Circumventing Internet Blocking With Tor

Dec. 26, 2009

There has been significant recent talk, in Europe and Australia, of imposing blocking of objectionable web sites, including revisionist ones. The purpose of this message is to call to your attention one way of circumventing such censorship. It is also a method of concealing your identity from a target web site. It works best if you use the Firefox browser.

An article in Technology Review (May/June 2009, pp. 60+) on the “Tor Project” actually lists 5 systems for doing this, of which Tor is considered both “more secure for the most users” and “slowest of the tested tools”.

Suppose You want to look at website Target. The usual arrangement is

You —— Target

i.e. there is essentially a direct connection between You and the Target.

Tor, via the application vidalia.app (the icon is an onion and I am using Macintosh terminology), lets you set up the following alternative:

You — A — B — C — Target

i.e. You are connected to Target via intermediate nodes A, B, C which are generally physically located in the USA or other safe location. Somebody trying to block your access to forbidden sites knows only that you are looking at A. Note that the normal blocking we are dealing with here works not by examining a web page's content but its Internet address.

Whenever you run the program vidalia.app you get a new set of intermediate servers or nodes (A,B,C). The application vidalia.app can be downloaded from http://www.torproject.org/index.html.en.

To use Tor, certain special settings are necessary for your browser, and this is where the “Torbutton”, available as a Firefox add-on, is very helpful. It can be downloaded from https://addons.mozilla.org/en-US/firefox/addon/foxtor/. When it is installed one sees, at the lower right of the Firefox window, either “Tor Disabled” (in red) or “Tor Enabled” (in green). Clicking on these two words toggles the user between the two states. Normal use of Firefox, without Tor, has “Tor Disabled”.

At the Tor Project web site, I get the impression that for Windows users both Vidalia and the Torbutton are available in a single download, but I haven't tried it.

A typical use of Tor would be as follows. It is assumed Firefox is not open.

1. Open vidalia.app . This will take one or two minutes to establish a path such as A – B – C for you. Leave Vidalia open as long as you need the Tor network.
2. Open Firefox and click on “Tor Disabled”; it will turn to “Tor Enabled”.
3. Connect to the Target web site in the normal way. Things will work slower than normal.
4. Do whatever you wish at the Target. Some web sites may be quirky, but I have had no trouble with major revisionist web sites.
5. When done click on “Tor Enabled” to return to “Tor Disabled” and quit Vidalia. Quit Firefox.

The next time you open Vidalia, you get a new path. Also, the path will change during one session with Vidalia if you switch your attention to a different web site.

My recommendation is that all revisionists have, and know how to use, anti-blocking software. Americans usually don't have a problem with Internet blocking but there will be special cases, even for them, where special measures such as Tor are needed to view a web site. Europeans who connect to the Internet with laptop computers they bring to Internet cafes, or other providers of wireless Internet access, have the most urgent need. Such providers of wireless Internet access are the most vulnerable to official orders. I suggest you get the software now, because there is a chance that the Tor Project sites may themselves be blocked in the future.

There is another side to this that relates to all equally. You may wish to view a web site without the Target being able to learn your Internet address. Tor makes such anonymous contact possible; the Target can learn only that he is being contacted by C. Some police agencies and private companies use Tor for this purpose, to prevent the Target from learning who is observing him.

As for official countermeasures to Tor, we should consider that the Internet addresses of all these intermediate nodes are publicly available. However, their number is continually being augmented with new nodes and it is very difficult for a censor to block forbidden sites viewed this way.

Each node in your path has your computer's addressing data, but it is securely encrypted against external observation. Moreover, there are legal obstacles to official action against Tor, which is not a provider of forbidden content, and can be used to view web sites that are not forbidden. Operators of the nodes presumably have no interest in the traffic passing through them. Also, Tor is an effective way to make anonymous contact, which I assume will remain legal for a long while.

Finally, I have to say you do all this at your own risk. The publisher and I can't be held responsible for what happens on remote computers with free software, and I have tested Tor only on my Macintosh. The package is reasonably simple so, if you get in trouble, the problem is probably peculiar to you and a person close to you would be the most likely to be able to diagnose it.