UPDATED February 10, 2022 This piece has been updated to reflect the emergence of new technology

This image has an empty alt attribute; its file name is Untitled-design.jpg

Christian Mathews Security Writer

You might be familiar with the term ‘firewall’ as you’ve probably seen it on your computer. It’s a system that protects your computer or a network of computers. But what do firewalls do to protect a computer or a network?

We will be answering this question as simply as possible and explain more about firewalls in detail in this post.

What Do Firewalls Do?

In simple terms, a firewall acts as a filter for signals coming in and out of a computer or network. The internet is publicly accessible to all. For most people, internet accessibility is mostly about browsing websites. However, someone with sufficient technical expertise can gain access to any computer/network that is connected to the internet.

By connecting your computer to the internet, a networking expert uses that connection to get into your computer. A firewall prevents such things from happening. It blocks online intruders and any harmful information on the internet before it enters your system.

What Can A Firewall Protect Against?

A firewall protects computers against anything that its security rules order it to. These ‘security rules’ are a set of instructions that tell the firewall what it should allow into the network.

If you use a computer at your home, you might have noticed an in-built firewall software. Such in-built firewalls come with pre-set instructions to protect the computer against suspicious IP addresses, domain names, computer viruses (how do they work) and malware attacks. All you have to do is turn them on and let it do its job.

But if you have the required technical knowledge, you can actually customize the security rules for your computer’s firewall. In fact, that is what companies and organizations do. They don’t just rely on their computers’ in-built firewalls and turn it on. They have experts who manually set specific security rules to gain full control over what enters and leaves their network.

So, to sum things up, firewalls generally protect computers against suspicious IP addresses, hackers, viruses, and malware attacks. The network administrator can deny access to any information that they don’t want inside their network.

How Does A Firewall Work?

As we have already established, a firewall works based on the security rules defined for it. You define these rules by the following criteria:

IP Addresses

A firewall allows and blocks any IP address from entering a network. You can configure only specific IP addresses to enter the network while blocking the rest. Alternatively you can allow all IP addresses but block specific ones.

Domain Names

Similar to IP addresses, firewalls can also allow and block traffic from specific domain names.


Protocols are a set of instructions that control the transmission of data and communication. It does this between multiple computers and devices that share the same network. You configure a firewall to permit or ban specific protocols. If you ban the File Transfer Protocol (FTP) on a specific network, it will not permit files uploads or downloads from that network.

Ports and Keywords

Firewalls also block certain ports and even keywords. In the case of keywords, you should know that firewall will only block the information if it has the exact match of the keyword. It requires the exact spelling including any symbols such as hyphens.

How Does A Firewall Protect A Server?

A firewall protects a server by filtering out unauthorized users and harmful information. The level of protection varies for general home-use computers and organizations.

For Personal Computers and Devices

When we activate the in-built firewall in our personal computers at home it protects us by blocking sites that don’t have a security certificate or potential malware. The routers that you use at home can also have firewalls installed in them. That way any device that uses the internet through that router will be protected automatically.

For Corporations and Organisations

The main use of firewall for large organizations is to protect their system and network. They protect from a number of threats and keep their data private and confidential. For example, they may ban all IP addresses and only allow IPs from their clients into the system. This is how you maintain a private network while connecting to the internet. With a firewall, organizations have full control over who can access their network and what goes in and out of the network.

Types Of Firewalls

There are mainly two types of firewalls:

Host-Based Firewalls

A host-based firewall you install on a single device and only protects that device. The in-built firewall in your computer is an example of this. It only protects your computer and has nothing to do with other devices.

Network-Based Firewalls

When you install a network firewall on the entry point of the network itself, you protect every device that is connected to the computer. An example of this is the firewall installed in a router. It protects every device that connects to that router.

What Happens If You Don’t Have A Firewall?

You find firewalls in almost every computer and used by all organizations. This is because they are not just an option but a necessity.

If you don’t have a firewall on your home computer, it won’t block harmful sites. You may end up downloading a file that is infected by malware or may fall prey to phishing attacks that leak your private information to hackers.

For companies, the absence of a firewall security means that anyone with some networking expertise can access their system and files. Any computer in the company that is connected to the internet but doesn’t have a firewall becomes accessible publicly, as well as equally susceptible to hackers and malware, which can prove to be devastating for the company.

What Firewall Protection Do I Need?

For general home-use computers, you don’t need a high level of protection. So a simple host-based firewall like the one pre-installed in your computer should be enough. If you desire better protection, then purchase the best router for smart home that also has a firewall installed in it. This way, not just your computer will be protected. Any device such as phones and tablets that connects to your home Wi-Fi through the router will be protected by its firewall too.

For organizations, it’s essential to ensure maximum security. Smaller organizations mostly need a secure network-based firewall at the very least. If they have multiple networks and each requires a varying level of security, they can install separate firewalls for each network.

Larger organizations are recommended to go for double-layer protection. Using a network-based firewall in the main network while also using a host-based firewall in every device that is connected to the network adds this extra security layer.


The internet is just as much dangerous as it is useful. The level of threat is particularly higher for businesses and organizations. But even your home’s internet and personal computer are not safe from the perils of online intruders. That’s why every device that uses an internet connection must have an active firewall at all times. Especially now that you know what does a firewall do and how it can help protect you.