What is a Firewall ?
It is a barrier to keep destructive forces away from your property/assets. Its job is similar to a physical firewall that protects the fire from spreading from one area to another. It protects the network from unauthorized use by attackers. Basically, any device that can control network traffic for security is called a firewall.
What is a purpose of Firewall ?
The purpose of a firewall is to internally restrict one internal network from accessing another internal network. It also provides the log of the intruder’s attempt to access the computer network as providing their information such as date/time, IP addresses of intruders, and method of attack. For any unauthorized access, these computer firewalls protect us from it.
Types of Firewall:
Basically there are three types of firewalls which are as follows:
Packet Filletering :
This type of firewall system operates at the network layer or transport layer. In this routers examine every packet coming in and going out of an intranet and decide where to send those packets so that they can be delivered to the proper address. They can control the time & direction of the traffic permitted and essentially can also decide whether packets should even be delivered. In other words, they can block certain packets from coming in or going out of an intranet. When routers are used in this way to protect an intranet by blocking certain packets they are called filtering routers or screening routers. From a security perspective, ‘Filtering ‘ is a good concept. Filtering basically stops connections from or to the specific host or network. It can even block connections to a specific port. A packet filtering firewall, thus, looks at the data packet to get information about the source and destination addresses of incoming packets, the sessions communication protocol, and the source and destination applications parts for the desired services. a packet-filtering router can filter packets based on some or all the following criteria:
- Source IP address
- Destination Ip address
- Source Port
- Destination Port
Proxy :
Application layer firewall or also known as the proxy firewall has multiple interfaces, one for each network to which it is connected. Thus, an application-level firewall is commonly a host computer that is running proxy server software, which makes it a proxy server. This type of firewall functions by transferring a copy of each accepted data packet from one network to another thereby mashing the origin of data. This way services used by a workstation can be controlled. It also protects the network from outsiders who may try to get information about the network architecture.
Application gateways typically work as follows:-
- An internal user contacts the application gateway using a TCP/IP application, such as HTTP or TELNET.
- The application gateway asks the user about the remote host with which the user wants to set up a connection for actual communication.
- The user provides information to the application gateway.
- The application gateway now accesses the remote host on behalf of the user and passes the packets of the user to the remote host.
- The application gateway how acts like a proxy of the actual end-users and deliver packets from the user to the remote host and vice-versa.
Circuit Level:
It works on the session layer. This type of firewall is used for checking the user wants to establish the session is legitimate or not. This firewall also manages or control session on the server.