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Stateful firewall

(also dynamic packet filtering)

Stateful firewall definition

A stateful firewall, also called dynamic packet filtering, is a network security system that monitors the operational state of active connections and makes decisions about permitting network traffic based on the state information. This is an improvement over stateless firewalls, which only look at individual packets in isolation, without context or understanding of whether they are part of an established connection.

See also: internet security, network security protocols, firewall, network intrusion protection system

Stateful firewall examples

  • Real-time traffic monitoring: Stateful firewalls are used to monitor ongoing traffic on a network, analyzing packet information in real time to make intelligent decisions about what traffic to allow.
  • Intrusion detection: They can detect unusual patterns or suspicious behavior, such as multiple failed login attempts from the same IP address, that may suggest a security breach or cyberattack.

Advantages and disadvantages of stateful firewalls


  • Enhanced security: Stateful firewalls offer improved security over stateless firewalls by considering the context of network connections, not just individual packets.
  • Efficiency: By keeping track of active connections, they can make faster decisions about what traffic to allow, enhancing network efficiency.


  • Resource intensive: Stateful firewalls require more processing power and memory to track the state of network connections, which can slow down network performance.
  • Complexity: They are more complex to configure than stateless firewalls, requiring a deeper understanding of network protocols and security concepts.

Using stateful firewalls

  • Ensure you have adequate system resources: Given their resource-intensive nature, make sure your system has the necessary capacity to handle a stateful firewall.
  • Stay updated with security best practices: Regularly updating firewall rules and staying informed about the latest security threats will help maximize the benefits of a stateful firewall.