Firewall

Firewalls are devices designed to filter all incoming and outgoing network traffic through certain filters, aiming to stop malicious activities within network traffic.

Questions like "what does a firewall do" are often researched topics. To briefly answer the question of what a firewall is and what it does, the answer can be given as "a mechanism that blocks traffic that does not comply with the rules specified on the firewall".

Computers connected to a network are under many viruses and attacks. This is where firewalls come into play to prevent them. Firewalls, by entering between the computer and another network, control incoming and outgoing network traffic. In this way, software on the computer cannot provide information without our permission, network security is achieved. So the main goal of the firewall is to allow harmless traffic and keep dangerous traffic outside.

Firewalls act according to predetermined rules to better protect your network. Firewall directs traffic within these rules. Behaviors that comply with these rules are allowed, while behaviors perceived as threats are blocked from the network. Therefore, it is an important element in corporate security defenses. Large businesses with many users often use a Firewall device.

The speed and type of the Internet and the number of internet lines affects the choice of firewall device. Firewalls have become popular in the complex internet world over the years. Nowadays, these firewalls are now available with features such as IPS, IDS, Web Filtering, Application Filtering, Hotspot, VPN, and 5651 Log Management.

Why is Firewall Needed?

Answers to the question "Why should I use a firewall?" can be given as:

Legal Obligation: Law No. 5651 "Law on the Arrangement of Publications Made on the Internet Environment and on Combatting Crimes Committed by These Publications" states that using a firewall software is mandatory. This law states that if a crime is committed on the internet using your network and you own a business place, you need to use a firewall to prove that you are not the perpetrator and to protect yourself from cyber crimes.

Prevention Against Threats: You can block malicious software in the internet world full of viruses and attacks using a firewall.

Email Security: There is a lot of email traffic within the company and even with customers. In such a case, blocking malicious software that can come via emails is left to firewall mechanisms.

Site Access Restriction: You can block access to these pages by specifying the sites you do not want the staff to enter on the firewall. By blocking inappropriate content, you can use the internet for your purpose.

Firewall Usage Areas

• Firewalls are used by companies. They are installed on the network perimeter of organizations against threats that can come both from inside and outside.
• Firewalls can be used in a home network, on Digital Subscriber Line (DSL) or on cable modems.
• Home appliances can use firewalls to make restrictions. They are often used alongside antivirus applications.
• Firewalls are often preferred in financial and government agencies where data is important.

What are the Types of Firewall?

Firewall systems are divided into 2 main categories based on their structure and architecture.

1. Firewalls according to their structure

According to their structure, the firewall is classified as hardware firewall and software firewall.

Hardware Firewall Products

A hardware firewall is a term used to describe the integrated state of firewall security software into hardware such as the router. It controls the traffic between the internal and external networks using the method of packet filtering with predetermined filters. If it is suitable, it transmits to the network, and removes it from the circuit when it detects malicious software.

Since they work as a separate hardware from the current system, they do not affect your system's performance and speed. They also significantly reduce costs. However, the interface of some devices is complex and can be challenging, especially for new users. In this case, you can use management panels with easy interfaces like next-generation Firewall devices and UTM devices.

Software Firewall Products

This is the kind of firewall that does not require any hardware to operate, working on the application layer of operating systems and managed by being installed on the computer. So they can run as software on any computer.

It allows for control of incoming data to the computer. Since it does not require additional hardware, its costs are very low. If there is a firewall requirement in places with a small number of computer networks, this firewall will be an ideal choice.

It has a simple interface, its installation and use are simple, and users can perform their operations quickly. The disadvantages of these firewalls are that they can be easily disabled by users. Furthermore, they also put a load on the network as they continually run in the background, leading to network slowdowns.

2. Firewalls according to their architecture

Firewalls by architecture; are divided into four categories: static packet filter firewalls, circuit level firewalls, dynamic packet firewalls, and proxy supported firewalls.

Static Packet Filter Firewalls

Static packet filter firewalls read the header part of the incoming data, and evaluate the basic information. However, its weakness is that it is not interested in the content. Since it does not care about the content, it can allow viruses to enter the computer even from servers of safe technologies like Google. It checks data such as the source of the traffic, the destination address, which port it wants to access, and the protocol it will use. If it fits with the filters that have been previously determined, it allows traffic.

Circuit Level Firewalls

Circuit Level Firewalls, also known as circuit-level firewalls, check whether the incoming packets are data or connection packets. When traffic comes to a network, it first checks the source of the traffic, the port it will go to, and the protocol it wants to use. So in the first stage, the IP address does not tell the source of the traffic. The information of the IP address is shared only if everything complies with the filters. It does not control the content of the traffic like the static packet filter firewall.

Dynamic Packet Filter Firewalls

The Stateful Inspection or dynamic packet firewall, examines and checks the source of the traffic. Unlike static packet safety conditions, it controls the content of the traffic. Thus, extra security measures have been taken. One of the advantages of choosing this packet is that the port is open only when a request comes in and permission is granted. This firewall was designed due to the inadequacies of static packet filter firewalls.

Proxy Supported Firewalls

This firewall examines the source of traffic outside the network, and after content control, allows transition to the network if it is deemed appropriate. Proxy supported firewalls form a wall between the target and the source, that is, security control is carried out outside the network. Each incoming and outgoing message to the network is examined. Thus, the system is protected against malware.

Because it performs security control between the target and source, its speed is slow, and it causes performance losses. Therefore, it is not used in networks with heavy traffic. It is used especially in financial institutions and government offices where data security is important.