What is Internet Censorship, and How Does It Work?

Internet censorship is a contentious topic. While most people agree that some digital content should be off limits, there’s little agreement about exactly what should be restricted or who has the right to decide.

Internet censorship varies greatly from country to country. In Iceland, there are very few restrictions online, whereas in China people struggle to access any information that could be perceived as critical of the government.

Broadly speaking, Internet censorship is when someone controls what others can see and do online. It can take a variety of forms and be implemented by a wide range of institutions.

It is also subjective: what some consider to be censorship may be considered by others as ethical behavior.

Schools, for example, may block access to age-inappropriate content. However, they might also block access to news websites and other important sources of information because they do not conform with the school’s religious views.

Governments often justify internet censorship by arguing that it helps prevent the spread of misinformation or harmful content. However, these justifications are often thinly veiled attempts at maintaining social control.

Widespread internet censorship can have a devastating impact on freedom of expression and other fundamental human rights. It can make it difficult to voice opposition, learn about a government’s failings, or organize political opposition.

Internet censorship can be implemented by software developers, app store managers, internet service providers (ISP), or by those working on a country’s internet infrastructure.

In this article, we’ll be mainly talking about government-mandated internet censorship.

What Is the Purpose of Internet Censorship?

Internet restrictions are often imposed to prevent the spread of illegal content. However, governments, social media platforms, and other organizations can abuse their power and censor content that’s critical of them.

We’ve repeatedly documented governments blocking access to social media sites and other content online during periods of political instability, elections, and conflict. In response, citizens regularly turn to VPNs to retain access to the blocked content.

Internet censorship can be used to silence the opposition during elections. It can cover up human rights abuses during conflicts, and even disrupt attempts to coordinate relief efforts after natural disasters.

Internet censorship is fundamentally about controlling what people can see and say online. That means it’s often about maintaining control, rather than keeping people safe.

Who Is Responsible for Internet Censorship?

Any organization that provides access to information online also has the power to censor it.

An institution such as a school or college may censor internet content because it is considered unsuitable for young people.

Social media sites and search engines sometimes remove content for violating their own terms and conditions or because of government requests.

Your Internet Service Provider (ISP) might be required to block content following government orders. If the ISP doesn’t comply, it risks losing its license to operate in that country.

In some countries, government agencies use sophisticated technology to monitor and block access to specific websites, social media posts, and apps.

The Global Impact of Online Censorship

Online censorship has both positive and negative effects.

Widespread internet censorship can also have negative impacts for millions of people.

There are a number of techniques that may be used to censor the internet. Each type of internet censorship requires specific technology and has its own potential limitations.

IP Blocking

Every web server has an IP address. IP blocking is a technique where censors generate a blocklist of known IP addresses and reset any connections attempting to connect to them. IP blocking can be used to block websites from entire countries or regions.

This is a relatively rudimentary type of censorship and it doesn’t require particularly sophisticated technology. However, it can cause overblocking, as several sites may share an IP address.

To get around IP blocking, a web proxy or a VPN can be used, if these services are not also blocked.

DNS Tampering

The domain name system (DNS) is used to convert a website address into the IP address of the server where it’s hosted. It is one of the first steps that happens when trying to access a website.

State agencies and ISPs can block access to websites or divert people to an alternative website by interfering with these DNS servers.

Some networks in China use a technique called “DNS mangling”, which returns a false response if someone tries to access a blocked website. This can also be referred to as “DNS lying.”

There is also “DNS cache poisoning”, which interferes with the response sent by a legitimate DNS server.

Although HTTPS encrypts much of your connection requests, DNS is largely unencrypted. This allows censors to view what website you’re trying to access and block the connection.

DNS tampering attacks like these can be circumvented. It’s possible to use an alternative public DNS server that is unaffected by government or ISP censorship, or set up a Smart DNS connection.

You can use free tools to check which DNS server your device is using, and change it if necessary.

Deep Packet Inspection (DPI)

Data travels across the internet in small sections called packets. Deep packet inspection (DPI) is a technique where the contents of these packets are studied as they travel across the internet.

When content is unencrypted, it’s possible to monitor all the traffic in transit. This allows censors to easily monitor and interfere with peoples’ connections.

If content is encrypted, DPI can still see the metadata, which reveals the type of traffic, the IP address, the amount of data transferred, and the date and time of that transfer. That can sometimes be enough to identify banned activity and block the connection.

DPI can be used to block VPN traffic, for example, unless VPN obfuscation is used to disguise it.

To help protect yourself against DPI, you can use a VPN, or try adjusting your network settings (the TCP/IP stack’s MTU/MSS) to reduce the amount of text contained in each packet.

URL Filtering

For censors, the problem with techniques such as DNS tampering and IP blocking is that you need to know which IP addresses or domains you want to block. There are too many to draw up a comprehensive list, and new sites are launching all the time.

URL filtering works by checking website addresses for banned keywords. If they are found, the connection is reset.

Censorship techniques based on keywords are particularly prone to overblocking. They may not be able to differentiate between pornography and sex education content, or between sites that promote alcohol abuse and sites that help people with recovery.

The “Scunthorpe problem” is so called because stories about the UK town have sometimes been blocked because the town name contains an offensive word.

Using a HTTPS connection, the censors can see the web domains you visit but not the individual pages you view. Censors have the option to block the entire domain or nothing on it, in that case. In China, entire blogging domains such as WordPress are blocked.

Search Engine Censorship

An alternative approach is to prevent search engines from including web sites in their search results in the first place.

Governments can exert pressure on search engines to remove results they don’t want people to see. For some years, Google worked with the Chinese government, providing a Chinese search engine with some results censored at the government’s request. Google withdrew from China in 2010 and its international search engine is now blocked there.

In Europe, Google blocks illegal content to comply with relevant domestic and international laws. It also allows users to request their information be removed from the search engine following a 2014 ruling by the Court of Justice of the European Union (CJEU). This is often referred to as the right to be forgotten.

Internet Throttling

Throttling is a technique where an internet connection is slowed down. If a connection is slowed enough, it can make the user’s device time out and drop the connection entirely. Internet throttling is sometimes called traffic shaping.

Governments in India, Venezuela and Jordan have all throttled internet speeds during periods of political upheaval. At times, they have targeted specific websites, while at others they have throttled all internet traffic in a particular region.

It has been often used in the past by ISPs in the US and Europe to slow down users who are torrenting, so they do not consume too much network bandwidth.

Distributed Denial of Service (DDOS) attacks

A distributed denial of service (DDOS) attack uses lots of devices to flood an internet resource with too much traffic, making it impossible for legitimate visitors to access the server. Often, the devices used for an attack have been compromised and their owners don’t know they’re being exploited.

DDOS attacks were launched by Russia against Ukrainian banks and government sites before the 2022 invasion, and are used in the Philippines against opposition politicians and independent media.

It’s cheap and easy to launch a DDOS attack today, with a 24-hour attack costing only a few hundred dollars.

As a web user, there’s not much you can do if the site you want to access is forced offline. You may be able to look for mirror sites or other places that host the same information, or you might have to wait until access to the site is restored.

Port Number Blacklisting

By blocking certain ports, censors can block entire applications. For example, web access, email, instant messaging, or VPN traffic.

This approach is sometimes used in the workplace to stop unauthorized applications, such as torrenting.

On-Device Software

In some cases, software can be installed on a device to censor the content that can be viewed on it. Most commonly, this is used by parents to protect children and young adults from content that is harmful to them.

In some cases, governments can install software on devices to control the information accessible through them. In May 2009, the Chinese government ordered manufacturers to include censorship software on computers they sold. They later said this was only necessary for computers that would be used in public places like internet cafes.

In 2021, the Lithuanian government found censorship software on a phone made by Chinese company Xiaomi. It censored content and sent data to Chinese authorities.

Internet Blackouts

In extreme cases, countries can turn off the entire internet in a region. These internet blackouts force everyone offline and are often imposed during protests or elections.

In 2019, the government in Sudan restricted access to the internet across the entire country. Following a court case that found the restrictions were unlawful, access to the internet was restored — but only for the one person who challenged the restrictions in court.

Since 2019, we have recorded more than 500 major government-mandated internet shutdowns. These include internet blackouts, as well as social media shutdowns and severe throttling.

In total, these restrictions cost the global economy over $44 billion. In 2022, countries including Russia, Myanmar, Iran, India and Ethiopia all implemented internet shutdowns.

Self-Censorship

In many countries, oppressive regimes encourage people to censor themselves, out of fear of reprisals.

In China, for example, journalists, human rights lawyers, and activists have been detained for their online activities. In Iran, journalist Ruhollah Zam, who founded a site critical of the government, was executed. Vietnam has sentenced a number of independent online journalists to prison terms of between two and 10 years.

With penalties such as these, many people are reluctant to share their true thoughts online, and so are unable to form associations with others who hold the same views.

The Freedom on the Net report provides an annual snapshot of government censorship and internet freedoms worldwide. It ranks countries and considers issues such as barriers to information access, technical filtering of content, and violations of user rights, including surveillance and restrictions on free speech.

Its latest report found that global internet freedom has declined for 12 years in a row, although 26 countries did show improvements.

The report’s methodology gives each country a score out of 100 and ranks them. Only four countries – Canada, Costa Rica, Iceland, and Japan – had no internet controls.

Countries With the Greatest Internet Freedom	Countries With the Least Internet Freedom
1. Iceland	1. China
2. Estonia	2. Myanmar
3. Costa Rica	3. Iran
4. Canada	4. Cuba
5. Taiwan	5. Vietnam
6. United Kingdom	6. Russia
7. Georgia	7. Saudi Arabia
8. Germany	8. Pakistan
9. Japan	9. Uzbekistan
10. Australia	10. Ethiopia

In this section, we give a brief overview of the state of internet censorship in some notable countries worldwide:

Cuba

Cuba is a communist state where independent media is blocked. The government controls the internet infrastructure and it owns the fixed and mobile telecommunications providers. Social media platforms and VPNs are among the sites that have been restricted in recent years.

The reasons for censorship include transmitting false information and content that affects “the identity, integrity and honor of the person”. There is no transparency or oversight and there are many laws restricting online freedom.

Ethiopia

Ethiopia enacted one of the world’s longest internet shutdowns in Tigray, where there is a civil war. Restrictions began in 2020 and, although the government agreed to restore internet access, that didn’t happen for another 2 years.

The restrictions prevented journalists from reporting on the conflict and has hampered attempts to distribute humanitarian aid.

Iceland

Iceland has the most free internet, according to Freedom on the Net. Nevertheless, there are still some restrictions on websites.

The Pirate Bay and the country’s biggest torrent website Deildu are blocked by ISPs because they infringe copyright. The government also requires telecommunications providers to keep user data for six months, including browsing data, for possible use in criminal cases.

India

India is the global leader in internet shutdowns. Shutdowns are carried out in response to civil unrest and protests, and even to stop cheating on school exams.

More than 16,000 websites have been banned and Twitter and YouTube have repeatedly removed content following requests from the government.

Iran

Iran has used internet shutdowns to try to stop protests, and most international websites are blocked. Those who criticize the government are liable to be arrested, which results in self-censorship where others are reluctant to speak out.

International trade sanctions have also prevented many websites from the West being accessible in the country.

Twitter, Facebook, blogging sites, international media, and political opposition websites are among those blocked. LGBT+ content is blocked, and domestic news sites are often blocked for criticizing the government.

Kazakhstan

Kazakhstan throttled and shut down internet access to stop news of protests and the violent government response from spreading. Under Kazakhstan law, the government has the right to shut down communications networks if there is a risk of an emergency.

The National Security Committee can also block content and disrupt networks to prevent crime. The government has control over international internet gateways, and the centralized internet architecture helps the government to carry out surveillance and censorship.

Myanmar

Myanmar has laws that severely restrict internet freedom and that have been used to punish dissent. Journalists have been imprisoned for covering protests and activist Kyaw Min Yu was executed after criticizing the 2021 military coup on social media.

The government has the power to access any information held by telecommunications firms for the vaguely-worded “benefit of the people”.

Soldiers have searched people’s devices on the street for VPNs, threatening arrest.

Nigeria

Nigeria’s government blocked Twitter between June 2021 and January 2022 after Twitter censored a tweet by the president. The tweet appeared to threaten violence against a separatist group and therefore breached Twitter’s rules.

Although the government struggles to systematically block content, the news website Peoples Gazette has at times been blocked on mobile internet services. Public displays of same-sex relationships are illegal, so many LGBT+ people censor themselves online or post anonymously.

Russia

Russia uses censorship extensively to stifle political opposition. The Federal Service for Supervision of Communications, Information Technology and the Mass Media (Roskomnadzor) uses deep packet inspection to block web content.

Facebook, Twitter, and Instagram were blocked completely following the invasion of Ukraine. Facebook’s parent company Meta is considered an “extremist organization”. Independent news sites, including the BBC and Google News, have also been blocked.

As of 2024, there are very few VPN services that still work in Russia. Many popular VPN services have been blocked in an effort to stop people getting around internet restrictions.

United Arab Emirates

United Arab Emirates residents are blocked by ISPs from accessing pornography, gambling sites, and websites that criticize the government. LGBT+, human rights and atheist content is also blocked. Facebook, Google, and Twitter have all received requests from the government to remove content.

The state owns or partly owns the country’s ISPs and its largest mobile operators, and the state also operates a sophisticated surveillance system. The risk of legal action or harassment means people are reluctant to criticize the government or post on LGBT+ issues.

The Great Firewall of China

China has the strictest internet censorship regime in the world, blocking international news websites, independent Chinese news outlets, human rights organizations, and social media sites.

Google Search and some other Google services (including Maps, Translate and Docs) are blocked too. Most VPN services are banned, though there are some VPNs that still work in China.

Chinese companies are forced to remove content that is critical of the ruling party. That includes any discussion of the 1989 Tiananmen Square massacre or the Taiwan independence movement. Other banned topics include religion, the Falun Gong community, LGBT+ issues, women’s rights, and some topics surrounding the Russian invasion of Ukraine.

Tens of thousands of blogs and social media accounts have also been shut down. For more specific information, you can use our tool to check which websites are blocked in China.

China’s censorship program is called the Golden Shield Project. The country has built the world’s most sophisticated censorship apparatus, a combination of technical measures and human labor known as “The Great Firewall of China”.

There are even concerns that Chinese surveillance has expanded globally through the use of Chinese technology abroad.

Internet Censorship In the United States

The US protects free speech under the constitution and there is no systemic government censorship of content. Where censorship happens, it is usually as a result of platform owners such as social media sites enforcing their terms and conditions against hate speech or violence.

There are currently no laws against VPNs in the US. However, law enforcement agencies have been caught conducting widespread surveillance of citizens and visitors without transparency or oversight.

The FBI was found to have conducted improper searches on the communications data of US citizens tens of thousands of times in an October 2019 judgment by the Foreign Intelligence Surveillance Court.

Previously, Edward Snowden revealed in 2013 the National Security Agency (NSA) was collecting domestic call detail records in bulk. In 2015, this was ruled illegal.

The US Customs and Border Protection (CBP) agency searches travelers’ devices and requires them to hand over passwords. Visa applications request email addresses and social media account details for the previous five years.

One of the challenges with internet censorship is working out how much it’s happening, and where. When censorship is used to violate human rights, including the right to free expression and the right to peaceful assembly, governments are unlikely to publicize that.

In addition, many of the technologies and techniques used are designed to avoid detection.

If content has been tampered with, most internet users might not notice. Often, they just might see an error message that looks like a network fault.

There are several organizations working to document internet censorship around the world:

• Since 2012, the Open Observatory of Network Interference (OONI) has been inviting people to run its software to test the blocking of websites and apps. OONI has collected 1583.7 million measurements which it shares as raw data and contextualizes into research reports. China began blocking OONI in July 2023, which will make it hard to gather reliable test data there.
• The Censored Planet Observatory uses automated remote measurement techniques to test access to thousands of websites from vantage points in 221 countries. It complements OONI by bringing additional scale, without the need for volunteers to participate in a measured country.
• The Internet Outage Detection Analysis (IODA) tool uses almost real-time monitoring of internet infrastructure to generate data on outages. It’s useful to researchers, but it doesn’t provide context on why there was an outage.
• Netblocks collects real-time data to detect internet disruption, censorship, and cyber attacks. It publishes news reports highlighting internet restrictions around the world and the events that led the authorities to enforce them.
• At Top10VPN, we conduct our own research, too. We’ve calculated the cost of internet shutdowns, reported on the websites blocked in Russia since the Ukraine invasion and have detailed the websites blocked by UK ISPs.