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title: Disable Outbound Firefox Connections | abcdesktop.io description: Configure Firefox policies to disable telemetry, Normandy, and other background network connections in an abcdesktop.io Remote Browser Isolation deployment. keywords: Firefox, disable connections, policies, telemetry, Normandy, RBI, remote browser isolation, abcdesktop, privacy tags: - FAQ - Firefox - RBI - security - privacy - firefox

How to Disable Mozilla Firefox Automatic Connections at Startup

Usage of policies.json

You can specify Firefox policies in a file called policies.json. You may need to create this file, as it is not present by default.

Path to policies.json depending on your OS (you may need to create intermediate directories):

  • Windows: C:\Program Files\Mozilla Firefox\distribution\policies.json
  • Linux: /usr/lib/firefox/distribution/policies.json
  • macOS: /Applications/Firefox.app/Contents/Resources/distribution/policies.json

You can find all policy templates for your Firefox version on the Mozilla GitHub page: https://github.com/mozilla/policy-templates/releases

Usage of autoconfig.js and firefox.cfg

Some preferences cannot be set through the policies.json file — for example, disabling Normandy — due to Firefox restrictions. These can instead be configured by creating a JavaScript file called autoconfig.js and a configuration file called firefox.cfg.

autoconfig.js is responsible for loading and executing firefox.cfg at startup.

autoconfig.js

// Setup config file
pref("general.config.filename", "firefox.cfg");
pref("general.config.obscure_value", 0);

Path to autoconfig.js depending on your OS (you may need to create intermediate directories):

  • Windows: C:\Program Files\Mozilla Firefox\defaults\pref\autoconfig.js
  • Linux: /usr/lib/firefox/defaults/pref/autoconfig.js
  • macOS: /Applications/Firefox.app/Contents/Resources/defaults/pref/autoconfig.js

Locked preferences are specified in the firefox.cfg file. Path to firefox.cfg depending on your OS:

  • Windows: C:\Program Files\Mozilla Firefox\firefox.cfg
  • Linux: /usr/lib/firefox/firefox.cfg
  • macOS: /Applications/Firefox.app/Contents/Resources/firefox.cfg

Usage of proxy.pac file

Despite all efforts to disable automatic connections via policies.json and firefox.cfg, a small number of connections may remain that cannot be disabled through policy settings alone. To work around this behavior, create a file named proxy.pac that blocks access to the remaining URLs by redirecting them to an unreachable proxy.

Save proxy.pac to your machine and note the file path.

Once saved, add the following line to the Proxy policy inside your policies.json file: "AutoConfigURL": "file:///path/to/your/proxy.pac"

Disable Startup Connections

policies.json

URL Parameter(s) to set
https://location.services.mozilla.com "browser.region.network.url": ""
https://contile.services.mozilla.com
https://tiles-cdn.prod.ads.prod.webservices.mozgcp.net		 "browser.topsites.contile.enabled": false
"browser.topsites.contile.endpoint": ""
https://spocs.getpocket.com "browser.newtabpage.activity-stream.discoverystream.enabled": false
https://push.services.mozilla.com "dom.push.connection.enabled": false
https://accounts.firefox.com "browser.startup.homepage_override.mstone": "ignore"
(also disables the news page)
https://shavar.services.mozilla.com "browser.safebrowsing.provider.mozilla.gethashURL": ""
"browser.safebrowsing.provider.mozilla.updateURL": ""
https://tracking-protection.cdn.mozilla.net "browser.safebrowsing.downloads.remote.enabled": false
http://detectportal.firefox.com "network.captive-portal-service.enabled": false
"network.connectivity-service.enabled": false
https://incoming.telemetry.mozilla.org
https://www.mozilla.org		 Set "DisableTelemetry" policy to true

firefox.cfg

URL Parameter(s) to set
https://normandy.cdn.mozilla.net
https://classify-client.services.mozilla.com		 lockPref("app.normandy.enabled", false)
lockPref("app.normandy.api_url", "")

Example of policies.json file

"policies": {
    "DisableTelemetry": true,
    "Preferences": {
        "browser.region.network.url": "",
        "browser.topsites.contile.endpoint": "",
        "browser.newtabpage.activity-stream.discoverystream.enabled": false,
        "browser.startup.homepage_override.mstone": "ignore",
        "browser.safebrowsing.provider.mozilla.gethashURL": "",
        "browser.safebrowsing.provider.mozilla.updateURL": "",
        "browser.safebrowsing.downloads.remote.enabled": false,
        "dom.push.connection.enabled": false,
        "network.captive-portal-service.enabled": false,
        "network.connectivity-service.enabled": false
    },
    "Proxy": {
        "Mode": "autoConfig",
        "AutoConfigURL": "file:///path/to/your/proxy.pac"
    }
}

Example of firefox.cfg file

// Disable Normandy service
lockPref("app.normandy.enabled", false);
lockPref("app.normandy.api_url", "");

Example of proxy.pac file

// File PAC
//
function FindProxyForURL(url, host)
{
  // just define hostname and unreachable port
  var var_blackhole = "127.0.0.1:12345"; // could be any other UNUSED port than 12345

  //URL deny definition - Blackhole for blocked URL

  if ( host == "firefox.settings.services.mozilla.com"
    || host == "content-signature-2.cdn.mozilla.net"
    || host == "firefox-settings-attachments.cdn.mozilla.net"
  ) {
    return "PROXY " + var_blackhole;
  }

  return  "DIRECT; ";
}

Sources