Different Function of Firewall You Should Know


By Jack Lin

Update on

function of firewall
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On the surface, the firewall is a service that protects your computer from infected viruses from the internet or computers.

But if you dig a little deeper, you will soon see the different functions of a firewall does the real work by applying a unique method to evaluate these things on the internet before reaching a conclusion.

These functions of the firewall offer a lot to the table. This article will let you know all about the functions and how they work.

What is a Firewall?

A firewall works as a layer between your computer and every other thing that happens outside of your computer. It separates your computer from others sharing the same network and the internet.

Basically, it does a great job of protecting your computer from accessing everything directly from the internet or other computers.  That’s why the firewall is so important to the computer; without it, our computer would give out information without our knowledge.

A firewall evaluates every bit of information first before accepting those signals to your computer.

What is a Firewall

Types of Firewall

Not everything will be available in just one place. The same thing to the firewall; you are not going to get everything in only one platform. That is why there are two variants of firewalls you would normally see on a computer.

One refers to a software firewall, and the other is a hardware firewall. These two firewall system is what makes the function of the firewall works.

Besides, read more about the full stateful vs. stateless firewall comparison and information about the WSUS server and the best open-source firewalls.

Hardware Firewall

A hardware firewall provides all the things you need to keep your computer safe from all types of malware. Unlike a software firewall, a hardware firewall comes with a dedicated hardware device.

Since almost all of the data travels through the device, having a firewall inside of it helps the firewall; to sync faster than a software firewall. Hardware firewall filters the traffic much faster and with dead-eye precision.

The functions of a hardware firewall can put down any beginner who is trying to find their way out of the system. A hardware firewall offers much more to the table, but it is complex to get into. Every firewall piece must be configured before the user can utilize the service.

An experienced network administrator can only handle a hardware firewall as they would have the knowledge and training to go through the whole system without messing the firewall up and effectively run all the functions of a firewall.

Besides being complex and offering more functions of a firewall to the system, the hardware firewall can be very expensive compared to the software variant. Since you only get a hardware firewall in another physical device instead of getting it through software.

But if you want to keep your computer safe from all sorts of dangerous stuff on the internet, it is a very small price to pay for the security service you will get with this type of firewall.

By the way, here is full information about a full AES vs. TKIP comparison for your reference too.

Software Firewall

A software firewall will come installed on a computer as software than hardware by not having any dedicated device to utilize the firewall system fully. A software firewall doesn’t even come close to the functionality of a hardware firewall.

This type of firewall has access to all the resources that have a shared environment. When it comes to efficiency, it is slower compared to the hardware firewall. The limitation in features and functions is what lowers the rating for a software firewall.

What it doesn’t makeup in functions or power, it makes up in the installation. A software firewall provides a much simpler installation than a hardware firewall.

If you are a beginner just starting out in the network fire, you can easily configure the settings without scratching your head.

And another great thing about having a software firewall is the low amount of cost. Because these firewalls don’t come in a dedicated device, it’s just software, which lowers the network cost rather than raising it.

Also, if you are facing the Verizon WiFi not working issue, here are the top solutions for you.

What Exactly Do?

Basically, the functions of a firewall will evaluate every website before letting them enter your computer or network. Sounds simple, but thousands of things are going down behind the curtain — firewall filters all the networks by the conditions and rules.

If the website meets all the rules and conditions of the firewall, then the firewall lets them access your files and data. There are different levels of filtering systems in the firewall that check the legitimacy of the website.

Those three are packet-level filtering, circuit-level filtering, and application-level filtering. These functions of a firewall carry the entire operation on its back.

Packet Level Filtering

This is one of the functions of a firewall that make sure the data packets get sent and received by analyzing the address of the destinations. In a network, the network layer has two different types of forms to show their real address.

One is the IP address, and the other is the destination address. IP address paints a picture of where the data came from; the destination address shows where the data is supposed to go.

If you have a hardware firewall installed, then you can filter the data and block the IP address from ever sending data to your IP address. It totally depends upon the rules that have been set inside the firewall system.

If the user allowed another computer to connect to their computer, then the firewall wouldn’t provide any blockage in the transfer of the data.

You also have the option to block specific IP addresses instead of canceling out the entire communication for the computer. This helps if you are running a business. Blocking a specific IP address will put that IP address on the blacklist.

Packet Level Filtering

Circuit-Level Filtering

Circuit-level filtering uses transport layer filtering to filter the traffic that it receives. The transport layer provides port numbers to identify the destination location. This level of filtering features a three-way handshake process to evaluate the data.

This is where before the data reaches the destination, a short temporary connection gets made from the sender to the receiver address. A three-way handshake provides that guarantees data delivery without any interpretation.

It provides Segmentation, connection multiplexing, three-way handshake, sequencing and acknowledgment, and flow control through windowing before sending the data to the destination.

A three-way handshake features a connection-oriented protocol than a connectionless protocol. If you are new to networking services, you mightier not know about these protocols.

Simply, a connection-oriented protocol makes sure a connection has been made to the destination before sending the data.  The connection has to be in proper order before the destination computer receives the data.

Circuit-Level Filtering

Circuit-level filtering allows one computer to access specific data packages from the other computers. If the user configures the firewall rules and doesn’t want to give the user access to every tiny bit of file inside the computer, then you can configure the firewall to be specific with the data packets.

Circuit-Level Filtering

Application-Level Filtering

Application-level filtering has the highest level of security out of all the filtering systems mentioned above. Like every other filtering, application-level filtering also filters the traffic but does it through application layer protocol.

Some of the protocols you might know as Http and Ftp. That’s not only it. You can also log the traffic if you want to analyze the filter system later. This gives the user insight into the weaknesses and strengths of their rules.

When you configure a firewall using circuit-level filtering to allow traffic through a port, the firewall might allow traffic from other application that creates a proxy connection crossway the port.

In simple words, sometimes, another network will access your computer’s firewall system by another application because they would be sharing the same port. Tot prevent these from occurring in the field. You have the option of the firewall only accepting HTTP traffic from any other connection.

Application-Level Filtering

All p2p file systems will be denied as the firewall only accepts genuine HTTP traffic. At the same time, application-level filtering has many features compared to circuit-level and packet-level filtering.

Application-level filtering is very resource-intensive. It is not at all friendly to beginners; it requires a professional, experienced networker to configure each layer of application filtering before you can apply.

While you can find application-level filtering inside the software firewall, it is recombined to only use the service on the hardware firewall system.

Because a software firewall is not capable of running application-level filtering in the system, and if you manage to run it, it will slow down all the other functions of a firewall system.

Stateful Inspection

Suppose you have a hardware firewall installed in your household. Then you will be allowed to save each packet passing through the firewall.

Configuring the firewall will save all the information regarding the packets. You will get plenty of information out of it, which will help you and the firewall system to analyze further filtering packets based on the same system. If one type of file has the same information as the other type of file, then it will get blocked.

Normally, on the internet, many malware comes in different forms and sizes with different behavior patterns. One of the patterns is to show up as pop-ups carrying the same message constantly.

If you have configured your firewall system, you will have a much easier time dealing with these problems. The function of a firewall will carry all the hard work on its back as it would be configured to handle all sorts of tasks.

By knowing the information of each connection, the firewall would know what to do if an unusual number of connections are made to the same computer. Each server limits the number of requests it can handle at a time.

Suppose more than a limited number of requests get sent to the computer. Then the server would get crashed. This is where the hacker will hack into the system and take all the valuable information from the computer in a single minute.

Stateful Inspection

Stateful inspection prevents such a thing from ever occurring in the system. It will record the information about each connection made to the computer or server.

The information would carry all the information about the connection, such as IP address and destination address. If the firewall saw any reputation on the sender’s address, it might conclude that this connection was potentially harmful and shut the entire thing down.

FAQs (Frequently Asked Questions)

  1. What is a firewall? A firewall is a network security device that acts as a barrier between trusted internal networks and untrusted external networks, such as the internet. It monitors and controls network traffic based on predefined rules to prevent unauthorized access and potential threats.
  2. Why is access control important in firewalls? Access control in firewalls regulates network traffic, allowing only authorized users and services to access the network. This function helps prevent unauthorized access and potential security breaches.
  3. What is packet filtering? Packet filtering is a firewall function that examines each incoming and outgoing packet of data and determines whether to allow or drop it based on predefined rules. It helps prevent malicious traffic from entering the network and enhances network security.
  4. How does Network Address Translation (NAT) contribute to network security? NAT is a technique used by firewalls to hide the internal IP addresses of devices on a network. It provides an added layer of security by mapping multiple internal IP addresses to a single external IP address, making it harder for potential attackers to identify specific targets.
  5. What is stateful inspection in firewalls? Stateful inspection is an advanced firewall function that analyzes the context and history of network connections. It monitors the entire conversation between a source and destination and helps detect and prevent unauthorized access attempts and unusual traffic patterns.
  6. What is the role of intrusion detection and prevention in firewalls? Firewalls equipped with intrusion detection and prevention systems (IDPS) can detect and block malicious activities within the network. They analyze network traffic for known attack patterns or suspicious behavior and take immediate action to mitigate threats.


Now you know all the functions of a firewall and how it helps the computer from harmful things.

All the functions have different mechanics and ways of dealing with things. That makes each one of them very different, especially priority-wise.

It is now more important than ever to have some sort of defense system to shield your computer from all sorts of malware because the internet and users are getting bigger every day.

The rise of users raises the chances of getting hacked by notorious hackers sitting far away from your place. That’s why having a firewall is one of the best ways to prevent these hackers from getting sensible information out of your network.


10 years of experience in information and computer technology. Passionate about electronic devices, smartphones, computers, and modern technology.