A firewall is a security device that is implemented to ensure that no authorized person can access the network or breach it. It is an efficient security mechanism that IT Software Company should implement in their company. These are the security devices that can either be hardware or software. Firewalls can perform functions like monitoring the data in and out of the system. In other words, they check all the data packets that enter the system and that are sent out of the system. Firewalls are of different types, according to their type, they send, allow, reject or drop the data packets.

There are certain rules that are followed by the firewall. They are:
• Accept – The firewalls can accept the request if they want to allow the traffic.
• Reject – This is done when the firewall wants to block the traffic. But when they block the traffic, the replies with an “unreachable error” message.
• Drop – This is also done when the traffic needs to be blocked. But in this case, the firewall does not send any reply.

These are the three basic tasks that every firewall does on the basis of the default policy. Also, different types of firewalls have different security features depending on the type of firewall being used. It depends on the requirement of the company whether they want a firewall that is highly secure or they want a firewall just to monitor the traffic of the network. Before implementing a firewall, there are many factors that need to be considered. In this article, we will study different types of firewalls and how they work.

How Firewall Works

According to the security needs of the organization, a table is defined for firewalls. These firewalls work according to this table. The rules present in the table are matched with the network traffic and according to this, the rules are defined. For instance, rules specified for the HR department would be different as compared to the marketing department. An employee working for the marketing department cannot access the information of the employee working for any other department. Also, according to the other rule, the system administrator can access information of employees from all the departments. In this manner, rules can be defined as per the requirement of the company.

Traffic can either be incoming or outgoing from a server’s perspective. Usually, the server itself generates outgoing traffic, due to which it is allowed to pass. But it would be better if there are certain rules applied to this to ensure more security. In incoming traffic, three protocols of the transport layer reach thee firewalls. These are TCP, ICMP or UDP. These contain the address of source and destination. In ICMP, the purpose of the packet can also be identified.

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Types of Firewall and Working

These are the types of firewalls available:

1. Packet Filtering Firewall – According to the name, this firewall filters the packet that is incoming or outgoing. They use control network access. A data packet contains the header, message, source, and destination. Packet filtering looks only checking the packet header and according to the rules, it either forwards the packet or discards it. It does not check if the packet contains any malicious data or something similar.

Just checking the source and destination and whether it is allowed to access the network or not. Such firewalls are implemented in the system where it is not necessary to check the data. It provides security but a data packet with malicious content can also be passed through it. Hence, for better security, another type of firewall should be implemented.

2. Stateful Inspection Firewall – This has replaced the old packet filtering firewall. This is a more efficient version of the firewall. It not only checks the system but also checks the working of the system. In this way, it provides more security. A state table is maintained in this type of firewall. In this table, a track of network connections is kept. Therefore, the permission to the packet is not determined by only the rules defined in the table but it also depends on the history and state of the packet incoming and outgoing in the network. This makes it more secure than the traditional firewalls.

3. Application Layer Firewall – These firewalls work as a proxy server. There is no direct communication between any sides of the firewall. According to the predefined rules, the packet can either be blocked or allowed. This firewall can filter packets of any OSI layers up to the application layer. It also has certain features that contain blocking the specific content, identifying if the protocols are being used for malicious reasons or they are being misused. Hence, it is more secure and efficient to use. Some IT Software companies and other areas also use it as Network Address Translator (NAT).

4. Circuit Level Gateway – Another type of firewall is circuit-level gateway. In the OSI layer, there is a session layer, this firewall work on the session layer of the OSI model. This firewall works by looking after the TCP handshake. When the firewall monitors the TCP handshake, they try to identify whether the session being requested is legitimate or not. After checking this, the data is sent to a remote computer. In order to prove a certain session is legitimate or not, a set of protocols and session rules are checked. Details of the network are kept secured and hidden from the external traffic. This firewall also provides high security and is efficient.

These are the main type of firewalls. A firewall is an efficient security mechanism and each IT Software Company should establish and install a firewall in their organization. According to the requirement, the type of firewall can be selected and implemented.


About Author


I am Leeza Keen and I have worked for different IT companies in Ludhiana as Content Writer. I have a keen interest towards technology and educational niches. Hence, I write articles and blogs relating to technology.

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