Cyber Essentials: Firewalls
The Cyber Essentials Firewalls control covers the security boundary between your devices and the internet. A correctly configured firewall blocks unsolicited incoming connections before they can reach your devices or network. These guides walk you through every Firewalls requirement for home users.
Last reviewed: July 2026
Cyber Nova AI helps you prepare for Cyber Essentials. It doesn't award or certify it. Follow the steps here to get ready, then apply for certification through an accredited Cyber Essentials body when you're set.
What this control covers
- ✓Change your router's default admin password
- ✓Enable your router's built-in firewall
- ✓Enable Windows Defender Firewall on all Windows devices
- ✓Review and close unnecessary open ports on your business router
Firewalls Guides (7)
- Review firewall rules on your business routerCheck that only necessary ports are open on your business network router. Close any ports that are not required.
- Enable Windows Defender FirewallMake sure Windows Defender Firewall is turned on for both private and public networks on your Windows computer.
- Enable your router's built-in firewallMost routers include a built-in firewall that filters incoming traffic. Check that it is switched on.
- Change your router's default passwordYour router comes with a factory default password that is easy for attackers to guess. Change it to a strong, unique password.
- Set up a guest Wi-Fi network at homeCreate a separate Wi-Fi network for visitors and smart home devices. A guest network isolates your main computers and phones from anything you do not fully control or trust.
- Be careful what you do on public Wi-Fi on your phoneAvoid accessing banking apps, email, or any account that contains sensitive information when connected to public Wi-Fi. Public networks in cafés, hotels, and airports are not secure.
- Turn on your Linux firewallSwitch on the firewall that comes with your system so unwanted incoming connections are blocked by default.
Test yourself
A few quick questions to check what you have learned. Pick an answer to see whether it is right and why. Nothing is saved or scored.
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Start your free security checkCommon questions
What is a firewall?
A firewall is a security barrier that controls what network traffic is allowed to enter and leave a device or network. For home users and small businesses, the most important firewall is the one built into your internet router, which blocks unsolicited connections from the internet before they reach your devices. Cyber Essentials distinguishes the boundary firewall (your router, which protects your whole network) from a software firewall (built into each device, which matters most on untrusted networks like public Wi-Fi).
How do I check my firewall is switched on?
Two firewalls matter for most people. Your router's firewall is usually on by default, so sign in to your router's settings page to confirm it's enabled. On a Windows laptop, open Settings, search 'firewall', and check Windows Defender Firewall is on, especially before using public Wi-Fi.
Does my home router have a firewall built in?
Almost certainly, yes. Most consumer routers include a firewall by default. The key requirement under Cyber Essentials is that it is switched on and not left on factory-default settings, which may have unnecessary ports open or services enabled.
What does Cyber Essentials require for firewalls?
Cyber Essentials requires that all devices connecting to the internet do so through a properly configured firewall. For most home users and small businesses, this means checking that your router's built-in firewall is active, that unnecessary services are turned off, and that the admin password has been changed from the default.
Do I need a separate firewall if I have antivirus software?
They serve different purposes. Your router firewall blocks unsolicited connections from the internet. Antivirus protects against threats that arrive via normal browsing, email, or downloads. Windows also includes a software firewall (Windows Defender Firewall) that adds protection when you are on unfamiliar networks. You need both; they complement rather than replace each other.