How does a firewall actually work?

Transcript

So what is a firewall and how does it work? Welcome to yet another episode of my hit series, how the heck does that thing work? Where I teach you how the heck that thing works. A firewall is a set of rules and instructions that sits between your device and the internet, checking every bit of incoming and outgoing traffic against that set of rules. Those rules are based on things like which app is sending the request and which port it's trying to use. Every online service uses a specific port, kind of like a number door. A firewall can block a specific port entirely, which stops any traffic from using that door, whether it's good or bad. The firewall can also block traffic based on the source, refusing connections from specific addresses that might be known for suspicious activity. Windows and most routers come with a basic built in firewall that's already turned on and doing its thing by default. It's not as serious as blocking hackers in some dramatic sense. It's basically just filtering traffic against like a pretty boring rulebook over and over and over, really fast. Most of what it blocks is automated scanning traffic that's basically just like poking at random devices, looking for an open door. And you're not really gonna notice a firewall doing its job because it's supposed to be invisible when it's doing its job correctly. Think of it less like a wall and more like a really strict bouncer. And that bouncer is checking IDs at a door that nobody else can see. Did you already know this? Tell me what other topics you want me to explain next in the comments.

Transcribed automatically from the video, so small errors are possible.