It permits incoming packets that are legitimate responses to requests from internal hosts.
Stateful packet inspection
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 inspection works at Network Layer . Many Thanks, Chinmoy Roy
Packet Filtering:permits or denies traffic based onsource/destination IP addresses, or TCP/UDP port numbers usingAccess Control Lists (ACLs)Stateful Packet Inspection:Tracks TCP and UDP sessions in a flowtable, using the Adaptive Security Algorithm.
Yes it offers the staeful inspection.
Stateful packet inspection
dynamic state tables
logs stateful inspection
Deep packet filtering first examines the data part (and possibly also the header) of a packet as it passes an inspection point, searching for protocol non-compliance, viruses, spam, intrusions or predefined criteria to decide if the packet can pass or if it needs to be routed to a different destination, or for the purpose of collecting statistical information. This differs from "stateful packet inspection" (shallow filtering) where only the type of traffic and possibly the source and destination are inspected, not the contents of the traffic.
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.
Firewalls perform a simple form of "stateful inspection" of the packets that flow through them.
Access is permitted only if it is a legitimate response to a request from an internal host.