How to configure and use the built-in firewall of the Radiant Shield app and network connection monitoring in macOS?

Network security in macOS is provided by a built-in firewall that helps protect your computer from unauthorized access from the local network and the Internet by controlling incoming network connections to system and third-party applications.

To enable and perform basic configuration of the built-in firewall, open the System Settings of your Mac. Go to the Security & Privacy or Privacy & Security section depending on the operating system version, and then find the Firewall subsection and switch the main toggle to the active position.

To fine-tune rules for specific programs, click the Options button next to the firewall toggle. In the window that appears, you can add or remove applications using the plus and minus buttons, as well as manually allow or block incoming network connections for each individual utility.

For more advanced control of network activity and real-time connection diagnostics, the native Activity Monitor utility is used. Launch it via Spotlight, go to the Network tab, where you can see the amount of sent and received data for each running process, as well as identify suspicious network activity.

If you require deep analysis of network packets, macOS comes with a pre-installed powerful command-line tool tcpdump. Open Terminal and enter the command sudo tcpdump -i en0 to capture and display all packets passing through your primary network interface, which is especially useful when debugging network applications and web services.