Understanding the Basics of Firewalls

Hardware firewall

Firewalls, we have all heard about them, but what are they actually and what do they do? This short post will explain the basics of firewalls. After reading this, you will understand what firewalls do and what kind of firewalls are out there.

Firewalls explained – what do they do?

Firewalls are a protection method for personal computers and networks. They can be described as a wall that blocks malicious or unnecessary network traffic from getting in and out. Firewalls are protection against malicious traffic and they do not protect against malicious files sent via email or malware downloaded by the user.

As simple as they sound, firewalls have a lot of different functions and they can be built for specific purposes. Firewalls can be configured to block data from some specific location or network and they can make your network or computer inaccessible for malicious software on the internet.

Let’s go just a little further, firewalls can be used to restrict the use or functions of a specific program or application or close specific ports on a computer or router while still allowing all the necessary data to flow without interruptions.

In a nutshell, firewalls are used to allow and disallow network traffic, communications of a computer or installed software. The user can modify the firewall rules to match their needs. However, the default rules are all a normal user needs and if you are not sure what you are doing, it is better to leave the firewall rules alone.

Different types of firewalls

As mentioned before, the firewall can block incoming or outgoing network traffic, but also the communications of a specific application or malicious software that is sending or receiving malicious content.

As there are different uses and configurations for firewalls, there are also different places the firewalls can be implemented. Therefor we have hardware and software firewalls, as they both have their use cases.

Hardware firewalls

Hardware firewalls are also knowns as network firewalls, are easy to understand, it is a separate physical device. In company networks, it is a device which job is to filter the traffic in the network and drop internet traffic that is not allowed. The firewall is placed on the edge of the network, so disallowed traffic is dropped before it enters the network.

In home networks, the router usually has a firewall implemented in it. It works in the same way as the firewall in company networks but it commonly isn’t as configurable as the completely separate firewalls.

Hardware firewalls are useful when you want to protect a whole network from unwanted or possibly malicious traffic. They also add an additional line of defense as the unnecessary traffic does not reach the actual computers in the network. The maintenance and configuration of especially the company network firewalls requires a professional and they can be expensive.

Software firewalls

Software firewalls are built-in features in computers and they do basically the same as the hardware ones, block traffic that is not allowed. It is just a computer program running on your computer instead of a separate physical device. Software firewalls are also used in a slightly different way than hardware ones if we look at them in more detail.

Software firewalls differ in that they control the applications in a system. They can be used to block specific applications from connecting to the internet or control specific network behaviour of a computer.

The disadvantage of software firewalls is that they are on the same system they are protecting. If the system is in control of a attacker, they might be able to change the firewall rules making it useless. Another thing in a large corporate network is that if all the computers have their own firewall, the updating and managing of every single one of them can be a lot of work.

Hardware firewalls protect the whole network and software firewalls protect the computer it’s running on. When you have both of these, for example a router with a firewall and a computer with firewall enabled you are protected by two lines of defenses.

Firewall configuration

Basically, all of the firewalls for sale come preconfigured and ready to use as they are. It is important to still go through the configuration and alter it in case there is something to change. Different companies have different operations and network usage, so they need to customize the configuration to fit their needs. Home users can get far with the defaults but it is still advised to go through the rules to understand what is allowed and what is not.


Default settings are usually less restrictive and even though the firewall is properly configured, they don’t guarantee you are going to be completely safe. There are many ways your network or computer can be attacked, firewalls protect against malicious traffic, not programs or files that include malicious code.

Using a firewall with other protective measures will help you to keep your computer and network safe from different kind of attacks.

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PC Rookies is a project to share information related to mostly security related topics.

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