A firewall, in Spanish “firewall”, is a computer security system that you can use to protect your network or devices from unauthorized access and cyber threats.
It is a term whose origin dates back to the 1980s, when the use of the Internet began to become popular. Researchers Bill Cheswick and Steve Bellovin, belonging to the AT&T Bell laboratory, were the pioneers in the creation and implementation of the first firewalls to defend networks from possible intruders.
How a firewall works
A firewall provides a protective barrier for software and hardware that determines which data is truly secure, allowing access, and which has to be blocked to protect the network. It works as follows:
-Traffic monitoring. First, the firewall continuously scans all data traffic trying to enter or leave your network or devices. That is, it controls data packets, which are divided into small segments of information and moved over the Internet.
In this sense, the firewall reviews each of the packets to ensure that they do not pose a threat.
-Data filtering. The firewall filters all data packets using a series of rules that you can establish depending on your needs.
For example, you have the ability to filter data by IP address to block or allow access to a particular address. You can also block ports – specific points on the device where traffic passes – and prevent unwanted applications or services from connecting to your network.
Additionally, you can filter using a protocol. That is, you determine a series of rules about the way in which all the data will be transmitted. In this way, the firewall can block or allow certain protocols, such as HTTP, FTP or SSH, depending on their use on the network as such.
-Blocking or granting of permission. When all packets are filtered, the firewall decides whether to allow the traffic or block it, based on whether the packet actually meets the configured security rules.
That is, in case you want to enter a web portal that you placed on a blacklist, logically the firewall will deny the connection, either silently or by sending you an error notification.
However, if that packet comes from a secure site and does not contain data that could be suspicious, the firewall allows it and lets it pass without problems.
-State inspection. It is a technique that most modern firewalls use to monitor all active connections. This means that the firewall will not only analyze your data packets individually, but it will also completely analyze your communication session.
For example, if some traffic is part of a legitimate activity, you will allow it. On the other hand, if it notices unusual behavior, it immediately blocks it, helping you identify connections that may seem very safe at first, but could actually be malicious.
Keep in mind that some firewalls have the peculiarity that they store a log of all the traffic they filter over time. Thus, if you are an administrator of one you have the possibility of knowing what data it has blocked or allowed, which is quite useful especially if you are trying to discover an attack, problem on your network or simply want to know a little more detail How your network is working.
How to install a firewall
In order for you to install a firewall you have to do the following steps:
-Choose a type of firewall. You can choose a free firewall or one that is paid. For example, software firewalls come pre-installed on operating systems such as Windows or macOS and typically do not incur any additional costs.
However, if you want a more robust system, it is recommended that you buy one through a cybersecurity company.
-Installation process. If your intention is to protect your computer, you simply have to activate the firewall of your operating system. Go to the security settings section and look for the firewall option. Enable it if it is not.
If you opt for a third-party firewall, download and install it. In these cases, the manufacturer may offer you support and guides so that you can correctly adjust all filtering rules according to your requirements.
Now, if you want the firewall to shield your entire network, you can do it at the level of your Wi-Fi router. Many routers already come with this function included. You just have to access the router configuration from a web browser by entering the IP address of your device, the username and the password. Normally this information is attached to the router label or by consulting the user manual.
When you manage to enter the administrator you must find a “security” or “firewall” option and proceed to enable it. At this point, it should offer you more settings that allow you to establish the rules and thus control the traffic between your internal and external network.
If you opt for a paid firewall to use on your router, you will most likely have to make more advanced settings, which may include network segmentation, content filtering, and access to certain apps.
As a suggestion, whatever type of firewall you are going to install, seek technical assistance to ensure a correct configuration according to your needs.