What Does a Firewall Do? | FortinetWhat Does a Firewall Do? And What Firewalls Don’t Do | Fortinet

Firewall Definition

A firewall is positioned between a network or a computer and a different network, like the internet. It controls the network traffic coming in and going out of the computer or network. If you do not have a firewall, virtually any data can exit your computer or network, and virtually any individual or program can come in.

A firewall is a security system designed to prevent unauthorized access into or out of a computer network. Firewalls are often used to make sure internet users without access are not able to interface with private networks, or intranets, connected to the internet.

Various Types of Firewalls

For example, if your personal computer does not have a firewall , viruses, malware, and hackers can have open access and even take over your device completely. In other instances, even if your computer is without a firewall, as long as the network it is attached to is protected, you can enjoy a degree of security because the firewall is still between your device and attackers on the internet.

What does a firewall do? The answer often depends on where it is and what it is supposed to protect. While all firewalls seek to protect your computer or network, there are different types of firewalls . What happens if you do not have a firewall depends on the attack surface the firewall is designed to shield you from.

What Does a Firewall Not Do?

Having a firewall does not necessarily protect you from all threats. There are several risks that can still impact your network. Malware is one of the most prevalent. Malware includes ransomware, viruses, worms, spyware, adware, pharming, phishing, and Trojan horses, each of which can be used to infect and control aspects of your computer. 

A firewall cannot always protect you from these threats because they often infiltrate your system through an email. Clicking a link inside the email causes the malicious software to be installed on your computer, thereby infecting it and possibly spreading to the rest of your network. Worms, Trojans, and viruses can all spread inside your network, infecting various computers. 

Trojans may come in the form of an application that appears to be harmless, but when you click on it, your system gets infected. A worm replicates on its own, spreading to other areas of your system, potentially inflicting significant damage. Similarly, a virus targets specific areas of your computer, resulting in crashes, insufficient memory, deleted files and programs, and more. If you have a firewall positioned before your wide-area network (WAN) but a computer that has accessed your WAN has one of these threats, you can be exposed.

Firewalls also cannot prevent unauthorized access to your computer. If your computer has a password, it is important to make sure you keep it private. A better defense is to use a hardware authentication device like a token. A user would need to have the token to get into your computer. If a malicious user gains access, they can abuse your device in any way they see fit. 

If a firewall is placed between where your computer connects to the network and the rest of the network, the attacker may not be able to use your computer to infect others on the network. In this way, a firewall can be used to segment the network. However, keep in mind that all devices within your segment can be attacked if an unauthorized user gains access.

A firewall also does not protect devices from physical theft or data leakage. For example, a hacker may be able to connect a universal serial bus (USB) device to your computer to track your keystrokes as you log in. A firewall cannot protect you from this kind of intrusion. Also, if your computer is stolen, a firewall will not be able to block a user from gaining access. You will have to rely on login credentials or multi-factor authentication (MFA).