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[ScreenOS] What is stateful packet inspection firewall?



Article ID: KB6285 KB Last Updated: 10 Dec 2020Version: 5.0

This article answers the question: "What is stateful packet inspection firewall?"




  • Stateful packet inspection

  • Stateful inspection

  • Dynamic Packet Inspection



Stateful or dynamic packet inspection firewall provides the following features:

  1. Maintains a table of active TCP and UDP sessions

  2. Examines the contents of IP packets and forwards or drops the packet based on the set criteria

  3. Keeps the state of IP communication based on numerous fields in an IP packet (ex. Port number, flag)

    • New communication is examined then added to a state table.

    • IP packets not initiating a communication are permitted only if associating with a previously established communication.

  4. Is more secure than packet filters

  5. Is faster than application proxies (*Note:  Application proxy may provide higher level of details than stateful Inspection Firewall). 


Modification History:

2020-12-10: Removed EOL devices from product categories


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