Home Firewalls — Your Computer's Locked Front Door
Firewalls originated in the construction industry. Their purpose was to isolate one part of a building from another during a fire, thus limiting the damage. Automobiles also had firewalls installed between the engine and the occupants to reduce the potential impact of fires and heat, and added the advantage of reducing noise.
In the same manner, firewalls for computers were developed to isolate one group of computers from another. Originally, all computers were simply interconnected and each computer could talk to all of the others connected on a common network. This was fine until a computer virus was formed and spread from one computer to all of the computers on the network.
The result was that most of the computers shut down or became so clogged with virus generated traffic that they could not function. It was quickly decided that a device needed to be developed to isolate computers from each other. This led to the development of the computer firewall. While some argued that firewalls were not necessary, others knew that as the network grew, the lack of firewalls could have a strong negative impact on the network.
Today's computer firewalls have not changed much since they were first developed. They have a few more bells and whistles, but they still perform the same basic function: to keep computers apart.
They do this by limiting what connections can be made from the external side of the firewall (usually the internet side) to the inside of the firewall (the protected side). They operate in a manner similar to the receptionist who directs telephone calls to the designated party if the call is expected or to voicemail if the party is busy. Just as a boss gives a receptionist directions on which calls to allow and which ones to drop, computer firewalls have rule sets that define which connections are allowed and which ones are not.
Typically, a home router and/or Wi-Fi Access Point that comes from your service provider will have a firewall built in that segments your home network from the Internet. Additionally, modern operating systems will have software based firewalls built-in on the host. Always ensure that your host firewall is enabled to maximize your computer's security.
Start at the network connection
Before your Internet installation technician leaves, be sure to collect as much documentation as possible regarding the router's features. Ensure that you have Administrative access, and ensure that the firewall be configured correctly before he/she leaves.
Moving to the home computer
Most of this tutorial is directed at home users with Windows 10. If you are running an older version of Windows such as Windows 8, Windows 7, or below, you should upgrade your operating system. The newer operating systems offer better security support. If you are using MacOS, then you can enable the built in firewall from Security & Privacy in System Settings. MacOS's firewall is disabled by default and should be turned on.
For Windows 10, select the "Windows" button, open the "Settings", and type "Firewall" into the search bar at the top. Click on the "Windows Defender Firewall" icon. If the firewall is designated as off, click the "on" button. In order to allow an app or feature through the firewall, you may click on "Allow an app or feature through Windows Defender Firewall", however, for each opening you make in the firewall, you are allowing that service to be accessed from an outside computer. Should there be a weakness in that service, it could lead to a compromise.
If you are connecting to an unsecured, high speed wired or wireless network, such as one in Starbucks or a hotel room, then make sure you are using the Firewall profile associated with "Guest or public networks". This will provide the highest level of protection available but may impact certain network functions such as sharing files and printers.
If you still have questions, try using Microsoft's help at www.microsoft.com. It can quite often answer many questions. Additionally, your internet service provider can also help you to address many concerns.