Sniffnet

Sniffnet captures traffic on a network adapter you choose and presents it as statistics, real-time charts and a list of connections and hosts. Filters narrow the view, and captures can be exported or imported as PCAP files.

It is easier to approach than a full protocol analyser while still useful for spotting unexpected connections. Separate Intel and Apple silicon disk images are published on GitHub; capturing traffic may require the dependencies the project documents for each platform.