SecBrowser ™ in Qubes OS: A Security-hardened, Non-anonymous Browser
- 1 Introduction
- 2 Security Enhancements
- 3 Privacy and Fingerprinting Resistance
- 4 Install SecBrowser ™
- 5 SecBrowser Settings and Configuration
- 6 FAQ
- 7 Non-Affiliation with The Tor Project
- 8 Footnotes
SecBrowser ™ is a derivative of the Tor Browser Bundle (which itself is a derivative of Mozilla Firefox) but without Tor. This means unlike Tor Browser, SecBrowser ™ does not route traffic over the Tor network, which in common parlance is referred to as "clearnet" traffic. Even without the aid of the Tor network, SecBrowser ™ still benefits from the numerous patches [archive] that Tor developers have merged into the code base. Even with developer skills, these enhancements would be arduous and time-consuming to duplicate in other browsers, with the outcome unlikely to match SecBrowser's ™ many security benefits. While browser extensions can be installed to mitigate specific attack vectors, this ad hoc approach is insufficient. SecBrowser ™ leverages the experience and knowledge of skilled Tor Project developers, and the battle-tested Tor Browser.
Table: SecBrowser ™ Security and Privacy Benefits
|Security Slider||Enables improved security by disabling certain web features that can be used as attack vectors.|
|Default Tor Browser Add-ons||
|Firejail (Linux only)||Firejail will be used as a sandboxing measure to restrict the SecBrowser process. |
|Homograph Attack Protection||Fixes the internationalized domain name (IDN) homograph attack vulnerability [archive] present in standard Firefox and Tor Browser releases.  |
|Reproducible Builds||Build security is achieved through a reproducible build process that enables anyone to produce byte-for-byte identical binaries to the ones the Tor Project releases.|
|WebRTC Disabled by Default||WebRTC can compromise the security of VPN tunnels, by exposing the external (real) IP address of a user.|
Privacy and Fingerprinting Resistance
Research from a pool of 500,000 Internet users has shown that the vast majority (84%) have unique browser configurations and version information which makes them trackable across the Internet. When Java or Flash is installed, this figures rises to 94%. SecBrowser ™ shares the fingerprint with around three million [archive] other Tor Browser users, which allows people who use SecBrowser ™ to "blend in" with the larger population and better protect their privacy.
- Use of Torbutton, which is bundled with SecBrowser ™ and enabled by default.
- Use of mobile devices like Android and iPhone.
- Corporate desktop machines which are clones of one another.
- The User Agent is uniform for all Torbutton users.
- Plugins are blocked.
- The screen resolution is rounded down to 50 pixel multiples.
- The timezone is set to GMT.
- DOM Storage is cleared and disabled.
Note: Because tracking techniques are complex, Panopticlick does not measure all forms of tracking and protection.
- SecBrowser ™ conveys 6.26 bits of identifying information.
- One in 76.46 browsers have the same fingerprint.
- Browsers that convey lower bits of identification are better at resisting fingerprinting.
Table: Tor Browser vs SecBrowser ™ HTTP headers comparison.
Percentage (%) out of 1652 with fingerprints tags [Firefox,Windows]:
|User-Agent||Mozilla/5.0 (Windows NT 6.1; rv:60.0) Gecko/20100101 Firefox/60.0||2.48||2.42|
|Accepting-Encoding||gzip, deflate, br||82.14||82.13|
Install SecBrowser ™
SecBrowser ™ can be installed using tb-updater [archive] which is a package developed and maintained by Whonix developers. When run,
tb-updater seamlessly automates the download and verification of SecBrowser ™ (from The Tor Project's website). One of the many benefits of
tb-updater is the ability to disable Tor is prebuilt into the software. This improves usability and is convenient since a security-focused clearnet browser (SecBrowser ™), is readily available. To start SecBrowser ™ users can choose between the start menu, command line or create a desktop starter. Unlike other manual methods of disabling Tor, this greatly simplifies the procedure and lessens the chance of a configuration error.
New Qubes TemplateBasedVMs: Latest Tor Browser Version
Optional. It is possible to have a copy of the latest Tor Browser version made available to all freshly created AppVMs and DispVMs based upon the TemplateVM. Run the following command in the TemplateVM. 
sudo touch /etc/secbrowser-qubes
This setting utilizes the same mechanism used by Whonix to download Tor Browser in the Whonix-Workstation TemplateVM. See also: tb-updater in Qubes TemplateVM. When using this setting, when the tb-updater package is updated,
download-secbrowser runs automatically.
The first step to install
tb-updater is to add the Whonix repository. 
In the Debian TemplateVM, update the packages lists.
sudo apt-get update
sudo apt-get install --no-install-recommends secbrowser
Download SecBrowser ™
Manually In TemplateVM
If tb-updater has not been updated yet, Qubes users can run the following command in Qubes TemplateVM.
You will be presented with
QUESTION: Download now? followed by choice of 3 options.
n/9.0.2/9.5a3 (Version is at the time of writing this documentation.) The default is
n which stands for "no" if you just press the
Enter key. Otherwise type in the full version number to indicate your choice of either the stable release (i.e.
9.0.2) or the alpha release (
When the download completes & is verified successfully, you will be prompted whether to
Install now?. Type in
y to proceed.
Power off the TemplateVM after installation so these changes can propagate to newly started TemplateBasedVMs.
SecBrowser ™ can be installed simply by running
download-secbrowser in the Debian TemplateVM.
In the Debian TemplateVM, run.
Tor Browser Internal Updater
It is still possible to use the Tor Browser Internal Updater in TemplateBasedVMs.
Start SecBrowser ™
SecBrowser ™ can be started from Qubes start menu.
Alternatively, run this command in a AppVM or DispVM terminal.
Alternatively, run this command in a
qvm-run <appvm_name> secbrowser
SecBrowser Settings and Configuration
TemplateVM vs AppVM
If users edit the TemplateVM to modify SecBrowser ™ behavior, all AppVMs created thereafter will inherit those changes. However, AppVMs created prior to the aforementioned edits will not benefit from any changes to the SecBrowser ™ configuration file in the TemplateVM.
While SecBrowser ™ has numerous security enhancements they can come at a cost of decreased usability. Since it is also highly configurable, security settings and behavior can be customized according to personal requirements.
Note: The following configuration steps are run the Debian AppVM.
SecBrowser ™ has a “Security Slider” in the shield menu. This can increase security [archive] by disabling certain web features that are possible attack vectors. By default, the Security Slider is set to “Safest” which is the highest security level. This security level will prevent some web pages from functioning properly, so security needs must be weighed against the degree of usability that is required.
Private Browsing Mode
In the default configuration Tor Browser has private browsing mode enabled. This setting prevents browsing and download history as well as cookies from remaining persistent across SecBrowser ™ restarts. However,
tb-starter includes a custom
user_pref that disables private browsing mode when SecBrowser ™ is used.
When private browsing mode is disabled SecBrowser ™'s built-in "long-term linkability" protections are deactivated. This means users are vulnerable to attacks which can link activities between earlier and later browsing sessions. If privacy is paramount users can enable private browsing mode by commenting out the corresponding user preference.
If you prefer to keep private browsing mode disabled, it may be advantageous to install one or more anti-tracking browser extensions. The extensions Disconnect [archive], Privacy Badger [archive] and uBlock Origin [archive] are all open-source and are generally recommended. Research which one(s) may be most suitable in the circumstances; their use cases are different.
Persistent NoScript Settings
tb-starter includes a
user_pref that allows custom NoScript settings to persist across browser sessions. This is also a security vs usability trade-off. If the SecBrowser ™ “Security Slider” setting is changed afterwards, all NoScript preferences are overridden and all custom, per-site settings are lost. This holds true regardless of whether the security setting was increased or decreased.
If the persistent NoScript setting is undesirable, this can easily be disabled by commenting out the corresponding
Remember Logins and Passwords for Sites
To increase usability, SecBrowser ™ can (by default) save site login information such as user names or passwords. This usability improvement was implemented by setting
true, which allows this information to be saved across browser sessions.
If you prefer to disable this feature open
user.js in an editor and comment out the corresponding
SecBrowser ™ no longer opens with a red background and a message stating "Something Went Wrong!" Tor is not working in this browser.  This warning was disabled by toggling the user preference
Download Alpha Versions
Whonix developers focus their efforts on advanced anonymity with Tor being a core component. Why develop a package that disables Tor?
tb-upater was developed with design goals focused on securely downloading and verifying Tor Browser. However, requirements for a new operating system under development -- a security focused OS based on Hardened Debian [archive] (Kicksecure) -- called for a security hardened clearnet browser. SecBrowser ™ (Tor Browser without Tor) met those requirements. Hence, the
secbrowser wrapper that disables Tor was integrated into
What is Clearnet?
This term has two meanings:
- Connecting to the regular Internet without the use of Tor or other anonymity networks; and/or
- Connecting to regular servers which are not onion services, irrespective of whether Tor is used or not.
How does SecBrowser ™ disable Tor?
SecBrowser ™ supports custom user preferences
"user_pref" which can be used to change browser configuration and behavior. In
tb-starter the user preferences that disable Tor are located in /usr/share/secbrowser/user.js . When SecBrowser ™ starts this file is copied over to the corresponding SecBrowser ™ profile where the custom
user_pref(s) are parsed.
Tor is disabled by setting the following three preferences to false.
user_pref("extensions.torbutton.startup", false); user_pref("extensions.torlauncher.start_tor", false); user_pref("network.proxy.socks_remote_dns", false);
Can I use SecBrowser ™ in a Whonix-Workstation VM (
VMs behind Whonix-Gateway (
sys-whonix) are always routed through Tor, meaning traffic would still be torified. However, this is strongly recommended against because using SecBrowser ™ will break Tor Browser's per tab stream isolation.
Can I use SecBrowser ™ in a VM torified by something other than Whonix to avoid Tor over Tor?
This is strongly recommended against because using SecBrowser ™ will break Tor Browser's per tab stream isolation. A complete implementation compatible with Tor Browser's per tab stream isolation would be much better.
Does the SecBrowser ™ option alter any other browser behavior?
No, the only changes to SecBrowser ™ are to the preferences previously shown.
Can I add my own custom preferences to change SecBrowser ™ behavior?
Yes, but this could degrade security and privacy. See: SecBrowser ™ Settings.
I have an idea to improve SecBrowser ™'s security. Can I submit a patch?
Many security enhancements, such as (in theory) adding compile time hardening options, need to be submitted upstream to The Tor Project. Patches to
tb-starter or this wiki entry are always welcome!
Non-Affiliation with The Tor Project
SecBrowser ™ is a derivative of Tor® Browser, produced independently from the Tor® anonymity software and carries no guarantee from The Tor® Project [archive] about quality, suitability or anything else.
- https://2019.www.torproject.org/projects/torbrowser/design/ [archive]
- https://tb-manual.torproject.org/security-slider/ [archive]
- https://www.eff.org/https-everywhere [archive]
- https://en.wikipedia.org/wiki/NoScript [archive]
- https://forums.whonix.org/t/automatically-firejailing-tor-browser/4767 [archive]
- For further information, see: very hard to notice Phishing Scam - Firefox / Tor Browser URL not showing real Domain Name - Homograph attack (Punycode) [archive]. Without this change, URLs can be spoofed so users are deceived about what remote server they are communicating with, via substitution of characters that look alike ('homographs').
- https://bugzilla.mozilla.org/show_bug.cgi?id=1332714 [archive]
- https://2019.www.torproject.org/projects/torbrowser/design/ [archive]
- https://blog.torproject.org/deterministic-builds-part-two-technical-details [archive]
- https://en.wikipedia.org/wiki/WebRTC#Concerns [archive]
- https://torrentfreak.com/huge-security-flaw-leaks-vpn-users-real-ip-addresses-150130/ [archive]
- https://www.eff.org/deeplinks/2010/05/every-browser-unique-results-fom-panopticlick [archive]
- https://blog.torproject.org/effs-panopticlick-and-torbutton [archive]
- https://33bits.wordpress.com/about/ [archive]
- https://forums.whonix.org/t/todo-research-and-document-how-to-use-tor-browser-for-security-not-anonymity-how-to-use-tbb-using-clearnet/3822/54 [archive]
- https://github.com/Whonix/tb-updater/blob/master/debian/tb-updater.postinst [archive]
- However, as outlined in this Qubes issue [archive], downloading GPG keys with APT will fail in TemplateVMs. To work around this issue the signing key can be downloaded in an AppVM and copied over to the Debian TemplateVM in a text file.
- See: NoScript Custom Setting Persistence.
- This notice is related to Tor Browser (with Tor) and can be safely ignored.
- https://github.com/Whonix/tb-starter/commit/9e5356263d31511e69980b3afdb70e3396d3cc05 [archive]
- https://github.com/Whonix/tb-updater/commit/798e23c1f9ac1f0ccdfe22c2f79fb0e9f637e51e [archive]
- https://github.com/Whonix/tb-starter/commit/a9219fc2632f667c109cfcdc7e85fff462a60ed3 [archive]
- https://github.com/Whonix/tb-starter/blob/28102df140f3f0f8a9b1bd5bc7dc19336420ccce/usr/bin/torbrowser#L354-L365 [archive]
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