Monitor Network Connections in Mac OS X for Free with Private Eye
Private Eye is a free real-time network monitor app for Mac OS X 10.7+ that is extremely easy to use. Launching the app, you’ll start to see all open network connections, and you can then filter connections by app, monitor all open connections, or watch only incoming or outgoing transfer.
Connections are reported by application, the time of the connection, and arguably the most useful, the IP address that is being connected to by the app. If you have any interest in networking, security, or you just want to keep an eye on what apps are connecting to the internet and to where, you should download this app.