What Is a Stateful-Inspection Firewall? Are They Right for You?

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A stateful-inspection firewall is a type of firewall that tracks and monitors the state of active network connections. These firewalls also analyze incoming traffic headed to the network, checking for potential traffic or data risks. Stateful-inspection firewalls are situated at Layers 3 and 4 of the OSI model.

How Stateful Inspection Works

Stateful-inspection firewalls—also called dynamic packet-filtering firewalls—collect data about every connection trying to get through to a network. From these data points, a collection of profiles, previously established by the network administrator, deem connections safe or unsafe.

When someone tries to make a connection to the firewalled network, the firewall checks the connection request data against the list of profiles and safety qualities the firewall collects. If it determines the data’s attributes are safe, the firewall will allow the connection; otherwise, it will deny and discard any data packets missing the required parameters. In the event there is no matching entry for new data packets, the packet will undergo specific policy checks and will be allowed if it meets the requirements.

Top 3 Advantages of Stateful-Inspection Firewalls

Stateful-inspection firewalls provide a more dynamic and dependable layer of security over their stateless cousins. Among the strongest advantages of stateful firewalls are their flexibility and suitability to both TCP and UDP standards, their higher level of security, and their contextualization of data states.

1. They’re Well-Suited to Both TCP and UDP

Stateful-inspection firewalls are the direct opposite of stateless-inspection firewalls, also referred to as static packet-filtering firewalls. Unlike stateless firewalls, which simply read packet headers before allowing or blocking the packet, stateful firewalls monitor ongoing activity across the network. This makes them well-suited to both TCP and UDP—and any packet-switching IP.

2. They Provide a Greater Degree of Security

Compared to other types of firewalls, stateful inspection offers much better security because it analyzes traffic at several layers in the network stack. It also provides more granular control over traffic filtering procedures for IT professionals than stateless inspection.

3. They Take State and Context Into Account

Stateful inspection tracks the full state and context of data, which is more complex than what occurs in a stateless infrastructure. When users access a web server, the firewall identifies the response and can analyze all the data packets and details such as their source, destination, and content. If packets contain malicious code not alluded to in their header, a stateful-inspection firewall will still be able to discard them to prevent a cyber incident.

Top 4 Disadvantages of Stateful-Inspection Firewalls

Despite their advantages, stateful-inspection firewalls still come with some disadvantages worth knowing. For one, their configuration can be complex—a factor true of most firewalls, but especially advanced next-generation firewalls (NGFWs). In addition, they cannot prevent application-layer attacks, they lack user authentication, and they cannot provide web application security.

1. Complex Configuration

Configuring a stateful-inspection firewall is challenging because they require more processing and memory resources to maintain session data. Since they offer better security, it can take more time for IT administrators to configure the firewall based on company needs. 

On the other hand, some network administrators may find this complexity beneficial, because these firewalls allow them to set specific, granular parameters required to defend against advanced cyberattacks.

2. Cannot Prevent Application-Layer Attacks

Stateful-inspection firewalls are also more susceptible to certain kinds of cyber attacks, such as layered attacks or distributed denial of service attacks (DDoS). DDoS threats are becoming increasingly sophisticated—one attack was capable of taking down New Zealand’s stock exchange in 2020.

3. Lack User Authentication of Connections

User authentication is a critical component of maintaining a strong cybersecurity posture. Unfortunately, stateful-inspection firewalls do not carry user authentication capabilities. They can check the source of a packet, but not verify its identity.

4. Does Not Provide Web Application Security

Another drawback of stateful-inspection firewalls is they do not account for web applications and the dynamic port numbers many use for auxiliary connections. Nearly every business uses web applications to operate and threat actors might use these as attack vectors. Companies using stateful inspection may also need to leverage a web application firewall or application-level gateway, which offers a handful of benefits such as protection, ease of use, and continuous monitoring.

3 Common Features of Stateful-Inspection Firewalls

Although stateful inspection is a great security measure to implement, it’s critical for companies and their IT departments to run configuration checks consistently. IT professionals can also test the effectiveness of their company’s firewalls—including a stateful-inspection firewall—by running a firewall penetration test.

In addition to some of the benefits and drawbacks listed above, stateful-inspection firewalls typically share some common features, such as:

  • Encryption 
  • Tunnels
  • Robust attack prevention

Stateful-inspection firewalls can prevent some—but not all—DDoS attacks compared to basic packet filtering, helping companies avoid extended downtime. They also have more robust logging capabilities to store essential aspects of network connections.

3 Best Stateful-Inspection Firewall Vendors

There are several networking providers that sell products and services to help companies bolster their cybersecurity strategies, including firewall management. Here are three of the best:

Cisco: Best overall

Cisco Secure Firewall can provide top-notch security at an affordable rate, whatever the size of your organization. Cisco’s firewalls implement a Firewall Stateful Inspection of ICMP (Internet Control Management Protocol) to help network administrators debug network issues and control safe/benign data. Cisco also offers various other solutions, including its software-defined wide area network (WAN) and Umbrella, a cloud-based firewall.

Key features

  • Real-time threat intelligence through Cisco Talos
  • Scalable integration with SecureX platform
  • Internal network segmentation provides enhanced cloud security


  • Comparatively simple deployment and management
  • Extremely stable and regularly updated
  • Detailed reporting


  • Device management interface can be slow and complicated
  • Integrations can become expensive


Cisco doesn’t list pricing on their website, but you can fill out a form to book a demo, start a free trial, or get a quote from a sales representative.

Palo Alto Networks: Best for enterprises

Palo Alto Networks protects entire corporate networks from potential cybersecurity threats. All traffic coming through a network with a Palo Alto NGFW matches against a security session, and each session is compared with a security policy. Data must meet the requirements of the policy to pass through. Network administrators can configure Palo Alto firewalls using GTP stateful inspection, which offers protection against three types of traffic: control plane, user plane, and charging. 

Key features

  • Zero-delay signature updates
  • Inline deep machine learning (ML)
  • AIOps monitors firewall health to predict and remedy potential outages


  • Unparalleled product stability
  • Clear reporting
  • Easy-to-monitor network traffic
  • Real-time detection and monitoring


  • Expensive
  • Poor documentation
  • Some advanced features are hard to use


Palo Alto’s website includes an extensive library of hands-on demos, free trials, and personalized tours—or you can reach out to set up a direct consultation.

Check Point: Best for small and medium-sized businesses (SMBs)

Check Point has a full suite of NGFWs to choose from, offering stackable feature selections for businesses of every size. Quantum Spark is particularly tailored for SMBs, providing comprehensive, all-in-one security for small networks of under 500 users.

Key features

  • SandBlast Zero Day prevention
  • Unified management platform
  • Remote-access VPN
  • Hyper-scale networking


  • Easy centralized management
  • Scalable
  • Dependable packet inspection


  • Can be complex to configure
  • Pricing is not very competitive
  • Customer service could be improved


Prospective customers can request a demo from Check Point’s website, or talk to sales for pricing and other product information.

Other Notable Stateful-Inspection Firewall Vendors

A few other notable firewall vendors include:

  • Fortinet
  • Sophos
  • Juniper
  • WatchGuard

Consider using one of the vendors above to find the proper firewall for your company’s protection.

Who Should and Shouldn’t Use Stateful-Inspection Firewalls?

Everyone can benefit from the security offered by stateful-inspection firewalls. Firewalls are absolutely critical to protect businesses of all types and sizes from potential cyberattacks—and stateful-inspection firewalls are indisputably more effective than their older siblings.

However, they’re also typically more expensive than stateless firewalls, so not all organizations can feasibly afford a stateful firewall.

Small businesses with little or no sensitive data might want to leverage a stateless firewall for lower total cost of ownership (TCO). Large corporations with a vast network of employees, on the other hand, should strongly consider using a stateful-inspection firewall.

Bottom Line: Stateful-Inspection Firewalls Boost Security Posture

The cybersecurity landscape is becoming more threatening as more businesses make digital transformations. New technologies like AI, ML, and cloud-based networking are highly beneficial for companies, but they’re a double-edged sword. Using more technology means there are increasing opportunities for threat actors to exploit your network and target your organization in a malicious attack.

One step your company can take to protect itself is leveraging an NGFW capable of stateful inspection. Stateful-inspection firewalls offer top-tier protection for companies, especially those working with high volumes or highly sensitive data. By implementing stateful firewalls, your business can operate smoothly by preventing potential cyber attacks, which cause unnecessary downtime and can cost hundreds of thousands—or even millions—of dollars.

If you’re looking for a more comprehensive security package, here are the best network security companies to trust with your organization’s data.

Devin Partida
Devin Partidahttps://rehack.com/
Devin Partida is a contributing writer for Enterprise Networking Planet who writes about business technology, cybersecurity, and innovation. Her work has been featured on Yahoo! Finance, Entrepreneur, Startups Magazine, and many other industry publications. She is also the Editor-in-Chief of ReHack.

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