hello rennybosch, from the troubleshooting information you've submitted there's certainly nothing malicious going on in your firefox profile, you could update your plugins though...

can you specify how you are measuring the network traffic generated by firefox exactly?

for some general information on connections that firefox will initiate without your direct action also see How to stop Firefox from making automatic connections.

I downloaded a little app called Network Activity Indicator, which puts a little icon in the Taskbar. The icon blinks when there is network traffic.

If FF is open on a blank page or a page with very few links the indicator may blink for a few seconds but then stops. If FF is open on a busy page like Google News, the indicator blinks for 5-10 minutes before subsiding. That was what made me think there was a lot of prefetching going on.

Does the throbber on the Tab bar stop spinning to indicate that the page has finished loading?

I've noticed that the places.last_vacuum shows a rather old date from 19 Feb 2011 and there are also some prefs that are no longer used.

• places.last_vacuum: 1298076542

Maybe you should consider to reset the prefs or create a new profile (reset Firefox) to start with a fresh profile.

ok, i can reproduce your observation - however when i use the tcpview tool from http://technet.microsoft.com/en-us/sysinternals/bb897437 it is apparent that the only steady tcp packets sent are between two local ports (this means they won't leave your computer), which is apparently necessary for the functioning of firefox on non-unix systems. the background is explained here for example: http://superuser.com/questions/71340/firefox-is-listening-for-incoming-connections-on-two-ports-why

you can right-click the network indicator icon in the taskbar, go to settings & select "indicate selected interface traffic" & then choose the network interface which connects you to the internet. then the blinking will really represent incoming/outgoing traffic that is actually coming from the internet.

The spinner does stop after a short while, but the blinker goes on and on and on . . .

If the throbber starts working again then this usually means that some JavaScript is getting active on that page.

You can try to use the Web Console (Firefox/Tools > Web Developer;Ctrl+Shift+K) to see if new files are requested.

• https://developer.mozilla.org/en/Tools/Web_Console

You can also try the Live Http Headers extension to check for pages that are requested and other data.

• Live Http Headers: https://addons.mozilla.org/firefox/addon/live-http-headers/

Thanks Philipp, that's extremely helpful information. I changed the Setting in the activity indicator to Network traffic only, and the symptom has dramatically decreased. This completely alleviates my original concern. Problem solved.

Renny