What is a firewall and what does it do for your security?

When your computer is connected to the internet, it is vulnerable to cyberthreats – hackers out to steal your sensitive data as well as malware such as ransomware or Trojan horses. However, the good news is there is a way to guard your device and its data from unwanted access: A firewall.
Today we answer all your questions about firewalls and why they are important.

by Alyssa Schmitt
Woman’s hands typing on laptop
Surf the internet more securely with a computer firewall

Firewall meaning

In computing, a firewall is a security system that filters incoming internet traffic to your computer or private network. The word is borrowed from the older idea of a “fire wall” – a physical barrier that protects buildings from the spread of an actual fire. Similarly, a computer firewall stops or slows the spread of online threats, like viruses or hacking attacks. Firewall protection can be provided by software, hardware, or a combination of both.

What does a firewall do?

If your computer is connected to the internet, it is vulnerable to cyberattacks. A firewall protects your computer or network from malware and data theft by monitoring external traffic that tries to access your operating system. You can picture the firewall as a gatekeeper to your private network: It analyzes incoming data packets and either blocks them or lets them through based on whether or not they represent a threat.

How does a computer firewall work?

A firewall regulates the flow of data at the entry port of your computer or private network, where all internet traffic passes through. It is configured to allow or deny data packets based on certain criteria – in other words, to filter out the good from the bad.

A firewall applies pre-set or dynamic rules to determine if the source that is trying to access your computer is trustworthy or untrustworthy. There are several different types of firewalls that differ in terms of their exact setup and functionality, but generally speaking, a firewall will filter incoming traffic based on a combination of:
  • Traffic source (based on IP addresses)
  • Destination
  • Contents
  • Packet protocols (e.g., TCP)
  • Application protocols (e.g., HTTP)
Illustration of computer firewall
A firewall guards your computer or network from incoming threats

Types of firewalls for home use

Firewalls can come in the form of either hardware or software, and if you have a somewhat new computer and Wi-Fi router in your home, you probably already have both:
  • Hardware firewall: The router that provides internet access in your home or office serves as the gateway between the internet and your computer(s). For this reason, today most routers include firewall features. This provides a line of defense in addition to any firewall software on your computer. There is also separate firewall hardware that can be purchased for home use, but they often require some expertise to configure and maintain.  
  • Software firewall: Whether your computer runs the Windows or MacOS operating system, all recent versions come with preinstalled firewall software. You can also purchase separate firewall software, either as a dedicated solution or bundled with antivirus software.

Do I need a firewall for home use?

If you surf the web, you need a firewall! When you connect your personal computer or network to the internet, you are opening the door to a variety of cyberthreats, including getting malware or ransomware on your device – not to mention identity theft and other forms of online fraud. Without a firewall, you are basically leaving the gate to your home open with no one to guard it.

However, this does not necessarily mean that you need to purchase additional firewall software or hardware – as already discussed, you probably already have firewall protections on your computer and router, and you may also have additional firewall features bundled with an antivirus program. What’s important is to make sure that your existing firewall protections are activated and up to date.

You may need to purchase additional firewall protection if you have an older router, or if you are using an older operating system that is no longer supported by the manufacturer. Older hardware may not include firewall features, while older software might not be receiving regular updates that let it adapt to current cyberthreats. Unfortunately, having dated devices can leave you vulnerable unless you take precautions.

How do I make sure my firewall is on?

Although a firewall is a standard component of most routers and computer operating systems these days, it won’t protect you unless it is activated! The Windows firewall should activate when you first start up your computer, and it will notify you if it is deactivated. In contrast, the MacOS firewall is not activated by default. And while most wireless routers contain a built-in hardware firewall, the default activation settings will vary based on the manufacturer and model.

So, how do you know if you have an active firewall on your device?

Checking your firewall settings on your Windows computer

The preinstalled firewall program on your Windows computer is called “Windows Defender Firewall”. You can find it under System and Security in your control panel, or you can simply type “Firewall” into the search bar of your Start menu.
  1. Go to the Windows Firewall option.
  2. You should see two categories: Private networks and Guest or public networks.
  3. The green shield icons next to each firewall indicate they are active.
  4. This is also where you will find Advanced Settings if you’d like to view or change your firewall’s filtering rules.

Checking your firewall settings on your Mac

To see your firewall settings, click the Apple icon in the top corner of your screen.
  1. Open the System Settings menu and click Network > Firewall.
  2. Depending on the version of MacOS you use, you may instead need to go to System Preferences > Security & Privacy > Firewall.  
  3. If you see the setting “Firewall: Off”, click “Turn on Firewall” to activate it.
  4. Advanced settings are found under Firewall Options.

Checking your router’s firewall settings

The firewall settings will vary depending on your router, but it should be easy to locate them on the configuration page. Not sure where to find the settings? You can enter the router's IP address (e.g., 83.884.658.65) into the address bar of your internet browser to open its administration settings. Once on the configuration page:
  1. Locate a setting labelled Firewall, SPI Firewall, or similar and click to open.
  2. If the firewall is active, it will be marked “On”, “Active”, or similar, or have a green checkmark or toggle.
  3. If it is not active, find an option such as Enable or Activate.
  4. Save or Apply the changes if prompted.

Firewall vs. antivirus – what is the difference?

Because there are computer security software packages that bundle firewall and antivirus features, it can be easy to assume that they are basically the same thing. However, they serve different purposes:
  • A firewall is software or hardware that is used to prevent unauthorized access to a computer or network by filtering data traffic to identify and block threats. Its function is to keep cyberthreats from entering.
  • An antivirus application provides protection from malicious software once it has arrived on your device by detecting, identifying, and removing malware. Its function is to quarantine or remove threats once they have entered the system.

Bonus explainer: Protect your home computer & network

Firewalls are essential to keeping your computer and private network protected against cyberthreats. However, making sure you have an active firewall is only one aspect of safeguarding your security:
  1. Make sure your firewall software is kept up to date. The same applies to other software and your device’s operating system. These security updates and patches help keep you safe from new threats and vulnerabilities. Learn more in our explainer: Software updates: Why they are important to your security
  2. Use a reputable antivirus protection program. Computer viruses and other malware may make it past your firewall, and antivirus software is needed to disable and remove these threats. Find out more about malware here: Malware types: Do you know the true meaning of malware?
  3. Protect your home internet connection by paying attention to the security of your Wi-Fi router, including changing the default passwords. Read more in our deep dive: Secure Wi-Fi router: 8 ways to keep your home network safe

Now you know all about the role firewalls play in protecting your computer from unsafe internet traffic. Before you go check that your firewall is activated, please leave us some feedback below!

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Images: 1&1/Shutterstock

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