In networking, “state” refers to the context or session data of a current network connection. A stateful firewall, therefore, keeps track of the state of each connection passing through it, while a stateless firewall does not.
Although they may sound less restrictive, stateless firewalls are incredibly useful for securing home and business networks. They use ACLs (Access Control Lists) to determine which traffic to allow through and which traffic to block.
Of course, not tracking the state of network connections means that stateless firewalls can’t tell you as much about the traffic on your network as stateful firewalls. The benefits of stateless firewalls come with tradeoffs.
Businesses often balance these trade-offs by using both types in tandem, with stateless firewalls handling bulk traffic filtering at the perimeter and stateful firewalls offering deeper inspection behind them.
By the end of this post, you’ll know when stateless firewalls work really well, and when another solution might work much better.
Five reasons to use a stateless firewall
1. They’re efficient
The biggest advantage of using a stateless firewall is efficiency. Since they only check for individual packets (rather than tracking the state of connections like their bulky stateful counterparts), stateless firewalls are like lean, mean, security machines.
This makes them far more useful when handling high volumes of traffic. For instance, since they don’t have to keep up with the specific details of every connection passing through, stateless firewalls won’t chew up as much memory and processing power.
If you’re running a large-scale website that receives tons of traffic, for example, you won’t want your firewall to slow things down. With a stateless firewall, you can set up strong network security protections without jeopardizing a website’s performance.
SEE: Avoid these mistakes when configuring network security.
2. Stateless firewalls are simple to set up and maintain
Setting up a stateless firewall is a breeze compared to stateful firewalls.
Stateful firewalls dynamically maintain state tables to track ongoing connections, ensuring traffic flows are legitimate by monitoring session information.
In contrast, stateless firewalls rely on a fixed set of filtering rules, such as allowing or blocking packets based on IP addresses, ports, or protocols. This makes stateless firewalls simpler to configure and less resource-intensive, though it also makes them less adaptable to dynamic or context-dependent traffic than stateful firewalls.
3. Stateless excels on the network perimeter
Stateless firewalls are often used as a first line of defense in network security due to their simplicity and effectiveness at blocking unwanted traffic.
They are particularly useful in scenarios where only basic access control is needed, such as filtering traffic between trusted and untrusted networks. This protects specific services from common attacks like port scans, denial-of-service (DoS) attacks, or VoIP fraud.
While they may not offer the deep inspection or session awareness of stateful firewalls, they can serve as an effective initial barrier, reducing the load on more advanced systems by blocking simple, high-volume threats before they reach more sensitive parts of the network.
4. They’re inherently less vulnerable
Stateless firewalls don’t keep track of past traffic or active connections, which makes them less prone to certain types of attacks that target the firewall’s memory or stored data.
Instead, stateless firewalls simply compare incoming packets to their pre-defined “allow” and “deny” rules, ensuring that traffic is only allowed into the network if it meets specific criteria. This straightforward approach ensures that only authorized traffic enters the network.
Since they don’t need to manage the details of each connection, stateless firewalls avoid some of the vulnerabilities that can arise when a firewall tries to remember everything, like becoming overloaded during different types of DDoS attacks, where attackers flood the system with too many requests.
Stateful firewalls offer deeper inspection and more thorough security, but that introduces additional complexity, which can be exploited by attackers. Stateless firewalls, with their simpler design, avoid this risk altogether.
5. Stateless firewalls are cost-effective and affordable
Because they don’t require the advanced features of stateful firewalls, such as session tracking or deep packet inspection, their hardware and maintenance costs are significantly lower. This makes them an accessible choice for organizations with limited IT budgets or smaller networks.
Stateful firewalls are more expensive due to their advanced features, such as integrated intrusion detection and prevention systems. These firewalls also require more processing power, memory, and specialized hardware to manage real-time traffic analysis and maintain security.
Key downsides of a stateless firewall
While stateless firewalls have their advantages, they also come with some downsides.
1. Minimal packet inspection capabilities
Since it doesn’t keep track of connections, a stateless firewall won’t maintain a table of all the previous connections that have gone through the firewall. This makes it faster and easier to handle high volumes of traffic, but it comes with minimal packet inspection capabilities.
For example, stateless firewalls can only inspect individual packets based on headers and protocols, meaning they cannot look at the contents of the packets themselves. This makes them less effective at detecting and preventing more sophisticated attacks that can bypass simple packet inspection, such as ones that use encrypted traffic.
Moreover, due to the lack of connection tracking, a stateless firewall cannot always distinguish between legitimate and malicious traffic. This can result in unnecessary blockages of legitimate traffic, which can disrupt business operations. It also makes it more difficult to modify the firewall, as stateless firewalls cannot recognize connection states — so they can’t allow and deny traffic dynamically based on them. Learn more about how stateful inspection works.
2. Harder to scale
One of the biggest downsides to stateless firewalls is that they can be an absolute nightmare to scale in certain scenarios.
The problem lies in the fact that a stateless firewall only examines individual packets to determine whether to allow or deny them. This means that, as the number of connections to your network increases, so does the number of rules in your firewall. Therefore, when your network has a high volume of traffic, it can be extremely difficult to manage and maintain.
Unfortunately, with stateless firewalls, you need to create manual rules for each kind of packet that travels through the network. This can lead to a situation where there are simply too many rules to manage — which can lead to network performance issues, security flaws, and massive administrative overheads. Learn more about how to create a firewall policy that works for your network.
3. Initial configuration to work properly
Although stateless firewalls are a breeze to set up compared to stateful firewalls, the process isn’t exactly the easiest.
Stateless firewalls can require a fair bit of initial configuration to work properly. For instance, since they don’t maintain connection states, they must rely on other factors—such as IP addresses and port numbers—to determine whether or not incoming packets are allowed into the network.
This means that, in addition to the aforementioned filtering rules, some additional settings require careful configuration to ensure that legitimate traffic is allowed through while malicious traffic is blocked. Learn more about how to set up a firewall properly.
