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Does Your Mac Really Need a Firewall? What You Need to Know

Chances are that your computer is behind the firewall that’s part of your router, so having macOS’s firewall turned off makes it easier to set up connections with other Apple devices. But if you use a laptop and hop onto untrusted networks frequently, you should enable the firewall.

macOS also includes an assortment of shared network services to remotely access your content. If you keep those services enabled or use third-party apps, that could make your Mac vulnerable to a network attack. We’ll show you how to configure your firewall and when you need to use it.

The importance of a firewall as a part of a security strategy cannot be underestimated. We have already discussed in detail why you should use a firewall

You’ve heard of firewalls, but what are they really for? Do they stop viruses? Can you manage without one? We look at five reasons to install and use a firewall on your computer.

This component of the firewall will allow or deny access for an app to establish communication over the network. It is not based on the ports used. The built-in macOS firewall offers this, and by design, it’s simple and intuitive. You can specify, for each app, whether to allow or block incoming connections.

To turn on the firewall on your Mac, open System Preferences → Security & Privacy → Firewall. Click the lock icon in the lower-left of the window, enter your administrator password, and click Unlock.

If the window doesn’t already say Firewall: On, click the Turn On Firewall button. The green circle lights up, and your Mac will only allow incoming traffic for established connections, signed software, and enabled services. You can later turn off your Mac’s firewall using the corresponding button.

This component of the firewall is embedded deep in the operating system kernel. PF is the OpenBSD packet filter. Its primary function is to filter network packets by matching the properties of individual packets (and the network connections built from them) against the filtering criteria defined in the ruleset.

With a PF firewall, you can control network traffic based on virtually any packet or connection type. This includes source and destination address, interface, protocols, and ports. Based on these criteria, you can let the packet pass, block it, and trigger events that other parts of the operating system can handle.

A PF firewall came into effect on macOS starting with Mac OS X 10.7 Lion. While ALF is easy and intuitive to use, setting up a PF firewall requires a thorough knowledge of syntax, logic, and network configuration. You must edit the configuration files manually, and the packet filter monitoring is entirely done from the command line.

macOS includes many built-in services to share files, printers, access resources remotely, and more. To enable a service, navigate to System Preferences → Sharing and tick the box next to each service you want to use.

Since the firewall works on the per-application basis, you’ll see these services listed by name rather than a port number. For example, you’ll see File Sharing on the pane instead of port 548.

To customize the firewall, head back to the Firewall panel and click the Firewall Options button. This will reveal more firewall configurations. Use the Plus and Minus buttons to add or remove apps as needed. You can also choose to check some additional options below.

Any services you’ve checked in the Sharing panel as above will automatically appear in the list of allowed connections. But if you disable any of the services, they’ll no longer appear in the firewall options pane.

When any third-party app starts listening for incoming connections, you’ll see a message asking “Do you want the application “” to accept incoming network connections?” Click Allow or Deny to modify the firewall settings. Apps you allow access will appear on the list.

The built-in firewall gives you the ability to monitor and block incoming connections. However, you can monitor outgoing connections as well. How can an average user utilize outgoing traffic data? Let’s illustrate with some examples.

Most apps that you use on your Mac have a visible interface and continuously exchange data between your machine and servers located elsewhere. But many processes running in the background also send and receive data.

Take a look at all the processes in the Activity Monitor → Network tab. How can you be sure that all those connections are genuine?

Apps partake in activities all the time: your email app downloads new messages, apps periodically check for updates, and Dropbox syncs newly changed files. These activities are fine, but if you download a malicious app that secretly logs your keystroke and sends sensitive data to a malicious actor, that’s a problem.

Premium apps routinely “phone home” to check your license data, but some developers…

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