Understanding and using the Tor network

Active Content

Tor is merely responsible for transmitting data – not for content security. Thus, even though you use Tor to transmit data, it's quite possible to reveal the client's identity through Flash, cookies, or JavaScript, for example. Here is where precautions beyond Tor are important.

The most trusted method is the Privoxy [5] content filter. It's available for download from the default Ubuntu repositories, which makes it easily installed via the package manager. Start the filter proxy with /etc/init.d/privoxyd start.

To use Privoxy together with Tor, open the /etc/privoxy/config file with root privileges in a text editor. To have Privoxy forward the received data, add the following line at the beginning:

forward-socks4a / localhost:9050 .

A restart using /etc/init.d/privoxyd restart loads in the change. Next, visit the 127.0.0.1:8118 address in the browser and enable the check box Use this proxy server for all protocols. When successful, the http://p.p URL (Figure 4) opens the Privoxy home page. To check whether Tor is running in the cascade, visit https://check.torproject.com.

Figure 4: After a successful setup, the Privoxy home page appears with the URL http://p.p.

Conclusion

Tor isn't a completely failsafe solution for safe surfing, but it does make things very difficult for snoopers and crackers. Because the system is decentralized, it's much more resistant to attacks than other anonymizing services. Furthermore, the onion routing design currently provides the safest way to use the web anonymously in that it requires a considerable effort to circumvent its working model.

Whereas past versions of Tor were largely unusable because of its low transfer rate, things have turned around drastically. In my test, the throughput was consistently above the 100KB/s mark, which is more than enough for surfing, but it may test users' patience during larger downloads. However, the Tor network isn't really meant for such applications anyway. l