What Is a Firewall and Do You Actually Need One?
A firewall is one of the most important security tools on your computer — and one of the least understood. Here is a plain English explanation of what it does and why it matters.
What a firewall actually does
A firewall monitors all network traffic going in and out of your computer and blocks anything that does not match its rules. Think of it as a security guard at the door — it checks every connection request and decides whether to let it through. It stops unauthorised programmes from communicating over the internet and blocks certain types of incoming attack.
Software firewall versus hardware firewall
Your computer has a software firewall built into the operating system — Windows Firewall on Windows and the Firewall option in System Settings on Mac. Your router also contains a hardware firewall that protects your entire home network. Both work together. The software firewall protects the individual computer; the router firewall protects the whole network.
Is Windows Firewall good enough?
For most home users, Windows Defender Firewall is perfectly adequate. It is well-designed, maintained by Microsoft, and works silently in the background. The main reason people turn to third-party firewalls is for more granular control over which applications can access the internet — useful for privacy-conscious users but unnecessary for most people.
How to check if your firewall is enabled
On Windows 10 and 11: go to Settings > Privacy and Security > Windows Security > Firewall and Network Protection. It should show Domain, Private, and Public network with green ticks. On Mac: go to System Settings > Network > Firewall. Enable it if it is off. Cerebro Scan shows your firewall status directly on the Security tab.
What a firewall cannot do
A firewall is not a substitute for antivirus software. It controls network connections but cannot detect malware that is already on your computer. It does not protect you from phishing attacks or malicious websites. Think of it as one layer of security among several — firewall, antivirus, strong passwords, and regular updates all work together.
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