Stop Firefox from making connections by itself

I don’t know when it started exactly. But I think Firefox 60+ is affected by this.

Many months ago I wanted to set up a new Firefox (WebEx) for long term use. After install I did not permanently allow Firefox “as Webbrowser” in my Firewall, just in case I forgot to disable some privacy invading feature. Obviously the fresh install created lots of popups.

I then went ahead and started disabling everything related in options and about:config. This reduced firewall popups, but there would still be a popup - at startup, and every now and then when left idle in background.
I spend days searching the web for solutions, implemented the most restrictive user.js I could find. Made any changes I could imagine to be remotely related. Finally frustrated and desperate I ended up going delete-crazy on about:config, probably breaking the browser itself.
Yet, the firewall would still report Firefox making outbound connections, while idle with blank page.

I gave up, reinstalled. Since then I have a Firefox install for which I have to allow every single connection it wants to make. It is pretty damn annoying. And because of the multiple IPs necessary for some websites, I can never be sure. I might occasionally allow one of those connections not initiated by me by accident.

I wonder if any of you can replicate this issue; know how to solve it.

this might help you



yep you are right ; its roughly FF v60+ that often does that. I liike testing out web browsers with WireShark or tcpdump when I first try them out and one day I decided testing out older FF versions as well. If I remember right I think its v59+ that you need just to be able to view youtube lols.

If you are running v60-ish I think if you change all of the config settings - then that issue might go away.

Alsooo its great to keep in mind that I notice FF background tabs (such as tutanota) making connections automatically - I think in that case it’s just tutanota checking to see if there is new mail.

But ya… if you are seeing connections without any web browser tabs open, then its def a good idea to make sure you didn’t miss any about:config settings or try a diff FF version (they don’t ALL do that), or… a new browser :smiley:

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First of all, i’m not sure if i get what you mean correctly :joy: but if i’m right, all browsers do that “phoning home”. anyway, here are some tips might help ya!

or just set network.captive-portal-service.enabled to false (according to

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Thanks for trying to help. I wish I could edit the original post, to rephrase/clarify what I wrote.

I’ve now repeated the procedure with FirefoxESR78.
At first the result was the same.
Even after following all the guides, Firefox was still trying to connect somewhere.
I wrote down more than 20 different IPs. They are all owned by Amazon, or Amazon Cloudfront.

Then I did something new. I used mitmproxy to expose the URL Firefox is connecting to.

Mozillas guide already mentions the need to put “” into your host file. Because this is intentionally hardcoded into Firefox.
But it does not mention, it is also necessary to put “” into the hosts file.

Supposedly this “is used to update the list of trackers that are getting blocked when tracking protection is turned on.” (quote from a user over at mozilla support)
But even with tracking protection turned off, Firefox was still trying to connect. Hence the need to put it into the host file.

I saw, but did not further investigate, mentions of settings in about:config, which keep resetting themselves, no matter what you do. So that might be related.

Ok, so I finally managed to disable and block all hidden communications. Though I had to change so many things, I’ve lost track. This is not a browser I could feel safe and “in control” of.

Thanks for posting this :smiley: I’ve always just used Wireshark & tcpdump but I guess mitmproxy is a lot easier on the eyes .

I am def blocking these in case I use FF again one day :smiley: