Firewall: Definition and Explanation

A firewall is software used to maintain the security of a private network. As quoted from Techopedia, Firewalls block unauthorized access to or from a private network and are often used to prevent illegal software or unauthorized WEB users from gaining access to a private network connected to the internet.

Firewalls can also be used for better security, because data can be encrypted. If you are experiencing security problems and are trying to protect important data in your company, maybe this firewall can be the right tool for the problem.

How does a firewall work? Basically, a firewall can do several things such as maintaining resources, validating access, acting as an intermediary, recording and reporting events, and managing and controlling network traffic. Not only that, firewalls have several methods including Packet Filtering, Application Gateway, Circuit-Level Gateway, Proxy Servers, and finally Stateful Inspection or Dynamic Packet Filtering.

What are the types of firewalls? Firewalls themselves have 3 types, namely proxy firewalls and next-generation firewalls (NGFW), packet-filtering firewalls, and stateful inspection firewalls. What are the three? Here’s the explanation.

Proxy firewalls and next-generation firewalls (NGFW) inspect packets at the application layer of the OSI model (Open System Interconnection reference).
Packet-filtering firewalls inspect packets separately and are unaware of the context of a packet.
Stateful inspection firewalls inspect network traffic to determine whether one packet is related to another.

Firewall Methods

1. Packet Filtering
   The first method is packet filtering. Packet filtering firewalls are the oldest and most basic architecture. As quoted in an article written by Eric Dosal, basically this packet filtering performs a simple inspection of data packets on routers and switches. Then, after that the information obtained such as port numbers, destination and source IP addresses, and other surface-level information is checked without opening the packet to check its contents. The final step is if the information packet after being checked does not pass inspection, then the packet will be discarded.
2. Stateful Inspection
   Next is stateful inspection or dynamic packet filtering. What is meant by stateful inspection? As quoted in Techopedia, this method compares the most important parts of inbound and outbound data so it’s not just header information. This is used to determine whether information is authorized to cross the firewall into the network. While Dosal said that this firewall method combines packet inspection technology and TCP handshake verification to create a greater level of protection.
3. Circuit-Level Gateways
   Circuit-Level Gateways function to verify TCP (transmission control protocol) handshakes because they are designed to ensure that a packet session is legitimate. This method is intended to easily and quickly approve or reject traffic without using significant computing resources.
4. Proxy Firewall
   The next method is a proxy firewall or application-level gateway. This method operates at the application layer to filter incoming traffic between the network and the traffic source. Then sent through another proxy device or cloud-based solution. The proxy firewall makes a connection to the traffic source and checks the incoming data rather than letting the traffic connect directly. This inspection is almost the same as the method in the second point, namely stateful inspection, but the difference is that this proxy firewall performs deep layer packet inspection, checking and verifying if the information packet contains malware.
5. Application Gateway
   The last method is the application gateway. What does it mean? This application gateway technique uses a security method. This method is applied to certain applications such as Telnet and File Transfer Protocol servers. To read other firewall methods, you can check this article: Firewall Method

As explained above, firewalls can be used as a tool to maintain the security of company data. To keep it working properly, you need monitoring for the firewall. However, monitoring the firewall itself is not easy. Why? This is because the firewall limits access to anyone who does not have a license or permission to use it.

To monitor a firewall, you need the right tool. One of the best is Netmonk. Not only can it monitor network devices such as routers, servers, switches, but Netmonk can also monitor the firewall of one of the hospitals in Indonesia. So, if you are interested and want to try monitoring your firewall, then Netmonk, a network monitoring application can be the right recommendation. If you are interested, please contact our marketing team here to get more information about products, solutions and other promotions. Hopefully this article is useful.

References:

https://www.techopedia.com/definition/5355/firewall

https://www.compuquip.com/blog/the-difference-types-of-firewall-architectures

https://personalfirewall.com/what-is-firewall.html

https://personalfirewall.comodo.com/what-is-firewall.html

https://www.techopedia.com/definition/5355/firewall

https://www.compuquip.com/blog/the-different-types-of-firewall-architectures