You lock your house door at night right? You don’t let random people walk in. Delivery guy comes, you check first. Stranger knocks, you look through window before opening.
Makes sense.
Firewall does same thing. But for your computer.
Why do we even need this
Your laptop is connected to internet. Which means technically, other computers can try to reach yours.
Most are fine. Google, YouTube, Netflix.
But some are not. There are people who scan thousands of computers looking for open doors. If they find one, they get in. Steal data, install virus, use your computer to attack others.
I’m not making this up. Run a server on internet for one day without protection. You’ll see hundreds of random connection attempts from IPs you never heard of. It’s crazy.
So we needed something that sits at the door and checks everyone.
What firewall does
Every time data comes to your computer or goes out, firewall checks it.
It’s like a watchman with a list.
“Google wants to send you data? Ok, allowed.”
“Some random IP from Russia trying to connect? No. Blocked.”
“Chrome wants to access internet? Fine.”
“Some unknown app trying to send your files somewhere? Nope, not happening.”
Simple checking. But very powerful.
Let me give you real example
At my work we have servers. Real users connect to it everyday.
We set firewall rules:
- Allow website traffic (so users can use the app)
- Allow our office IP to connect for maintenance
- Block everything else
That’s it. Three rules.
Now someone in random country tries to hack in? Firewall blocks. They don’t even get response. For them, our server doesn’t exist.
We checked logs once. Thousands of blocked attempts in single week. All from IPs we don’t know, trying random stuff. Firewall stopped all of them silently.
Without firewall? Maybe one of those attempts would have worked.
Two places firewall can be
On your router
Your wifi router at home? It has basic firewall. It protects all devices connected to your wifi. Phone, laptop, smart TV, everything.
Companies have bigger dedicated firewall devices. More powerful, more rules, more protection.
On your computer
Windows has firewall built in. Mac has one too. Linux also.
This protects your specific computer. Even if you connect to some random cafe wifi which might not be secure, your computer’s firewall still protects you.
Best is to have both. Router firewall + computer firewall. Two layers.
How it fits in your network
Simple picture:
Internet → Your Router (firewall here) → Your devices
Data comes from internet. Hits router first. Router’s firewall checks. Only allowed stuff passes through to your laptop/phone.
For companies it’s similar but bigger:
Internet → Big Firewall Device → Company network → Employee computers
Common question: “I have antivirus, why need firewall?”
Different jobs bro.
Antivirus catches bad stuff after it reaches your computer.
Firewall stops suspicious stuff from reaching your computer in first place.
It’s like saying “I have doctor so why lock door?”. Doctor helps when you’re sick. Door lock prevents strangers from entering. You need both.
One thing many people don’t know
Firewall works both ways. It checks incoming AND outgoing.
Why outgoing matters?
Say some malware somehow got into your system. Now it wants to send your passwords to hacker’s server.
Good firewall catches this. “Wait, this app is trying to send data to unknown server. Blocked.”
So even if something bad gets in, firewall can stop it from sending your data out. Last line of defense.
How to check yours is on
Windows: Search “Firewall” in start menu. Click “Windows Defender Firewall”. Make sure it says ON.
Mac: System Preferences → Security & Privacy → Firewall tab → Check if enabled.
Takes 10 seconds to verify. Do it now if you haven’t.
The point
Internet is not safe place. Lots of good stuff but also lots of bad actors scanning for easy targets.
Firewall is your first protection. It sits at the door, checks every packet, blocks suspicious ones.
Not fancy. Not exciting. But when your system stays safe while others get hacked - firewall did its job.
Security is not one thing. It’s layers. Firewall is first layer. The watchman who never sleeps.
