Posted by : Raj Thakkar Sunday, 5 May 2013

                In previous post I have told you about role of firewall in security of local system or private network. Today I will tell you how firewall protects your local system or private network from internet attacks. Here I will discuss different types of firewall and their working. Basically firewall has two types one is packet filter and second one is application gateway. Here I will tell you how packet filters and application gateways are working.




                 In packet filters some rules are stored previously and whenever any packet comes from outside it applies those set of rules to incoming packet and on basis of rules it decides whether give permission for go inside or discard the packet. They also apply same action if packets are going outside from inside. Packet filters are also known as screening filter or screening router. Now you might be thinking that on which basis set of rules are defined. So let me tell you that set of rules are defined on basis of number of fields in internet protocol and tcp(transmission control protocol) or udp(user datagram protocol) header.  Packet filters are extremely fast during their operating speed. In this way packet filters are providing protection to the local system or private networks from outside network. But there is one disadvantage is that setting up rules is too difficult.




                Application gateway is one type of firewall which protects local system or private networks from outside network. It is also known as proxy server because it behaves like any proxy server and decides the flow of application.
               Circuit gateway is variation of application gateway. It establishes a new connection between remote host and itself. User is not aware about this connection and he/she thinks that he/she is directly connected to the remote host. Circuit gateway changes the ip address of end user and because of that source ip address are stay hidden from outside network. As per my opinion Application gateways are more secure then packet filters.
                So friends these are working of packet filters and application gateways. Stay in touch for more information on security. Have a nice day.  

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