Stateful vs. Stateless Firewall Differences

Protecting business networks has never come with higher stakes. The average cost for stolen digital files containing sensitive proprietary information has risen to $148 each. When you consider how many files cybercriminals may get away with in a given attack, the average price tag of $3.86 million per data breach begins to make sense.

Given that, it’s important for managed services providers (MSPs) to understand every tool at their disposal when protecting customers against the full range of digital threats. While each client will have different needs based on the nature of their business, the configuration of their digital environment, and the scope of their work with your team, it’s imperative that they have every possible defense against increasingly malicious bad actors.

Computer firewalls are an indispensable piece of network protection. By protecting networks against persistent threats, computer firewalls make it possible to weed out the vast majority of attacks levied in digital environments. Although firewalls are not a complete solution to every cybersecurity need, every business network should have one.

However, not all firewalls are the same. They can often be broken down into stateful firewall vs. stateless firewall options. Each has its strengths and weaknesses, but both can play an important role in overall network protection.

What does stateful firewall mean?

A stateful firewall is a firewall that monitors the full state of active network connections. This means that stateful firewalls are constantly analyzing the complete context of traffic and data packets, seeking entry to a network rather than discrete traffic and data packets in isolation.

Once a certain kind of traffic has been approved by a stateful firewall, it is added to a state table and can travel more freely into the protected network. Traffic and data packets that don’t successfully complete the required handshake will be blocked. By taking multiple factors into consideration before adding a type of connection to an approved list, such as TCP stages, stateful firewalls are able to observe traffic streams in their entirety.

However, this method of protection does come with a few vulnerabilities. For example, stateful firewalls can fall prey to DDoS attacks due to the intense compute resources and unique software-network relationship necessary to verify connections.

What is the main difference between stateful and stateless packet filtering methods?

Stateless firewalls are designed to protect networks based on static information such as source and destination. Whereas stateful firewalls filter packets based on the full context of a given network connection, stateless firewalls filter packets based on the individual packets themselves.

To do so, stateless firewalls use packet filtering rules that specify certain match conditions. If match conditions are met, stateless firewall filters will then use a set of preapproved actions to guide packets into the network. If match conditions are not met, unidentified or malicious packets will be blocked.

Because stateless firewalls do not take as much into account as stateful firewalls, they’re generally considered to be less rigorous. For example, stateless firewalls can’t consider the overall pattern of incoming packets, which could be useful when it comes to blocking larger attacks happening beyond the individual packet level.

Is Windows Firewall stateful or stateless?

For many private or SMB users, working with the firewalls provided by Microsoft is their primary interaction with computer firewall technology. For several current versions of Windows, Windows Firewall (WF) is the go-to option. WF is a stateful firewall that automatically monitors all connections to PCs unless configured to do otherwise.

For users relying on WF, the platform will log the information of outgoing packets, such as their intended destination. When information tries to get back into a network, it will match the originating address of incoming packets with the record of destinations of previously outgoing packets. This helps to ensure that only data coming from expected locations are permitted entry to the network.


Check out our blog for other useful information regarding firewalls and how to best protect your infrastructure or users. 

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