stateless Firewalls for SMBs

A stateless firewall can be a better option for small businesses as it’s cheap, affordable, and provides the basic protection your business needs. More importantly, since smaller businesses have less traffic load than large businesses, the chances of threats occurring are very low. Also, many human errors in small businesses are file transfers to blocked addresses, misconfigurations, etc. A stateless firewall can handle those easily.

Image showing a small store.
A stateless firewall is a good choice for smaller businesses!
Source: Satheeshsankaran on Pixabay

Stateful vs Stateless Firewalls for Enterprises

A stateful firewall is the best choice for large enterprises. This is because they grapple with ever-growing cyber threats like malware. As mentioned earlier, stateful firewalls inspect all aspects of any incoming data packets. Malware can sometimes disguise itself as a data packet’s contents, so having a stateful firewall in place is a good solution. Also, enterprises will have the resources to support and maintain a stateful firewall in the long run.

Time for a quick recap!

The Bottom Line

To conclude, you should look at several factors when it comes to stateful vs stateless firewalls. For SMBs, stateless firewalls are the way to go since these firewalls are affordable, quick, and don’t require many resources. Remember that these firewalls are less secure, though. If you need robust security, you should go for a stateful firewall. But since stateful firewalls require a lot of resources and are costly overall, only larger businesses should invest in them. Either way, you’ll be sure to mitigate the risk of human error in your business.

In a sense, you need to choose between budget and security. Think about your business’s needs and requirements. What does it need from a firewall? The answer to this question will save you time and trouble. We hope this article gave you some insights. As always, feel free to refer back to it if you need a quick refresher.

Do you have more questions about stateful vs stateless firewalls? Check out the FAQ and Resources sections below!


Since I rely heavily on the TCP protocol, which firewall should I choose?

When it comes to stateful vs stateless firewalls, a stateful firewall is a good choice for TCP connections. To elaborate, TCP tracks its connections through source and destination addresses, port numbers, and more. This is why stateful firewalls are a good choice, as they’re a natural extension of storing data packet states.

What are some examples of stateless firewalls?

User Datagram Protocol (UDP) is a stateless connection that, in turn, uses a stateless firewall. Likewise, FTP connections that you use to transfer files work well with stateless firewalls. IP and HTTP are stateless as well. 

Are the layers in the OSI model considered stateful firewalls?

To some extent, yes. Some of these layers can be stateful firewalls. For instance, Layer 3 contains a stateful firewall as it tracks sources and destination addresses. Similarly, Layer 4 can be stateful or stateless, depending on whether you use TCP or UDP, respectively.

Can stateful firewalls prevent flood attacks?

No, stateful firewalls can’t prevent flood attacks like Distributed Denial-of-Service (DDoS) attacks. These firewalls can’t track TCP flood attacks as they don’t have the required in-depth visibility. Moreover, stateful firewalls can’t communicate with cloud-based resources to mitigate the impact of these attacks. 

Is the Windows Defender firewall stateful?

Yes, the Windows Defender firewall is stateful. With this firewall, you can create rules to determine which kinds of traffic can pass through your network. It also supports IPSec. This means that you can mandate authentication for any device that wants to communicate with your device.


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