The firewall can be used for both hardware and software which helps in preventing malware and malicious attacks from entering a computer or a network of computers through the internet. The basic purpose of a firewall is to keep the uninvited guests from browsing your network. So, the firewall will allow you to establish certain rules to identify the traffic which can be allowed in or out of your private network. Just by depending on the type of firewall which can be implemented, neither we can restrict access to only certain IP addresses and domain names nor we can also block certain types of traffic by blocking the TCP/IP ports by using it. Below are the types of how does a firewall work.
A packet filter checks all the traffic to and from the network and gives it against the rules which we provide. So, the packet filter can evaluate the source IP address, source port, destination IP address and destination port. Also, there is a criterion that we can filter to allow or disallow traffic from certain IP addresses or on certain ports.
Circuit Level Gateway
A circuit-level gateway will blocks all the incoming traffic to any host but itself. The client machines will run the software to allow them to establish a connection with the circuit-level gateway machine. To the outside world, it appears that all communication from your internal network is originating from the circuit-level gateway.
A proxy server is put on the website to boost the performance of the network but it can act as a sort of firewall as well. So, proxy servers can hide your internal addresses then all the communications appear to originate from the proxy server itself. A proxy server caches pages that have been requested by the user. The other thing about the proxy server to block access to certain websites and filter certain port traffic to protect your internal network. By this Proxy server will help in how does a firewall work.
An application gateway is essential for the proxy server where the internet client first established a connection with the application gateway. Like the other proxy server types, the application gateway is the only address that is seen by the outside world and the internal network is protected.
The above-mentioned steps to help us in understanding about working conditions of the firewall. Hope that I have covered all the topics in my article about how does a firewall work. Thanks for reading!