macOS is inherently secure, but whenever your computer connects to a network—especially public Wi-Fi in cafes or airports—it is exposed to potential incoming connections from other devices on that network. A firewall acts as a digital barrier, silently blocking unauthorised applications and services from accessing your Mac.
Surprisingly, Apple leaves the macOS firewall disabled by default on fresh installations. While the built-in router on your home network provides excellent protection, enabling the internal macOS firewall is a critical security step for laptops that frequently travel.
How to Enable the macOS Firewall
Turning on the firewall takes only a few seconds through the System Settings menu.
- Click the Apple Logo in the top-left corner of your screen.
- Select System Settings (or System Preferences on older versions of macOS).
- Scroll down the left-hand sidebar and click on Network.
- Click on Firewall in the main panel.
- Toggle the switch next to Firewall to the ON position.
Once enabled, the firewall immediately begins blocking all unauthorised incoming connections. This will not affect your ability to browse the web, check email, or stream video, as those are outgoing connections initiated by your Mac.
Configuring Firewall Options
In most scenarios, simply turning the firewall on is enough. However, if you regularly use file sharing, screen sharing, or host local web servers, you may need to configure specific exceptions.
- On the same Firewall settings screen, click the Options button.
- A list will appear showing all applications currently allowed to receive incoming connections. macOS usually populates this list automatically when an application requests access.
- To manually add an application to the allowed list, click the + (plus) button, navigate to your Applications folder, select the app, and click Open.
- To block an application that is currently allowed, select it in the list and click the – (minus) button.
Stealth Mode
For maximum security on public networks, you can enable “Stealth Mode.”
Within the Firewall Options menu, you will see a toggle switch for Enable Stealth Mode. When this is active, your Mac becomes completely invisible to automated network scanners (such as ping requests). Your computer will simply refuse to acknowledge that it exists on the network to anyone probing for vulnerabilities.
This is highly recommended for users who frequently work from coffee shops, hotels, or other untrusted public networks.