Firefox/Privacy

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This article overviews how to configure Firefox to enhance security and privacy.

Configuration

The following are privacy-focused configuration tweaks to prevent browser fingerprinting and tracking.

Anti-fingerprinting

Mozilla has started an anti-fingerprinting project in Firefox, as part of a project to upstream features from Tor Browser. Many of these anti-fingerprinting features are enabled by setting about:config:

  • privacy.resistFingerprinting true

There is no user-facing documentation about this flag, and Mozilla does not recommend users enable it, since it will break a few websites (it exists mostly to make life easier for the Tor Browser developers). But it does automatically enable many of the features listed below (such as changing your reported timezone and user agent), as well as protection against other, lesser-known fingerprinting techniques. See the tracking bug that lists many of these features.

Tracking protection

Firefox gained an option for tracking protection. It can be enabled by setting about:config:

  • privacy.trackingprotection.enabled true

Apart from privacy benefits, enabling tracking protection may also reduce load time by 44%.

Note that this is not a replacement for ad blocking extensions such as uBlock Origin and it may or may not work with Firefox forks. If you are already running such an ad blocker with the correct lists, tracking protection might be redundant.

Change browser time zone

The time zone of your system can be used in browser fingerprinting. To set Firefox's time zone to UTC launch it as:

$ TZ=UTC firefox

Or, set a script to launch the above (for example, at /usr/local/bin/firefox).

Change user agent and platform

You can override Firefox's user agent with the general.useragent.override preference in about:config.

The value for the key is your browser's user agent. Select a known common one.

Tip:
  • The value Mozilla/5.0 (Windows NT 6.1; rv:52.0) Gecko/20100101 Firefox/52.0 is used as the user agent for the Tor browser, thus being very common.
  • The #Anti-fingerprinting option also enables the Tor browser user agent and changes your browser platform automatically.
Warning: Changing the user agent without changing to a corresponding platform will make your browser nearly unique.

To change the platform for firefox, add the following string key in about:config:

general.platform.override

Select a known common platform that corresponds with your user agent.

Tip: The value Win32 is used as the platform for the Tor browser, corresponding with the user agent provided above.

WebRTC exposes LAN IP address

To prevent websites from getting your local IP address via WebRTC's peer-to-peer (and JavaScript), open about:config and set:

  • media.peerconnection.ice.default_address_only to true
  • media.peerconnection.enabled to false. (only if you want to completely disable WebRTC)

You can use this WebRTC test page and WebRTC IP Leak VPN / Tor IP Test to confirm that your internal/external IP address is no longer leaked.

Disable telemetry

Set toolkit.telemetry.enabled to false and/or disable it under Preferences > Privacy & Security > Firefox Data Collection and Use.

Enable Do Not Track Header (DNT)

Note: The remote server may choose to not honour the Do Not Track request.
Warning: The Do Not Track header may be used to fingerprint your browser, since most users leave the option disabled.

Set privacy.donottrackheader.enabled to true or toggle it in Preferences > Privacy & Security > Tracking Protection

Disable/Enforce Trusted Recursive Resolver

Firefox 60 introduced a feature called Trusted Recursive Resolver (TRR). It circumvents DNS servers configured in your system, instead sending all DNS requests over HTTPS to Cloudflare servers. While this is significantly more secure (as "classic" DNS requests are sent in plain text over the network, and everyone along the way can snoop on these), this also makes all your DNS requests readable by Cloudflare, providing TRR servers.

  • If you trust DNS servers you've configured yourself more than Cloudflare's, you can disable TRR in about:config by setting network.trr.mode (integer, create it it it doesn't exist) to 5. (A value of 0 means disabled by default, and might be overridden by future updates - a value of 5 is disabled by choice and will not be overridden.)
  • If you trust Cloudflare DNS servers and would prefer extra privacy (thanks to encrypted DNS requests), you can enforce TRR by setting network.trr.mode to 3 (which completely disables classic DNS requests) or 2 (uses TRR by default, falls back to classic DNS requests if that fails). Keep in mind that if you're using any intranet websites or trying to access computers in your local networks by their hostnames, enabling TRR may break name resolving in such cases.
  • If you want to encrypt your DNS requests but not use Cloudflare servers, you can point to a new DNS over HTTPS server by setting network.trr.uri to your resolver URL. A list of currently available resolvers can be found here, along with other configuration options for TRR.

Disable geolocation

Set geo.enabled to false in about:config.

Disable Safe Browsing service

Safe Browsing offers phishing protection and malware checks, however it may send user information (e.g. URL, file hashes, etc.) to third parties like Google.

To disable the Safe Browsing service, in about:config set:

  • browser.safebrowsing.malware.enabled to false
  • browser.safebrowsing.phishing.enabled to false

In addition disable download checking, by setting browser.safebrowsing.downloads.enabled to false.

Disable WebGL

WebGL is a potential security risk.[1] Set webgl.disabled to true in about:config if you want to disable it.

Extensions

This section lists Firefox-only privacy extensions, for cross-browser privacy extensions, see Browser extensions#Privacy.

NoScript

NoScript is an extension which disables JavaScript and Flash on any website not specifically whitelisted by the user. This extension will protect you from exploitation of security vulnerabilities by not letting anything but trusted sites (e.g: your bank, webmail) serve you executable content.

Once installed you can configure settings for NoScript by either clicking its icon on the toolbar or right clicking a page and navigating to NoScript. You will then have the option to enable/disable scripts for the current page, as well as any third party scripts that the page is linking to. Alternatively you can choose to enable scripts temporarily for that session only.

Be aware a lot of modern websites use scripts for layout purposes, hence content may look different. For example, failed rendering due to missing fonts might occur on websites that load fonts at runtime via scripts, which were blocked by NoScript.

For more detailed configuration see the NoScript FAQ.

RequestPolicy Continued

RequestPolicy Continued (a successor to the original RequestPolicy) is an extension for Mozilla browsers which lets you have control over cross-site requests. It also lets you blacklist or whitelist requests by default. Disabling unnecessary cross-site requests leads to better privacy, safety and faster browsing.

Note: This addon is currently in the process of being updated for use on modern versions of Firefox (57+).

CanvasBlocker

CanvasBlocker Blocks or fakes the JS-API for modifying <canvas> to prevent Canvas-Fingerprinting.</canvas>

Tip: Firefox has a built-in anti-fingerprinting feature that can be enabled by setting privacy.resistFingerprinting to true in about:config.

Remove system-wide hidden extensions

Several extensions, hidden to the user, are installed by default in /usr/lib/firefox/browser/features. Many can be safely removed via rm extension-name.xpi in order to completely remove unwanted features. Many of these extensions are not enabled by default and have a menu option for enabling or disabling. Note that any files removed will return upon update of the firefox package. To keep these extensions removed, consider adding the directories to NoExtract= in pacman.conf, see Pacman#Skip files from being installed to system. Below are a few examples of these extensions and their features.

  • activity-stream@mozilla.org.xpi - "Activity Stream" which replaces the new tab page. See [2]
  • firefox@getpocket.com.xpi - Pocket

See also [3] for a full list of system extensions including README files describing their functions.

See also