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Stateful Inspection. A stateful inspection firewall uses a technique known as stateful packet filtering to keep track of communication channels. This is different when compared to basic firewalls. Once the packet and connection has been sent, a normal firewall will not remember the communication channel, whereas the stateful inspection firewall will. This also proves useful to protect connectionless communication protocols.
Stateful packet inspection
The method you are referring to is called SPI - Stateful Packet Inspection. A firewall employing SPI is commonly called a stateful firewall.
logs stateful inspection
Firewalls perform a simple form of "stateful inspection" of the packets that flow through them.
Stateful packet inspection
Stateful inspection works at Network Layer . Many Thanks, Chinmoy Roy
stateful packet inspection
A network hub absconds with any stateful packet inspection (SPI), so it won't act as a firewall.
Access is permitted only if it is a legitimate response to a request from an internal host.
Stateful inspection firewalls monitor the state of active connections and use this information to determine which network packets to allow through the firewall. This is in contrast to static packet filtering where only the headers of packets are checked. Attackers can exploit this property of static filters to sometimes get information through the firewall by doing something like indicating "reply" in the header. Stateful inspection, on the other hand, analyzes packets all the way down to the application layer of the OSI model. Stateful inspection can monitor communications packets over a period of time and examine both incoming and outgoing packets. Outgoing packets that request specific types of incoming packets are tracked and only incoming packets that are proper responses are allowed through the firewall. In a firewall that uses stateful inspection, the network administrator can set the parameters to meet specific needs, for example ports can be closed unless an incoming packet requests connection to a specific port and then only that port is opened. This practice prevents port scanning, a well-known hacking technique.
Stateful Packet Inspection of the traffic entering the device. It cannot inspect on outbound traffic.