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The firewall: the guardian of the border between your computer and the network

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What is a firewall?
Firewall: how it works
What types of firewalls are there?
How do you activate a firewall?
Does the home user need a firewall?


The firewall: the guardian of the border between your computer and the network

Everyone knows the term firewall or firewall. However, few of us are able to explain what it is and how it works exactly, although most of us know that it is a method of protection against viruses and other malicious programs from the Internet. Above all, home users are often unaware that even the best firewall can be useless if it is not configured according to user behavior or, worse, is not enabled. Find all the information you need to get the most out of your firewall..

  1. What is a firewall?
    1. Does the home user need a firewall?
  2. Firewall: how it works
  3. What types of firewalls are there?
  4. How do you activate a firewall?

What is a firewall?

In Spanish, firewall is translated as firewall. Therefore, it is very clear what it is about: to protect against damage from the outside. If we apply it to computing, it means that the computer is protected against the dangers that lurk from the Internet or other networks . These threats are usually, for example, malicious software, also known as malware. These are viruses or spyware ( spyware ) that can infect or enter your computer to collect sensitive data, modify it or alter certain system functions, even completely paralyzing the operating system. A firewall can prevent this from happening.

The firewall is, by definition, a kind of inspection body connected between the Internet or another network and the local computer. Check the access rights of remote computers and programs in both directions. The firewall settings determine whether the programs installed on your computer can access the Internet and vice versa. The firewall also regulates communication between the computer and other computers within a network..

Does the home user need a firewall?

We continue to ask ourselves this question because, in the beginning, firewalls were installed exclusively on networks with very high security requirements, such as those of government institutions, banks and large corporations. Today, these types of networks are protected by high-performance hardware firewalls.

Home users do not need such a high level of security and it would also not be affordable for them. However, the expansion of the Internet has led to an increase in the number of home computers infected by malicious software and, therefore, solutions for desktop computers have been developed that are already standard in most operating systems. This internal firewall should protect your PC , as viruses and Trojans are not lacking in the network with sensitive data in the spotlight..

Firewall: how it works

By definition, a firewall is there to protect your computer from any attack. But how is this in practice? How does the software know which program is malicious and which is not? And how do you discover that newly programmed malware is taking action?

First of all, it is important to know that the firewall does not recognize whether the access is hostile or harmless. Only, monitor your PC's access to a network and vice versa. The firewall then decides if one of these accesses is dangerous based on a series of pre-established rules .

The schematic shows in a simple way how a firewall works, monitoring data traffic and repelling suspicious access attempts.

User configuration is critical to the effectiveness of the firewall. You can choose between the following options:

  • Access rights of unknown IP addresses: Access attempts by other computers on the network are identified by the IP address and, in principle, are blocked by default. If you want to carry out a data exchange, you can allow it manually or add the IP address as an exception so that the next time access is allowed without consulting it first.
  • Check online program access - When installing programs that are available online, manual commit should also be configured. This way, you can be sure that you are installing the desired file and immediately recognize if an untrustworthy website tries to infect your computer with malicious software.
  • Visibility in networks: you can configure the visibility of your team in specific networks. It is recommended to hide the equipment in public networks (such as WiFi access points in airports or coffee shops) to protect it from unauthorized access attempts. Although visibility cannot be equated with granting access permission, it does make it more difficult for offenders when they try to access your data.
  • Active website content blocking: Some technologies for displaying dynamic content on websites (videos or graphic animations), such as Microsoft ActiveX or Adobe Flash applications, are always misused to spread malware because the content runs locally on the user's computer. The execution of that content can be blocked from the beginning.

These are just some of the parameters that you can configure in your firewall settings. Of course, in addition to blocking websites, services and IP addresses, you can also classify them as trustworthy and thus allow automatic access. Likewise, to recognize the limits of a firewall and that it can repel malware efficiently, it is necessary to adequately assess the accesses of programs and other computers.

For this reason, it is important that you do not only have the firewall, but at the same time use an antivirus program that compares both installed programs and dynamic website content with current virus definitions and blocks them or generates a warning before execution.

Many firewalls also work with ports. For an Internet data packet to reach your computer, it must pass this input filter. Each application uses a specific port. A firewall can be configured so that only the necessary ports can be opened . The firewall blocks all other accesses and thus prevents applications from receiving unwanted or unplanned data packets. Generally, this process is responsible for some programs not working due to the firewall. In this case, you should not disable the firewall , but simply open the necessary port.

What types of firewalls are there?

As noted previously, there are two different types of firewalls: the personal firewall (internal or desktop firewall) and the external firewall (hardware or network firewall).

The personal firewall is installed directly on the computer and is usually part of the operating system. Monitors data traffic and prevents unauthorized access to and from a PC's network services. Since much of the malicious software is accessed through security flaws in network services, most attempted attacks can be successfully blocked. The disadvantage of the firewall is that it actually reports that there is malware in the system architecture when it has already infected the PC. However, even if a clandestinely activated service needs to be uninstalled immediately, the firewall can at least prevent that service from continuing to spread malware freely across the network.

The external firewall stands between the home network and another network (for example, the Internet) and monitors all external access. In this case, it is not the computer that is connected to the Internet, but the firewall, which is subsequently networked with one or more computers. This corresponds to the typical structure of a LAN network, on whose router the external firewall is installed. It scans incoming traffic before it can reach the requesting computer, thus defending it against malware attacks before they have a chance to damage the computer.


If you are forced to purchase an external firewall, you can benefit from a similar level of security by taking a little detour. IONOS virtual servers, like all servers in the IONOS cloud infrastructure, are protected by a high-performance hardware firewall.

How do you activate a firewall?

If your operating system includes a serial firewall (as in Windows and iOS), it will already be activated when you start your computer for the first time . If you have to deactivate it, you will receive the corresponding system information. Then you can activate it yourself from the security settings of your operating system . There you will also find all the configuration options to adapt the firewall to your needs.