I am a great fan of SysInternals Suite since before they sold to Microsoft. I have been using TCPView since 2001 (or so)(just mentioning in case anyone who doesn't know the tools can find them useful). I also use Windows Firewall Control (WFC) a neat and cheap software that makes the Windows firewall management very easy. I know that FF on "idling" more has 4-5 open connections mainly to cloudfront, aws, akamai. Unfortunately FF prefers these CDN hosts over the true targets so I can't know more (and too lazy to use wireshark to find out).