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Torbutton is a 1-click way for Firefox users to enable or disable the
browser's use of Tor. It adds a panel to the statusbar that says "Tor
Enabled" (in green) or "Tor Disabled" (in red). The user may click on the
panel to toggle the status. If the user (or some other extension) changes
the proxy settings, the change is automatically reflected in the
statusbar.

Some users may prefer a toolbar button instead of a statusbar panel. Such
a button is included, and one adds it to the toolbar by right-clicking on
the desired toolbar, selecting "Customize...", and then dragging the
Torbutton icon onto the toolbar. There is an option in the preferences to
hide the statusbar panel (Tools->Extensions, select Torbutton, and click
on Preferences).

Newer Firefoxes have the ability to send DNS resolves through the socks
proxy, and Torbutton will make use of this feature if it is available in
your version of Firefox.

                               FAQ

1. I can't click on links or hit reload after I toggle Tor! Why?

   Due to Firefox Bug 409737, pages can still open popups and perform
   Javascript redirects and history access after Tor has been toggled. These
   popups and redirects can be blocked, but unfortunately they are
   indistinguishable from normal user interactions with the page (such as
   clicking on links, opening them in new tabs/windows, or using the history
   buttons), and so those are blocked as a side effect. Once that Firefox bug
   is fixed, this degree of isolation will become optional (for people who do
   not want to accidentally click on links and give away information via
   referrers). A workaround is to right click on the link, and open it in a
   new tab or window. The tab or window won't load automatically, but you can
   hit enter in the URL bar, and it will begin loading. Hitting enter in the
   URL bar will also reload the page without clicking the reload button.

2. My browser is in some weird state where nothing works right!

   Try to disable Tor by clicking on the button, and then open a new window.
   If that doesn't fix the issue, go to the preferences page and hit 'Restore
   Defaults'. This should reset the extension and Firefox to a known good
   configuration. If you can manage to reproduce whatever issue gets your
   Firefox wedged, please file details at the bug tracker.

3. When I toggle Tor, my sites that use javascript stop working. Why?

   Javascript can do things like wait until you have disabled Tor before
   trying to contact its source site, thus revealing your IP address. As
   such, Torbutton must disable Javascript, Meta-Refresh tags, and certain
   CSS behavior when Tor state changes from the state that was used to load a
   given page. These features are re-enabled when Torbutton goes back into
   the state that was used to load the page, but in some cases (particularly
   with Javascript and CSS) it is sometimes not possible to fully recover
   from the resulting errors, and the page is broken. Unfortunately, the only
   thing you can do (and still remain safe from having your IP address leak)
   is to reload the page when you toggle Tor, or just ensure you do all your
   work in a page before switching tor state.

4. When I use Tor, Firefox is no longer filling in logins/search boxes for
   me. Why?

   Currently, this is tied to the "Block history writes during Tor" setting.
   If you have enabled that setting, all formfill functionality (both saving
   and reading) is disabled. If this bothers you, you can uncheck that
   option, but both history and forms will be saved. To prevent history
   disclosure attacks via Non-Tor usage, it is recommended you disable
   Non-Tor history reads if you allow history writing during Tor.

5. Which Firefox extensions should I avoid using?

   This is a tough one. There are thousands of Firefox extensions: making a
   complete list of ones that are bad for anonymity is near impossible.
   However, here are a few examples that should get you started as to what
   sorts of behavior are dangerous.

    1. StumbleUpon, et al These extensions will send all sorts of information
       about the websites you visit to the stumbleupon servers, and correlate
       this information with a unique identifier. This is obviously terrible
       for your anonymity. More generally, any sort of extension that
       requires registration, or even extensions that provide information
       about websites you visit should be suspect.
    2. FoxyProxy While FoxyProxy is a nice idea in theory, in practice it is
       impossible to configure securely for Tor usage without Torbutton. Like
       all vanilla third party proxy plugins, the main risks are plugin
       leakage and history disclosure, followed closely by cookie theft
       by exit nodes and tracking by adservers (see the Torbutton
       Adversary Model for more information). However, even with Torbutton
       installed in tandem and always enabled, it is still very difficult
       (though not impossible) to configure FoxyProxy securely. Since
       FoxyProxy's 'Patterns' mode only applies to specific urls, and not to
       an entire tab, setting FoxyProxy to only send specific sites through
       Tor will still allow adservers to still learn your real IP. Worse, if
       those sites use offsite logging services such as Google Analytics, you
       may still end up in their logs with your real IP. Malicious exit nodes
       can also cooperate with sites to inject images into pages that bypass
       your filters. Setting FoxyProxy to only send certain URLs via Non-Tor
       is much more viable, but be very careful with the filters you allow.
       For example, something as simple as allowing *google* to go via
       Non-Tor will still cause you to end up in all the logs of all websites
       that use Google Analytics! See this question on the FoxyProxy FAQ
       for more information.
    3. NoScript Torbutton currently mitigates all known anonymity issues with
       Javascript. While it may be tempting to get better security by
       disabling Javascript for certain sites, you are far better off with an
       all-or-nothing approach. NoScript is exceedingly complicated, and has
       many subtleties that can surprise even advanced users. For example,
       addons.mozilla.org verifies extension integrity via Javascript over
       https, but downloads them in the clear. Not adding it to your
       whitelist effectively means you are pulling down unverified
       extensions. Worse still, using NoScript can actually disable
       protections that Torbutton itself provides via Javascript, yet still
       allow malicious exit nodes to compromise your anonymity via the
       default whitelist (which they can spoof to inject any script they
       want).

6. Which Firefox extensions do you recommend?

    1. RefControl Mentioned above, this extension allows more
       fine-grained referrer spoofing than Torbutton currently provides. It
       should break less sites than Torbutton's referrer spoofing option.
    2. SafeCache If you use Tor excessively, and rarely disable it, you
       probably want to install this extension to minimize the ability of
       sites to store long term identifiers in your cache. This extension
       applies same origin policy to the cache, so that elements are
       retrieved from the cache only if they are fetched from a document in
       the same origin domain as the cached element.

7. Are there any other issues I should be concerned about?

   There is currently one known unfixed security issue with Torbutton: it is
   possible to unmask the javascript hooks that wrap the Date object to
   conceal your timezone in Firefox 2, and the timezone masking code does not
   work at all on Firefox 3. We are working with the Firefox team to fix one
   of Bug 399274 or Bug 419598 to address this. In the meantime, it
   is possible to set the TZ environment variable to UTC to cause the browser
   to use UTC as your timezone. Under Linux, you can add an export TZ=UTC to
   the /usr/bin/firefox script, or edit your system bashrc to do the same.
   Under Windows, you can set either a User or System Environment
   Variable for TZ via My Computer's properties. In MacOS, the situation is
   a lot more complicated, unfortunately.

   In addition, RSS readers such as Firefox Livemarks can perform periodic
   fetches. Due to Firefox Bug 436250, there is no way to disable
   Livemark fetches during Tor. This can be a problem if you have a lot of
   custom Livemark urls that can give away information about your identity.