How Internet Censorship Works

Domestic journalists and delegates use the Internet at the Great Hall of the People during a session of the National People's Congress in Beijing.
Frederic J. Brown/AFP/Getty Images

One of the early nicknames for the Internet was the "information superhighway" because it was supposed to provide the average person with fast access to a practically limitless amount of data. For many users, that's exactly what accessing the Internet is like. For others, it's as if the information superhighway has some major roadblocks in the form of Internet censorship.

The motivations for censorship range from well-intentioned desires to protect children from unsuitable content to authoritarian attempts to control a nation's access to information. No matter what the censors' reasons are, the end result is the same: They block access to the Web pages they identify as undesirable.


Internet censorship isn't just a parental or governmental tool. There are several software products on the consumer market that can limit or block access to specific Web sites. Most people know these programs as Web filters. Censorship opponents have another name for them: Censorware.

While there are some outspoken supporters and opponents of Internet censorship, it's not always easy to divide everyone into one camp or another. Not everyone uses the same tactics to accomplish goals. Some opponents of censorship challenge government policies in court. Others take the role of information freedom fighters, providing people with clandestine ways to access information.

In this article, we'll look at the different levels of Internet censorship, from off-the-shelf Web filters to national policy. We'll also learn about the ways some people are trying to fight censorship.

We'll start off by looking at Internet censorship on the domestic level.


Internet Censorship at Home

Web filter programs like Net Nanny use blacklists to block access to Web sites with mature content.
Photo courtesy

There's no denying that the Internet contains a lot of material that most parents wouldn't want their children to see. Whether it's pornography, hate speech, chat rooms or gambling sites, many parents worry that their children will be exposed to negative or even dangerous content. While some opponents of censorship may feel that parental supervision is the best way to keep kids safe online, many parents point out that it's difficult -- if not impossible -- to oversee a child's access to the Internet all the time.

Many parents turn to software and hardware solutions to this problem. They can purchase Web filtering programs like Net Nanny or CYBERsitter to block access to undesirable Web sites. These programs usually have a series of options parents can select to limit the sites their children can access. These options tell the program which filters to enable. For example, CYBERsitter has 35 filter categories, including pornography and social networking sites [source: CYBERsitter].


Most Web filters use two main techniques to block content: Blacklists and keyword blocking. A blacklist is a list of Web sites that the Web filter's creators have designated as undesirable. Blacklists change over time, and most companies offer updated lists for free. Any attempt to visit a site on a blacklist fails. With keyword blocking, the software scans a Web page as the user tries to visit it. The program analyzes the page to see if it contains certain keywords. If the program determines the Web page isn't appropriate, it blocks access to the page.

Another option for parents is to install a firewall. A computer firewall provides protection from dangerous or undesirable content. Firewalls can be software or hardware. They act as a barrier between the Internet and your computer network. They only let safe content through and keep everything else out. Firewalls require a little more involvement from the network administrator (in this case, a parent) than Web filtering software. Tech-savvy parents might not have a problem installing and maintaining a firewall. Others prefer to use Web filters, which do most of the work for them.

Have you ever tried to access a Web site at your workplace only to receive an intimidating message? Some companies limit the kinds of sites employees can visit. Learn about Internet censorship from the corporate standpoint on the next page.



Big Businesses and Internet Censorship

Vinton Cerf, vice president of engineering at Google, speaks on behalf of his company at a debate on net neutrality at the Center for American Progress.
Mark Wilson/

Corporations that restrict employee Internet access usually do so for a few reasons. One of the most common reasons is to increase productivity. While employees can use the Internet for research or communication, they may also use it as a distraction. Some companies restrict Internet access severely in order to prevent employees from wasting time online.

Another corporate concern is harassment. Without restrictions, an employee could surf the Web for inappropriate content, such as pornography. If other employees see this material, they may feel that their work environment is a hostile one. Some companies resort to using Internet censorship in order to avoid lawsuits.


While several companies use Web filtering software similar to the products available for home use, many also rely on firewalls. With a firewall, a company can pick and choose which Web pages or even entire domains to block. This way, the company is more likely to avoid blocking sites that employees may need to access legitimately.

At many workplaces, when an employee attempts to access a restricted Web site, he or she will see a message that says the network administrator has identified the site as inappropriate. Usually the message includes the option to petition the network administrator if the user feels the site is wrongfully blocked. The network administrator can adjust which sites are restricted through firewall settings.

What about the corporations that provide Internet access, such as telecom and cable companies? They can play a crucial role in what content customers can access on the Internet. In the United States, there's an ongoing battle over a concept called net neutrality. In a nutshell, net neutrality refers to a level playing ground where Internet service providers (ISPs) allow access to all content without favoring any particular company or Web site. Telecom and cable companies successfully petitioned the Supreme Court to dismiss net neutrality [source: ACLU].

Without net neutrality, ISPs can charge content providers a fee for bandwidth usage. Content providers that pay the fee will get more broadband access, meaning their Web sites will load faster than competitors who didn't pay the fee. For example, if Yahoo pays a fee to an ISP and Google didn't, the ISP's customers would discover that Yahoo's search engine loads much faster than Google's. Supporters of net neutrality argue that such preferential treatment amounts to censorship.

Keep reading to learn how some nations try to dictate the kind of content citizens access.


Internet Censorship at the International Level

Many countries restrict access to content on the Internet on some level. Even the United States has laws that impact the kind of information you can access on the Internet in a school or public library. Some countries go much further than that -- and a few don't allow any access to the Internet at all.

The OpenNet Initiative (ONI), an organization dedicated to informing the public about Web filtering and surveillance policies around the world, classifies Web filtering into four categories:


  • Political: Content that includes views contrary to the respective country's policies. The political category also includes content related to human rights, religious movements and other social causes
  • Social: Web pages that focus on sexuality, gambling, drugs and other subjects that a nation might deem offensive
  • Conflict/Security: Pages that relate to wars, skirmishes, dissent and other conflicts
  • Internet tools: Web sites that offer tools like e-mail, instant messaging, language translation applications and ways to circumvent censorship

Countries like the United States are fairly liberal, with policies that restrict only a few Web pages, but other countries are stricter. According to Reporters Without Borders, an organization dedicated to promoting free expression and the safety of journalists, the following countries have the strongest censorship policies:

  • Belarus
  • China
  • Cuba
  • Egypt
  • Iran
  • Myanmar
  • North Korea
  • Saudi Arabia
  • Syria
  • Tunisia
  • Turkmenistan
  • Uzbekistan
  • Vietnam

Some countries go well beyond restricting access. The Myanmar government allegedly keeps Internet cafés under surveillance with computers that automatically take screenshots every few minutes. China has an advanced filtering system known internationally as the Great Firewall of China. It can search new Web pages and restrict access in real time. It can also search blogs for subversive content and block Internet users from visiting them. Cuba has banned private Internet access completely -- to get on the Internet, you have to go to a public access point.

There are several organizations dedicated to ending Internet censorship. Find out more about them on the next page.


Opponents of Internet Censorship

In addition to the thousands of people who combat censorship through blogs every day, there are several organizations that raise awareness about Internet censorship. Some are formal organizations with prestigious memberships, while others are looser groups that aren't above advocating a guerilla approach to getting around strict policies.

The American Civil Liberties Union (ACLU) is an adamant opponent of Internet censorship. The ACLU has filed numerous lawsuits in order to overturn censorship laws. In 2007, the ACLU convinced a federal court that the Children's Online Protection Act (COPA) was unconstitutional. COPA was a law that made it illegal to present material online that was deemed harmful to minors, even if it included information valuable to adults [source: ACLU].


The OpenNet Initiative is a group that strives to provide information to the world about the ways countries allow or deny citizens access to information. The initiative includes departments at the University of Toronto, the Harvard Law School, Oxford University and the University of Cambridge. On ONI's Web page you can find an interactive mapthat shows which countries censor the Internet.

Reporters Without Borders also concerns itself with Internet censorship, although the group's scope extends beyond Internet practices. The group maintains a list of "Internet enemies," countries that have the most severe Internet restrictions and policies in place [source: Reporters Without Borders].

The Censorware Project has been around since 1997. Its mission is to educate people about Web filtering software and practices. At its Web site, you can find investigative reports about all the major Web filter programs available on the market as well as essays and news reports about censorship. A similar site is, which began as a site dedicated to protecting free speech on the Internet for young people.

Other groups offer advice on how to disable or circumvent censorware. Some advocate using proxy sites. A proxy site is a Web page that allows you to browse the Web without using your own Internet protocol (IP) address. You visit the proxy site, which includes a form into which you type the URL of the restricted sites you want to visit. The proxy site retrieves the information and displays it. Outsiders can only see that you've visited the proxy site, not the sites you've pulled up.

It may be decades before the Internet reaches its full potential as a conduit for ideas. Ironically, it isn't going to get there through technological breakthroughs, but through changes in national and corporate policies.

To learn more about Internet censorship and related topics, check out the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links

  • Anderson, Mark. "Internet Censorship: As Bad As You Thought It Was." IEEE Spectrum. November 2007.
  • Children's Internet Protection Act. Federal Communications Commission.
  • Cohn, William A. "Yahoo's China Defense." The New Presence. Autumn 2007. Page 30.
  • Cook, Steven and Levi, Michael. "Tangled Web." Wall Street Journal. March 22, 2007.
  • Dobija, Jane. "The First Amendment Needs New Clothes." American Librarians. September 2007. pp. 50-53.
  • Finkelstein, Seth. "CIPA ruling as censoreware argument handbook." June 6, 2002.
  • Finkelstein, Seth. "An anticensorware investigation by Seth Finkelstein." November 16, 2000.
  • "Google censors self for China." BBC News. January 25, 2006.
  • Hogge, Becky. "Think of the children." New Statesman. October 22, 2007. Page 50.
  • "Internet." (2008). In Encyclopædia Britannica. Retrieved January 22, 2008, from Encyclopædia Britannica Online:
  • Lee, Jennifer. "Cracking the Code of Online Filtering." The New York Times. July 19, 2001.
  • Lipschutz, Robert P. "Web Content Filtering: Don't Go There." PC Magazine. March 16, 2004.,4149,1538777,00.asp
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  • OpenNet Initiative.
  • Quirk, Matthew. "The Web Police." The Atlantic Monthly. May, 2006. pp. 50-51.
  • Reporters Without Borders.
  • Sarrel, Matthew D. "Web Content Filtering." PC Magazine. August 1, 2007.,1759,2164497,00.asp
  • The Censorware Project.