A stateful firewall keeps track of the state of network connections. A stateless firewall does not. Although the difference between a stateful vs stateless firewall is relatively simple, picking one may not be as straightforward.
The state of a network connection refers to its status, whether a connection is being established, actively transferring data, or closing.
Stateful firewalls keep track of this context, monitoring the entire flow of communication — where packets are coming from, where they are going, and what type of traffic is being relayed.
Stateless firewalls ignore this context — they treat each packet as independent, and have no knowledge of prior packets.
These fundamental differences make stateful firewalls appropriate in some situations and stateless firewalls better in others.
When use a stateful vs stateless firewall
Stateful firewalls are necessary in dynamic, complex environments where tracking the state of connections is important for security. They offer deeper inspection capabilities, which makes them well-suited for networks with diverse traffic flows or where detecting malicious activity within ongoing sessions is critical.
Stateless firewalls are ideal for static networks with predictable traffic patterns, where packets can be allowed or blocked based on fixed rules without needing session tracking. These firewalls provide a low-maintenance solution for scenarios that don’t require deep inspection of connection states, such as enforcing basic port restrictions or as a first layer of defense in a high-speed environment.
There are several different types of firewalls, which may be stateless or stateful. A packet-filtering firewall is typically stateless, a Web Application Firewall (WAF) is typically stateful, a Firewall as a Service (FWAAS) could be either stateful or stateless.
SEE: Five reasons a stateful firewall is a must-have for any business.
Tradeoffs between a stateful vs stateless firewall
A stateful firewall will always be able to tell you more than a stateless one, but it comes at a cost. Is it better to opt for the speed and performance of a stateless firewall?
As you set up firewalls and secure different parts of your network, here are the main trade-offs to consider when looking at stateful vs stateless firewalls.
1. Stateful firewalls consume more resources
Because stateful firewalls inspect packets and track the state of network connections, they have a lot slower performance than stateless firewalls. In the wrong place or with the wrong task, a stateful firewall can really slow down your network.
Meanwhile, stateless firewalls are a much faster alternative because they operate by examining the source and destination addresses of individual packets. This means they ignore the connection states and can therefore resolve incoming packets much faster.
Altogether, stateless firewalls are far more suitable in high-traffic, low-risk situations. With their superior speed, they can assess packets quickly without putting a strain on network resources. When the security level requires a bit more intensive work, stateful firewalls are usually worth the performance hit.
2. Stateful firewalls are less likely to trigger false positive alarms
Stateless firewalls can have a tendency to put your network in a constant “fight or flight” type of condition. This isn’t as common with stateful firewalls, and that’s simply due to the way they track the state of connections.
Stateful firewalls can and will recognize established connections, so they’re more sensitive about blocking traffic rather than tossing up a red flag whenever anything that might be suspicious comes their way (as stateless firewalls tend to do).
Overall, stateless firewalls are way more likely to generate false positives and block legitimate traffic because they lack context.
In practical terms, this means that stateful firewalls tend to offer more nuanced control over your traffic — which is useful for networks that are more complex or transmit more sensitive data.
Financial institutions and healthcare providers, for example, may find this particularly advantageous because they generally have stringent security requirements.
3. Stateful firewalls can apply more flexible rules
Let’s say you’re an IT administrator who’s in charge of securing your organization’s network. If you ensure firewall rules follow best practices, a stateful firewall will enable you to enforce those rules with a bit more precision. In other words, you’ll have more reliable, consistent protection.
However, if your traffic is more varied — and therefore more unpredictable — a stateful firewall can be a better choice because it lets you apply rules at the packet level. This can be especially helpful when you need to let certain traffic pass through that might not fit into a predefined set of rules so easily.
For example, if a software development company frequently collaborates with third-party vendors, it’s very likely that the traffic coming in from these vendors is highly varied. By using a stateful firewall that can apply more flexible rules, they are able to manage varying traffic patterns and maintain network security.
4. Stateless firewalls don’t track connection states
This design choice reduces the complexity of managing session data, which translates to lower overhead for the firewall. As a result, stateless firewalls are much lighter in terms of resource consumption — they require less processing power, memory, and storage compared to stateful firewalls. This makes them highly efficient for environments where speed and scalability are critical, especially in handling large volumes of traffic.
One instance where this can be especially useful is in a cloud computing environment with virtual servers and workloads that frequently increase and decrease. In this environment, a stateless firewall could theoretically be deployed to make sure the traffic going in and out of the cloud-based resources follows a predetermined set of rules.
The lack of state-tracking becomes a trade-off when considering dynamic or complex traffic scenarios. The simplicity of stateless firewalls comes at the cost of not being able to detect or block threats that rely on context, such as session hijacking or more sophisticated attack vectors. Ultimately, the trade-off is between efficiency and security.
5. Stateless firewalls offer less control
Although stateless firewalls can be more agile and light-footed, they offer far less precision.
Without storing the state of a network connection, stateless firewalls treat each packet that passes through them as individual entities — with no consideration for the packets that came before or after them.
As a result, stateless firewalls are pretty limited in their ability to differentiate between permitted and unpermitted traffic. With a stateful firewall, however, when an initial request to access a secure website is allowed to pass through, subsequent packets are then identified as part of the same connection.
6. Stateful firewalls have a cost
Stateful firewalls are generally considered to be more advanced, functional, and efficacious than stateless firewalls. At the end of the day, they’re better at tracking the state of different network connections and then making decisions on that state.
That said, with that thoroughness comes a heftier price tag. Stateful firewalls also require more powerful hardware to operate at full capacity and they are more complex to deploy.
You don’t have to choose between a stateful vs stateless firewall
Businesses often deploy both stateless and stateful firewalls as complementary layers in their network security architecture. It’s not one or the other.
Stateless firewalls are typically placed at the network perimeter to handle high-speed traffic filtering, blocking unwanted packets based on simple rules. Behind them, stateful firewalls provide deeper inspection and context-aware security by monitoring connection states, ensuring legitimate sessions are protected.
This layered approach balances performance and security, allowing businesses to efficiently manage traffic while addressing more sophisticated threats within the network. Learn more about where firewalls should sit on your network and explore the latest network security tools you can use to keep your business data secure.
