A very useful command line tool which ships with Windows is Netstat. Netstat allows you to view all active network connections on your computer. This is a great way to make sure you don’t have anything unexpected on your computer sending or receiving network traffic.

An alternate, more user friendly, version of Netstat is TCPView. From the web site’s description:

TCPView is a Windows program that will show you detailed listings of all TCP and UDP endpoints on your system, including the local and remote addresses and state of TCP connections. [...] TCPView provides a more informative and conveniently presented subset of the Netstat program that ships with Windows.

After using TCPView, I have noticed several improvements over using Netstat such as realtime refreshes with new entries highlighted, sortable results and the ability to pause displays.