The spread of information networks is forming a new nervous system for our planet. When something happens in Haiti or Hunan, the rest of us learn about it in real time – from real people. And we can respond in real time as well. Americans eager to help in the aftermath of a disaster and the girl trapped in the supermarket are connected in ways that were not even imagined a year ago, even a generation ago. That same principle applies to almost all of humanity today.

Now, in many respects, information has never been so free. There are more ways to spread more ideas to more people than at any moment in history. And even in authoritarian countries, information networks are helping people discover new facts and making governments more accountable. During his visit to China in November, President Obama defended the right of people to freely access information, and said that the more freely information flows, the stronger societies become. He spoke about how access to information helps citizens hold their own governments accountable, generates new ideas, encourages creativity and entrepreneurship.

Amid this unprecedented surge in connectivity, we must also recognise that these technologies are not an unmitigated blessing. These tools are also being exploited to undermine human progress and political rights. The same networks that help organise movements for freedom also enable al-Qaida to spew hatred and incite violence against the innocent. And technologies with the potential to open up access to government and promote transparency can also be hijacked by governments to crush dissent and deny human rights. In the last year, we've seen a spike in threats to the free flow of information. China, Tunisia, and Uzbekistan have stepped up their censorship of the internet. In Vietnam, access to popular social networking sites has suddenly disappeared. And last Friday in Egypt, 30 bloggers and activists were detained.

On their own, new technologies do not take sides in the struggle for freedom and progress, but the United States does. We stand for a single internet where all of humanity has equal access to knowledge and ideas.

We need to synchronise our technological progress with our principles. The internet is a network that magnifies the power and potential of all others. And that's why we believe it's critical that its users are assured certain basic freedoms. Freedom of expression is first among them. But even as networks spread to nations around the globe, virtual walls are cropping up in place of visible walls.

Some countries have erected electronic barriers that prevent their people from accessing portions of the world's networks. They've expunged words, names, and phrases from search engine results. They have violated the privacy of citizens who engage in non-violent political speech. These actions contravene the Universal Declaration on Human Rights, which tells us that all people have the right "to seek, receive and impart information and ideas through any media and regardless of frontiers." With the spread of these restrictive practices, a new information curtain is descending across much of the world. And beyond this partition, viral videos and blogposts are becoming the samizdat of our day.

As in the dictatorships of the past, governments are targeting independent thinkers who use these tools. We've seen reports that when Iranians living overseas posted online criticism of their nation's leaders, their family members in Iran were singled out for retribution. And despite an intense campaign of government intimidation, brave citizen journalists in Iran continue using technology to show the world and their fellow citizens what is happening inside their country.

Now, all societies recognise that free expression has its limits. We do not tolerate those who incite others to violence. And hate speech that targets individuals on the basis of their race, religion, ethnicity, gender, or sexual orientation is reprehensible. It is an unfortunate fact that these issues are both growing challenges that the international community must confront together. And we must also grapple with the issue of anonymous speech. Those who use the internet to recruit terrorists or distribute stolen intellectual property cannot divorce their online actions from their real world identities. But these challenges must not become an excuse for governments to systematically violate the rights and privacy of those who use the internet for peaceful political purposes.

The internet can help bridge divides between people of different faiths. As we look for ways to expand dialogue, the internet holds out such tremendous promise.

Some nations, however, have co-opted the internet as a tool to target and silence people of faith. Last year, for example, in Saudi Arabia, a man spent months in prison for blogging about Christianity. And a Harvard study found that the Saudi government blocked many web pages about Hinduism, Judaism, Christianity, and even Islam. Countries including Vietnam and China employed similar tactics to restrict access to religious information.Just as these technologies must not be used to punish peaceful political speech, they must also not be used to persecute or silence religious minorities.

Now, we have every reason to be hopeful about what people can accomplish when they leverage communication networks and connection technologies to achieve progress. But make no mistake – some are and will continue to use global information networks for darker purposes. Violent extremists, criminal cartels, sexual predators, and authoritarian governments all seek to exploit these global networks. As we work to advance freedoms, we must also work against those who use communication networks as tools of disruption and fear.

States, terrorists, and those who would act as their proxies must know that the United States will protect our networks. Those who disrupt the free flow of information in our society or any other pose a threat to our economy, our government, and our civil society. Countries or individuals that engage in cyber attacks should face consequences and international condemnation.

The freedom to connect is like the freedom of assembly, only in cyberspace. It allows individuals to get online, come together, and hopefully cooperate.

The United States is committed to devoting the diplomatic, economic, and technological resources necessary to advance these freedoms. And as the birthplace for so many of these technologies, including the internet itself, we have a responsibility to see them used for good.

I'm proud that the state department is already working in more than 40 countries to help individuals silenced by oppressive governments. We are making this issue a priority at the United Nations as well, and we're including internet freedom as a component in the first resolution we introduced after returning to the UN Human Rights Council.

We are also supporting the development of new tools that enable citizens to exercise their rights of free expression by circumventing politically motivated censorship. Both the American people and nations that censor the internet should understand that our government is committed to helping promote internet freedom.

We feel strongly that principles like information freedom aren't just good policy, not just somehow connected to our national values, but they are universal and they're also good for business.

Countries that censor news and information must recognize that from an economic standpoint, there is no distinction between censoring political speech and commercial speech.

Increasingly, US companies are making the issue of internet and information freedom a greater consideration in their business decisions. I hope that their competitors and foreign governments will pay close attention to this trend. The most recent situation involving Google has attracted a great deal of interest. And we look to the Chinese authorities to conduct a thorough review of the cyber intrusions that led Google to make its announcement. And we also look for that investigation and its results to be transparent.

The internet has already been a source of tremendous progress in China, and it is fabulous. There are so many people in China now online. But countries that restrict free access to information or violate the basic rights of internet users risk walling themselves off from the progress of the next century. Now, the US and China have different views on this issue, and we intend to address those differences candidly and consistently in the context of our positive, co-operative, and comprehensive relationship.

We need to work toward a world in which access to networks and information brings people closer together and expands the definition of the global community. Given the magnitude of the challenges we're facing, we need people around the world to pool their knowledge and creativity to help rebuild the global economy, to protect our environment, to defeat violent extremism, and build a future in which every human being can live up to and realise his or her God-given potential.

• This is an edited extract of a speech by US secretary of state Hillary Clinton on internet freedom, delivered on 21 January 2010 at the Newseum, Washington DC