tage,” he notes. As a result, numerous YouTube and Twitter knockoffs exist in some countries, including China, and other countries block services such as Skype in order to protect gov-ernment-run telephone services and other businesses.

Breaching censors’ Walls

Increasingly, students, dissidents, journalists, bloggers, human rights advocates, and others are challenging Internet censorship. In the digital age, they’re fighting back with an arsenal of tools such as proxy servers that circumvent filtering by masking the user and altering the way data flows to a Web server or by VPNs that tunnel through to other less censorious countries.

It’s a cat-and-mouse game, to be sure. As individuals begin downloading and using proxy servers, it’s common for government censors to detect the activity and block downloads, as well as the proxies. However, the same applications frequently become available at alternative sites and through peer-to-peer services. Moreover, new proxy servers continually spring up. But VPNs represent a different challenge, and most censoring countries are hesitant to block them because they’re essential for commerce and used heavily by foreign business leaders and diplomats.

Some services, like Tor, a free program offered by the nonprofit Tor Project, circumvent censorship by routing communications across a distributed network of relays located around the world. These VPN tunnels make it possible to access blocked pages and sites,

china, like many
countries that
practice internet
censorship,
blocks Web sites
sporadically and in
no systematic way.

such as Facebook or YouTube. They also allow journalists and dissidents to publish Web sites and other services without revealing their location.

Another free VPN application, AnchorFree Hotspot Shield, enables users to view otherwise censored Web sites by converting the http protocol to an encrypted https protocol and providing users with a virtual identity. “Although the product was originally intended to serve as a universal privacy and security offering, a growing number of people are looking for a way to bypass controls and access information freely,” says AnchorFree CEO David Gorodyansky.

Both Tor Project and AnchorFree’s
Web sites are blocked in China. Nev-
ertheless, Gorodyansky claims that
usage in China has doubled since the
Chinese government began blocking
the site last summer. Potential users
download Tor and AnchorFree Hot-
spot Shield by visiting mirror sites or
by sending the companies an email
message and receiving a message
with a Windows- or Mac-compatible
file. In addition, individuals share ap-
plications with USB flash drives and
through peer-to-peer services.

Further Reading

Deibert, R.J., Palfrey, J.G., Rohozinskiand, R., Zittrain, J. (Eds.)

Access Denied: The Practice and Policy of Global Internet Filtering, MIT Press, Cambridge, MA, 2008. Fallows, J. “The Connection has Been Reset,” The Atlantic, March 2008.

Farrar, L.

Cashing in on Internet censorship, Cnn. com, February 19, 2010, http://www.cnn. com/2010/TECh/02/18/internet.censorship. business/ index.html.

Reporters Without Borders Enemies of the Internet, Reporters Without Borders, March 12, 2010, http://www.rsf. org/IMG/pdf/Internet_enemies.pdf.

Samuel Greengard is an author and journalist based in West linn, oR.

© 2010 ACM 0001-0782/10/0700 $10.00

Social;Media
CMU Researchers Analyze Twitter Sentiments

a computer analysis of people’s sentiments in a billion Twitter messages during 2008 and 2009 yielded measures of consumer confidence and presidential job approval similar to those of public opinion polls, according to Carnegie Mellon University researchers.

The findings suggest that
analyzing the text in tweets could
be an inexpensive, rapid means
of gauging public opinion on
some subjects, says Noah smith,
assistant professor of language
technologies and machine
learning at Carnegie Mellon.
however, the tools for extracting
public opinion from the text of
social media are crude and social
media remain in their infancy,
smith says, so the extent to which
these methods could supplement
or replace traditional public
opinion polls is unknown.

Twitter-derived consumer sentiment measurements were much more volatile day-to-day than the polling data, but when the researchers “smoothed” the results by averaging them over a period of days, the results often correlated closely with the polling data, says brendan o’Connor, a graduate student in Carnegie Mellon’s Language Technologies institute and first author of the study.