Network Security Blog

packet filtering firewall
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-filtering the packet
packet-------ASA-------------packet
                    -checks set of rules/filters whether to allow or deny
                    -allow or deny based on src ip/port dest ip/port protocol type(tcp/udp)
-transport layer and network layer

statefull packet inspection
===========================
-same as what packet filtering does
-it does a deep packet inspection from application to network layer
-allow or deny based on established connection
-maintains state table for all connection.(remembering)
-this remembrance protects against attacks

application gateways/proxies firewall
=====================================
packet-------ASA(proxy)-------------packet
                    -when i rx any request ill see if Connection established if ok
                    then ill send a new connection to destination on behaalf of client
-there is no direct connection. it has through proxy
-layer 7

circuit level gateways
======================
packet-------ASA-------------packet

-it also does same type of inspection
-but once the session is established then all ports are opened,
-all packets are passed in that session untill the session is terminated
-layer4(transport layer)