MTE Explains: How Firewall Works (Windows)

While firewalls are not particular to the Windows operating system, many Windows users feel the utter need to use a firewall. However, they don’t know enough about how it works to tell what it’s doing for them. If you’re wondering what makes a firewall tick and how it’s protecting your computer, this article is for you.

Why Use a Firewall?

The purpose of a firewall, as the layman might explain, is to “protect the computer from attacks.” However, the purpose goes much deeper than that while holding onto that one principle. A firewall will ward off any attack at the point in which it starts. This means that if a website starts to send harmful data to your computer, your firewall detects it and prevents the website from loading. Company firewalls might even take this one step further and also block certain websites that the company doesn’t want you to see while you’re at your desk.


Firewalls have had a brief history in the evolution of the Internet, but they’ve gone from being tools that only corporations use to necessities in the home within a short period due to the multiple attacks that hackers launch on people’s computers on an everyday basis.

Do I Still Need an Anti-virus?

An overwhelmingly large amount of households use anti-virus solutions that scan their computers regularly for infections. People might think that a firewall prevents infections from happening in the first place, but this is a common misconception that might lead some to abandon their anti-virus programs for the quiet comfort of running Windows Firewall. This can ultimately lead to disaster, since a virus and a Web attack are two totally different things and should be treated as such.


A virus is a small bit of executable code that poses as a legitimate program. Viruses usually come in the form of “.exe” files and appear harmless until you open them. You might not even be aware of the infection, and a hacker may have access to tons of private data that you have. We’ve already covered viruses here.

A Web attack, on the other hand, is a piece of harmful data sent to your computer with the intention to either disable your computer’s Internet connectivity (by bombarding it with “packets”) or grab information from it that could possibly assist a hacker in compromising your system. These attacks usually don’t show any sign of infection when they happen, and can succeed in less than a second. Their effects are far more devastating, in some cases.

A good thing to keep in mind is that viruses are programs that detect executable code already in your computer while firewalls are programs that filter data sent over from the Internet.

How Do Firewalls Work?

A firewall keep track of all the incoming and outgoing IP addresses. By setting up a set of rules stating which IP addresses are allowed, the Firewall can block all other unauthorized access to your computer. In addition to blocking IP addresses, it can also block ports or restrict an application from receiving and sending data over the web.

How do I know if my Firewall is enabled?

In Windows 7, you just have to go to the Control Panel and search for “Firewall”. Click the “Check Firewall status”.


From here, you will be able to see if your Firewall is activated. You can also deactivate it if you want, or even configure it for better security. One thing though, you won’t want to configure it until you can’t access the Internet at all. The default settings usually suffice.

Any Questions? Comments?

If you have anything to contribute to this discussion, go ahead and leave a comment below. If there are any questions, there’s a button on the right-hand side of this site labeled “Ask Our Experts Now!” just for you. We publish the question (and its answer) weekly on our “Ask MTE” series.

Image credit: Virus Alert by Big Stock Photo.

Miguel Leiva-Gomez
Miguel Leiva-Gomez

Miguel has been a business growth and technology expert for more than a decade and has written software for even longer. From his little castle in Romania, he presents cold and analytical perspectives to things that affect the tech world.

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