Stateful Inspection
Also referred to as dynamic packet filtering. Stateful inspection is a firewall architecture that works at the network layer. Unlike static packet filtering, which examines a packet based on the information in its header, stateful inspection tracks each connection traversing all interfaces of the firewall and makes sure they are valid. An example of a stateful firewall may examine not just the header information but also the contents of the packet up through the application layer in order to determine more about the packet than just information about its source and destination. A stateful inspection firewall also monitors the state of the connection and compiles the information in a state table. Because of this, filtering decisions are based not only on administrator-defined rules (as in static packet filtering) but also on context that has been established by prior packets that have passed through the firewall.
As an added security measure against port scanning, stateful inspection firewalls close off ports until connection to the specific port is requested.
Check Point Software is credited with coining the term stateful inspection in the use of its FireWall-1 in 1993.
Read Also:
- stateless
(adj.) Having no information about what occurred previously. Most modern applications maintain state, which means that they remember what you were doing last time you ran the application, and they remember all your configuration settings. This is extremely useful because it means you can mold the application to your working habits. The World Wide Web, […]
- statement
An instruction written in a high-level language. A statement directs the computer to perform a specified action. A single statement in a high-level language can represent several machine-language instructions. Programs consist of statements and expressions. An expression is a group of symbols that represent a value.
- static
(adj.) Generally refers to elements of the Internet or computer programming that are fixed and not capable of action or change. The opposite of static is dynamic. A Web site that is static can only supply information that is written into the HTML and this information will not change unless the change is written into […]
- Static NAT
(stat´ik nat) (n.) A type of NAT in which a private IP address is mapped to a public IP address, where the public address is always the same IP address (i.e., it has a static address). This allows an internal host, such as a Web server, to have an unregistered (private) IP address and still […]
- static routing
Static routing, the alternative to dynamic routing, is the process in which the system network administrator would manually configure network routers with all the information necessary for successful packet forwarding. The administrator constructs the routing table in every router by putting in the entries for every network that could be a destination. Static routes to […]