Firewall is a system that examines data packets over a network connection and allows or blocks the passage of these packets through the network according to the specified rules. Firewalls can be used as both software and hardware and generally act as a barrier between the internet and the internal network. In this way, only authorized users are allowed to access the computer or server system, while unauthorized access is prevented.

Firewalls are basically divided into two categories: Hardware-Based Firewalls and Software-Based Firewalls. Hardware-based firewalls are installed as a physical device and filter network traffic. Software-based firewalls, on the other hand, work on computers or servers and perform the traffic filtering process.

How Does a Firewall Work?

The main purpose of a Firewall is to ensure that data coming over the network is transmitted securely and to block traffic that threatens security. The working principle of firewalls is based on analyzing incoming and outgoing data packets within the specified rules. These rules are usually configured based on features such as IP address, port number, and protocol type. The working steps of a firewall can be summarized as follows:

1.Packet Filtering

The first step of a firewall is to examine data packets. Each incoming or outgoing packet is filtered by considering parameters such as source IP address, destination IP address, port number and protocol information. The firewall allows packets with allowed protocols to pass, while blocking other packets.

2.State-Based Filtering

Modern firewalls examine not only the content of packets, but also the state of the connection. State-based filtering allows the firewall to keep track of the state of each connection. Thus, only legitimate connection requests pass through the network, while suspicious connections are blocked. This filtering method allows the firewall to detect malicious traffic more accurately.

3.Providing Proxy Service

Some firewalls act as an intermediary between the client and the server by providing a proxy service. A proxy firewall hides the identity of the client and allows it to go out to the outside world, while at the same time filtering data packets to prevent malicious content from reaching the network. This is especially important for protecting users on the network against phishing and other social engineering attacks.

4.Application Layer Security

Advanced firewalls analyze not only at the IP and port level, but also at the application layer. Such firewalls limit the permitted use of certain applications or protocols. For example, they can be configured to allow access only to certain websites or applications. This type of security measure is especially preferred in business networks to ensure the protection of critical data.