How do stateful inspection and packet-filtering firewalls differ?

How do stateful inspection and packet-filtering firewalls differ?

In what scenario should a stateful inspection firewall and a packet-filtering firewall be used?

    Requires Free Membership to View

    SearchSecurity.com members gain immediate and unlimited access to breaking industry news, virus alerts, new hacker threats, highly focused security newsletters, and more -- all at no cost. Join me on SearchSecurity.com today!

    Michael S. Mimoso, Editorial Director

    By submitting your registration information to SearchSecurity.com you agree to receive email communications from TechTarget and TechTarget partners. We encourage you to read our Privacy Policy which contains important disclosures about how we collect and use your registration and other information. If you reside outside of the United States, by submitting this registration information you consent to having your personal data transferred to and processed in the United States. Your use of SearchSecurity.com is governed by our Terms of Use. You may contact us at webmaster@TechTarget.com.

In general, firewalls that make use of stateful inspection are the industry norm. Stateful inspection replaced packet filtering in most environments several years ago, and the majority of modern firewall systems take advantage of it.

The main difference between the two firewalls is that stateful inspection systems maintain a state table, allowing them to keep track of all open connections through a firewall, while packet-filtering firewalls do not. When traffic arrives, the system compares the traffic to the state table, determining whether it is part of an established connection.

The only place you'll likely see packet filtering in today's environment is at an Internet-facing router. These devices often implement a basic packet-filtering rule set to weed out obviously unwanted traffic and reduce the load on a stateful inspection firewall immediately behind the router.


More information:
  • Find out how implementing stateful inspection firewalls can help network administrators keep tabs on TCP connections.
  • You've learned about stateful inspection and packet-filtering firewalls. Now, see how these differ from proxy firewalls.
  • This was first published in October 2006