Sunday, August 16, 2015

How to stop Firefox from making automatic connections


Some people are concerned about the connections Firefox makes to the Internet, especially when those connections are made for no apparent reason (see Mozilla's Firefox Browser Privacy Notice for additional information). This article explains various reasons why Firefox may make a connection to the Internet and how you can stop it from doing so, if you wish.

Automatic updates and Security

Auto-update checking

Warning: Disabling update checking is not recommended and will leave you open to security vulnerabilities that get fixed in newer versions.
Firefox occasionally checks to see if any updates are available for itself and for your search engines. To disable these checks:
  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.
    Click the menu button New Fx Menu and choose Options.Preferences.
  2. Select the Advanced panel.
  3. Select the Update tab.
  4. Check Never check for updates (not recommended: security risk) and uncheck Search Engines. Close the about:preferences page.
Firefox also checks to see if any updates are available for your add-ons (extensions, themes). To disable this check:
  1. At the top of the Firefox window, click on the Firefox buttonOn the menu bar, click on the Tools menuAt the top of the Firefox window, click on the Tools menu, and then click Add-ons. The Add-ons Manager tab will open. Click the menu button New Fx Menu and choose Add-ons. The Add-ons Manager tab will open.
  2. In the Add-ons Manager tab, select the Extensions panel.
  3. At the top of the tab, click the "Tools for all add-ons" Add-on Tools Icon menu, uncheck Update Add-ons Automatically and then select Reset All Add-ons to Update Automatically.

Blocklist updating

Warning: Disabling the blocklist is not recommended, as it may result in you using untrustworthy add-ons, revoked certificates or unstable graphics drivers.
Firefox may be updating its blocklist, which is used to block malicious extensions, vulnerable plugins, revoked certificates and graphics drivers known to cause crashes. For more information, see Blocklisting (MozillaWiki), Blocklisting/Graphics (MozillaWiki), the Revoking Intermediate Certificates: Introducing OneCRL blog post and the article Add-ons that cause stability or security issues are put on a blocklist. To disable this feature:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference extensions.blocklist.enabled.
  3. Observe the Value column of the extensions.blocklist.enabled row.
    • If it is set to false then do nothing.
    • If it is set to true, double-click on it to set it to false.

Anti-phishing list updating

Warning: Disabling the anti-phishing protection is not recommended, as it will leave you vulnerable to untrustworthy websites that might try to steal your financial information and/or your identity.
The phishing protection list may be updating itself. To turn this off:
  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.
    Click the menu button New Fx Menu and choose Options.Preferences.
  2. Select the Security panel.
  3. Uncheck Block reported web forgeries.

Anti-malware list updating

Warning: Disabling the anti-malware protection is not recommended, as it will leave you vulnerable to malicious file downloads or untrustworthy websites that might try to infect you with a virus, trojan or spyware.
The malware protection list may be updating itself. To turn this off:
  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.
    Click the menu button New Fx Menu and choose Options.Preferences.
  2. Select the Security panel.
  3. Uncheck Block reported attack sites.
In addition, when you download an application file, Firefox will verify its signature. If it is signed, Firefox then compares the signature with a list of known safe publishers. For files that are not identified by the lists as “safe” (allowed) or as “malware” (blocked), Firefox asks Google’s Safe Browsing service if the software is safe by sending it some of the download’s metadata. To turn off this part of malware protection:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference browser.safebrowsing.appRepURL.
  3. Double-click on it and set its value to a blank string.

Secure website certificates

When you visit a secure website (i.e. "https"), Firefox will validate the website's certificate. This may involve communicating with a third-party status provider specified by the certificate over a protocol namend OCSP to confirm that the certificate is still valid. To turn this off:
  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.
    Click the menu button New Fx Menu and choose Options.Preferences.
  2. Select the Advanced panel.
  3. Select the Certificates tab.
  4. Uncheck Query OCSP responder servers to confirm the current validity of certificates.

Prefetching

Firefox will prefetch certain links if any of the websites you are viewing uses the special prefetch-link tag. For more information, please see the Link Prefetching FAQ. To disable Link prefetching:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference network.prefetch-next.
  3. Observe the Value column of the network.prefetch-next row.
    • If it is set to false then do nothing.
    • If it is set to true, double-click on it to set it to false.

DNS prefetching

In order to reduce latency, Firefox will proactively perform domain name resolution on links that the user may choose to follow as well as URLs for items referenced by elements in a web page. For more information, please see the DNS Prefetching blog post. To disable DNS prefetching:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference network.dns.disablePrefetch.
  3. Observe the Value column of the network.dns.disablePrefetch row.
    • If it is set to true then do nothing.
    • If it is set to false, double-click on it to set it to true.

Speculative pre-connections

To improve the loading speed, Firefox will open predictive connections to sites when the user hovers their mouse over thumbnails on the New Tab Page or the user starts to search in the Search Bar, or in the search field on the Home or the New Tab Page. In case the user follows through with the action, the page can begin loading faster since some of the work was already started in advance. To disable this feature:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference network.http.speculative-parallel-limit.
  3. Observe the Value column of the network.http.speculative-parallel-limit row.
    • If it is set to 0 then do nothing.
    • If it is set to a different value, double-click on it to set it to 0.

Add-on list prefetching

Each time the Add-ons manager is opened, Firefox prefetches a list of add-ons to improve responsiveness of the Get Add-ons pane. This connection is not made if the add-ons manager is not opened.

User-invoked content

Home page loading

Your home page may be loading. To change your home page to something that doesn't generate connections to the Internet:
  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.
    Click the menu button New Fx Menu and choose Options.Preferences.
  2. Select the General panel.
  3. Either set When Firefox starts to Show a blank page or set it to Show my home page and click Restore to Default. Close the about:preferences page.

Extensions

An extension you have installed may be making a connection to a website that it relies on. For example, a connection to a website to synchronize your bookmarks, a connection to a website to update a list of sites to block, etc. Or it is possible an extension could be changing the expected behavior of Firefox in other ways. For example, FasterFox extension has an option to prefetch all links. To easily disable all of your extensions please read the Troubleshoot Firefox issues using Safe Mode article, paying particular attention to the Disable all add-ons option under the Make Changes and Restart section. To disable or remove your extensions, see the Disable or remove Add-ons article.
Firefox also checks to see if any updates are available for your add-ons (extensions, themes). To disable this check:
Warning: Disabling add-on update checking is not recommended and leaves you open to security vulnerabilities that get fixed in newer versions.
  1. At the top of the Firefox window, click on the Firefox buttonOn the menu bar, click on the Tools menuAt the top of the Firefox window, click on the Tools menu, and then click Add-ons. The Add-ons Manager tab will open. Click the menu button New Fx Menu and choose Add-ons. The Add-ons Manager tab will open.
  2. In the Add-ons Manager tab, select the Extensions panel.
  3. At the top of the tab, click the "Tools for all add-ons" Add-on Tools Icon menu, uncheck Update Add-ons Automatically and then select Reset All Add-ons to Update Automatically.

Live Bookmarks updating

Live Bookmarks automatically reload themselves on a regular basis, and in doing so will make a connection to the Internet. Deleting all your Live Bookmarks will stop these connections from being made.

Downloads restarted

When you start Firefox, any interrupted downloads from your previous browsing session may be automatically resumed.
  1. Press Ctrl + JCtrl + Shift + Ycommand + J to open the Downloads window.
  2. Ensure nothing is currently being downloaded.

Search plugin icon loading

When you add a custom search plugin that doesn't come with an included icon, Firefox might look up the icon at a remote address that is specified in the search plugin once and cache it for future use.

Firefox Sync

If you're using Firefox Sync, it will establish regular connections in order to synchronize your data to Mozilla's Sync servers and across your connected devices. In order to choose what data gets synchronized or to disconnect from Sync, see the How do I choose what types of information to sync on Firefox? article.

Firefox Hello

If you're using the Firefox Hello video and voice chat feature of the browser by signing in with a Firefox Account or starting a conversation, there will be a connection established in order to set up a call, once your conversation partner joins a conversation remotely. Besides signing out from Firefox Hello or deleting a conversation, you can also disable Firefox Hello:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference loop.enabled.
  3. Observe the Value column of the loop.enabled row.
    • If it is set to false then do nothing.
    • If it is set to true, double-click on it to set it to false.

Mozilla content

Tiles

When you open a new tab in Firefox, you see several tiles that link to different websites. For new users, the New Tab Page in Firefox provides recommendations including both referrals to sponsored partner sites and content we consider important to our mission ("Directory Tiles"). For existing users Firefox will display tiles based on a user’s browsing history, where for some partner sites the default screenshot might be replaced with a better image ("Enhanced Tiles"). Both Directory Tiles and Enhanced Tiles will establish a connection to download content and the thumbnails to be shown in the New Tab Page. In order to disable this behaviour, refer to About Tiles in New Tab.

Snippets

If you use the built-in default homepage about:home, Firefox will show some Mozilla related content around the search box ("Snippets"), which is updated once a day. If you'd like to disable connections to Mozilla's snippets server:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference browser.aboutHomeSnippets.updateUrl.
  3. Double-click on it and set its value to a blank string.

Geolocation for default search engine

In order to set the right default search engine for your location, Firefox will perform a geolocation lookup once by contacting Mozilla's servers and store the country-level result locally. This connection happens on the first start of Firefox - in case you want to prohibit that, you will have to preconfigure the browser and set the browser.search.geoip.url preference to a blank string.

"What's new" page

After a browser update, Firefox might show an additional tab next to your usual homepage to offer more information on changes or new features included in the update. To disable this page from being shown:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference browser.startup.homepage_override.mstone.
  3. Double-click on it and set its value to ignore.

Add-on metadata updating

The Add-ons manager displays information about each add-on you have installed and provides personalized recommendations in the Get Add-ons pane. To keep this data updated, Firefox will request information from the Mozilla Add-ons gallery once a day (for more information, see this blog post). To disable these updates:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference extensions.getAddons.cache.enabled.
  3. Observe the Value column of the extensions.getAddons.cache.enabled row.
    • If it is set to false then do nothing.
    • If it is set to true, double-click on it to set it to false.

Diagnostics

Firefox can submit certain diagnostics data including Telemetry, Firefox Health Report and Crash Reports data to Mozilla to provide information that helps improving the browser. In order to disable the sharing of this data, refer to Data Choices Tab.

Media capabilities

OpenH264 codec

Firefox will make use of the OpenH264 codec provided by Cisco in order to support the H.264 video codec in WebRTC, a technology allowing for peer-to-peer video communication on the web, like in Firefox Hello. For more information about this, see the OpenH264 Now in Firefox blog post. The OpenH264 codec is not distributed with Firefox but gets downloaded at the first start of Firefox. In case you want to prohibit that, you will have to preconfigure the browser and set the media.gmp-gmpopenh264.autoupdatemedia.gmp-gmpopenh264.enabled preference to false.

WebRTC

WebRTC (Web Real-Time Communication) is a technology which provides direct browser-to-browser communication (audio, video, filesharing). As it is drafted and implemented at the moment, WebRTC can lead to your local IP address being exposed to websites even when you are behind a VPN or a NAT router - in the WebRTC API this data would be used to set up a peer-to-peer connection between two clients. There is discussion about if and how this should be adressed at the moment. If you would like to disable WebRTC:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference media.peerconnection.enabled.
  3. Observe the Value column of the media.peerconnection.enabled row.
    • If it is set to false then do nothing.
    • If it is set to true, double-click on it to set it to false.

Send Video To Device

Firefox contains a "Send Video To Device" feature to send HTML5 video content to a Roku, Chromecast or similar device in the same network. In order to discover and pair with such a device, Firefox will send SSDP packages (Simple Service Discovery Protocol, multicast address 239.255.255.250, port 1900) to the local network which can trigger a firewall dialog asking you if you want to allow such connections. A setting to control this behaviour will be available in an upcoming version of Firefox.To disable this feature:
  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
  2. In the about:config page, search for the preference browser.casting.enabled.
  3. Observe the Value column of the browser.casting.enabled row.
    • If it is set to false then do nothing.
    • If it is set to true, double-click on it to set it to false.

Malware

If your computer is infected with a virus, trojan, spyware, or other malicious software, then Firefox's Internet connection may be being piggybacked in order for the malware to communicate with its author or to deliver advertisements, etc. If you suspect this is the case, consider seeking advice from a forum specializing in malware removal. For more information, see Troubleshoot Firefox issues caused by malware.

Loopback connection

Note: This does not apply to Linux systems.
A loopback connection (to IP address 127.0.0.1) can be made by Firefox on non-Unix machines. In this case the browser is communicating with itself as expected, and it is not recommended that this communication be blocked. See bug 100154 for more information.
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