What are Firewalls? Beginner’s Guide to Better Internet Security

If you’ve used the internet, you’ve probably heard about firewalls.

A physical firewall protects you and your property from danger. It also contains the destructive forces from further spreading out. In a similar way, firewalls for computers are barriers that protect you from threats on the internet

Firewalls also monitor and control data passing into your computer or network and can protect your computer with security software. You can think of it as a good wafer style butterfly valve that regulates the flow of fluids in a pipe. Or you can also think of your immune system that controls what enters into your body to prevent diseases.

In this article, you will learn more about how firewalls work and the different types of firewalls. This will help you better manage and protect your data and your computer.

What are Firewalls?

A firewall can be a software program or a hardware device. As previously mentioned, it acts as a barrier for the flow of data between a trusted network and an untrusted network.

A firewall system can differentiate between trusted and untrusted networks through predetermined security rules. If an incoming or outgoing packet of information meets the set criteria, it is allowed through. If the firewall examines the data and the filters are flagged, the data is discarded.

Firewalls definitely protect your computer from threats such as viruses, malware, offensive websites, and even hackers. But more than that, firewalls offer functionality in managing data. This is very important for companies that use multiple computers and employ numerous employees, each one sending and receiving files.

Different Types of Firewall Method

There are different firewall methods to control the traffic of data flowing in and out of the network. These methods can be used individually or combined into a firewall system:

Packet Filtering

Packets refer to small amounts of data. Packet filtering firewalls examine data as they try to go through a firewall. The packets are analyzed and compared against a list of predetermined rules called filters. Filters are based on the data source and destination. Packets that go through the filter are sent to the destination. Packets that don’t are discarded.

A packet filtering firewall makes it easy to block well-known ports and stop data from flowing in or out of a computer. Using this firewall method, you can disable all computers in the network to browse the web. Blocking information from coming into your network can be useful if you want to prevent unauthorized access to your website.

The limitation of a packet filtering firewall is that it only filters ports and IP addresses. It cannot analyze the content of the data packet.

Circuit Level Gateways

This firewall method acts as a gateway to the network it’s protecting. Those outside the network will only see the address of the firewall; the gateway protects the address of the rest of the network.

On a circuit level gateway, computers inside the network make requests for data. The firewall keeps a record of these requests and only data that matches with the requests are allowed inside the network.

The major advantage of a circuit level gateway method is the simplicity that all data from outside the network without a request will not be allowed in by the firewall, which is acting as a gateway. The main disadvantage is that it does not provide any control for data going out of the network unless it is combined with other firewall methods.

Application Level Gateways

Application level gateways are more commonly known as proxies. This method is similar to circuit level gateways but differs in the way that the firewall handles information.

An application level gateway examines the content of the data in addition to the address and port information contained in the data received. This makes this firewall method more comprehensive. For example, with an application level gateway firewall you don’t just control which computers in your network can browse the web, but you can also specify which web pages they are allowed access to.

This higher level of control makes application level gateways very secure. A disadvantage of this method is that the information passes through the firewall at a slower speed because the data has to go through proxy applications.

Stateful Inspection

The stateful inspection method is a newer firewall method. It is a mix between the packet filtering and gateway methods.

Similar to packet filtering methods, the state inspection method analyzes data passing through the firewall and compares it to a database of trusted information. The filter in this method analyzes more than just the ports and IP addresses, making it better than simple packet filters. 

However, this method also doesn’t analyze the content of the data as comprehensively as gateway methods. Stateful inspection filters only examine key parts of the packet. This combination of elements from both packet filtering and gateway methods goes away with the need for proxy applications, making data pass in and out of the network faster.


Gaining a better understanding of how firewalls work will help you make the most out of your computer and internet security system. There are different methods and combinations for firewall systems, each one with its own advantages and disadvantages. The firewall method that will work best for you will depend on how you want the information to move in and out of your network.

Adam Hansen

Adam is a part time journalist, entrepreneur, investor and father.