Hiding from Spies

Tor, which was originally known as "The Onion Router," [1] is an anonymous networking solution that has recently gained popularity as a means to avoid government snooping and commercial behavior tracking. A Tor client, running on a desktop system, routes traffic to an anonymous network consisting of Tor nodes.

Tor relies on the onion principle (Figure 1) and redirects the traffic through three nodes, changing the route every 10 minutes. The Tor Browser Bundle comes with a preconfigured combination of the Firefox web browser, the Tor client, and Tor Launcher.

Figure 1: Schematic representation of the Tor approach. Whether the red dashed line from the exit node to the destination server really is unencrypted depends on the protocol used (HTTP or HTTPS).

The complete Tor package lets you surf the web in relative anonymity and use services such as email, instant messaging, IRC, SSH, and P2P. Although the Tor project offers its own user interface for its anonymous router in the form of Vidalia, the alternative SelekTOR front end provides some functions that Vidalia lacks. For example, SelekTOR offers semi-automatic configuration of the Tor client, as well as a choice of exit nodes sorted by country.

In this article, I show how to configure and use the SelekTOR front end. I'll assume you have some basic familiarity with Tor. For an introduction to the Tor anonymity solution, see the project website [2]. The developer points out that SelekTOR is only an interface for the Tor client and launcher, not a substitute for the Tor browser.

Requirements

SelekTOR supports Firefox or its offshoot Pale Moon, as well as Opera and Chrome or Chromium, with no additional plugins. The program does require an installed Java runtime environment (JRE)  7 or its free implementation, OpenJRE  1.7. Only the next version of the software will have Java 8 support.

If Vidalia is already installed, you must remove it before using SelekTOR. You also need to remove any existing older version of SelekTOR before installing the new version. The current SelekTOR 3 (November 2014 version) release has a version number of 3.12-11.

Although the software was written in Java, separate versions exist for Linux and Windows, and only the Windows version comes with the Tor software (see the "Installing SelekTOR" box). The software works with all major desktop environments on Linux.

Defining Exit Nodes

After starting the SelekTOR GUI, first make sure that Tor has started correctly. After restarting the browser, you can visit the Tor check site to do so [4]. You can then see whether you are visiting the site with or without Tor. You should also see an IP address that differs from the external address otherwise allocated for this connection.

SelekTOR is suitable for several applications. In addition to its role as a Tor launcher, it offers you the option of defining the exit nodes yourself. Exit nodes are the Tor servers through which the packets leave the Tor network and enter the normal Internet ("clearnet"). They are a vulnerability in the Tor system, because if you use an unencrypted connection, an attacker can crack your anonymity by sniffing the exit nodes, provided they have sufficient resources and perseverance. However, they have to do so in less than 10 minutes, because Tor then automatically switches the route.

With SelekTOR, you can select the exit node from a list sorted by country (Figure  2). Additionally, the software offers a selective routing based on URL patterns. These patterns rely on PAC files (proxy auto-config) [5] for different websites to use the most appropriate proxy automatically.

Figure 2: Among other things, SelekTOR lets you choose the exit nodes yourself.

Put simply, a proxy is a broker that routes requests through its own address before passing them on to their actual origin in order to obfuscate the original source. The PACs include the hostname and the port number of a proxy in a few lines of Java code. They are mostly on servers on the Internet but can also be operated locally. This setup allows users in countries whose governments block certain websites to use them anyway. SelekTOR includes a Proxy Pattern Editor (under Menu) that lets you create, edit, import, and export PAC files.

SelekTOR also tries to optimize the function of the Tor client by continuously monitoring the connections and using the exit nodes with the best response times. The software integrates the WHOIS protocol for querying information about Internet domains and IP addresses and their owners (Figure 3). With the release of version 3.12-11, whois became an integrated web application; therefore, like Atlas [6], which visualizes information on Tor relays (Figure 4), it can be initiated in the browser and sent via Tor.

Figure 3: The whois query in a pre-3.12-11 version shows information about the selected node.

Figure 4: Clicking the Details button in the main window launches the Atlas query in the web browser, which gives you detailed information about the respective Tor server.

Conclusions

SelekTOR simplifies use of the Tor client in many ways and makes using Tor more transparent for the user. Additionally, the software lets you bypass restrictions of a political or commercial nature when accessing web pages. In doing so, SelekTOR handles the configuration for most applications unobtrusively in the background, instead of overwhelming the user with what can be a difficult task.

During testing in the lab, SelekTOR provided its service perfectly after resolving some troubles caused by bugs. If problems occur during use, contact the friendly and helpful developer [7]. While researching this article, I collaborated with the developer on removing some minor bugs.