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What is firewall
The name (firewall) has two terms fire and wall .According to name it means a wall which is in fire so as we know that no anyone can cross the wall of fire as like same no any unauthorized network can cross from firewall. In computing, a firewall is a network security system that monitors and controls all the incoming and outgoing network traffic based on predetermined security rules. Actually it establishes a barrier between a trusted internal network and UN-trusted external network, such as the Internet.
In computing, a firewall is software or firmware that enforces a set of rules about what data packets will be allowed to enter or leave a network. Firewalls are incorporated into a wide variety of networked devices to filter traffic and lower the risk that malicious packets traveling over the public internet can impact the security of a private network. Firewalls may also be purchased as stand-alone software applications.
Let us understand it by given picture:-
There are mainy four types of firewall :-
- Packet-filtering firewalls.
- Stateful inspection firewalls.
- Circuit-level gateways.
- Application-level gateways ( proxy firewalls)
Let understand it one-by-one:- *packet-filtering firewalls:-it is a firewall technique used to controls and monitors all the outgoing and incoming packets of data across network.it allowing some of them to pass which is authorized but denied some of them from pass because of unauthorized packets on the sources and destination internet protocol (IP) addresses, protocols and ports. As we can say that it is work as the security mechanisms. It is also know as static filtering Filtering rules are based on information contained in a network packet.
sources IP address.
Destination IP address.
Sources and destination transport level address.
IP protocol field.
Interface
* Stateful inspection firewall:-it is a network firewall that tracks the opening state or active connection and characteristics of network connection traversing it.only packets matching a known active connection are allowed to pass the firewall. It is also referred to as dynamic packet filtering ,is a security feature often included in business networks.
* Circuit-level gateways :- it is the another type of firewall which provides a system (UDP-User Datagram Protocol) and (TCP- Transmission Control Protocol) connection security .it works between the OSI models transport and its application layers such as the session layer.
* Application level gateways:- it is a firewall proxy which provides our system in network security. It filters incoming node traffic to certain specification ,in other words it only transmitted network application data is filtered .it include (FTP-file transfer protocol),(RTSP- Real time streaming protocol ) and BitTorrent.
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