Tor (network)

Tor is a free overlay network that helps people communicate anonymously online. It uses free and open-source software run by thousands of volunteers around the world. These volunteers operate relays, which are special servers that help route internet traffic.

When someone uses Tor, their internet activity is sent through random paths using these relays. This method is called onion routing. It makes it very hard for anyone to figure out where the traffic came from or where it is going, protecting the user's location and privacy.

By hiding a user's location and activity, Tor helps protect freedom of speech and allows people to communicate confidentially, even in places where network surveillance or traffic analysis might otherwise monitor what they do online.

History

The idea behind Tor, called onion routing, was created in the mid-1990s by scientists at the United States Naval Research Laboratory. They made it to keep important messages safe online.

In 2002, the first version of Tor was launched, and in 2004, the code was made free for everyone to use. A group called The Tor Project was started in 2006 to keep working on Tor. Over time, some problems with Tor were found, and scientists study these to make it better. In 2024, Tor joined with the Tails operating system.

Usage

Further information: Dark web

Tor helps people browse the internet, chat, and send messages without others knowing who they are. Many different kinds of people use Tor, both for good reasons and for bad. Some use it to protect their privacy, while others use it for illegal activities.

Tor is not a perfect solution for hiding everything online, but it makes it harder for websites to follow what a person is doing. Even though some people use Tor for bad things, many others use it to stay safe, share important information, or avoid being watched by others online.

Operation

Tor helps keep people's identities and online activities private. It does this by sending information through a series of computers around the world run by volunteers. Each computer in the path adds a layer of encryption, like an onion, so no one can see who is sending or receiving the information.

People can use Tor to make their browsing, chats, and other online activities harder to trace. Tor works with many types of online services and can even help websites stay hidden from watchers. These hidden websites use special addresses and can be reached only through Tor, keeping both the user and the site anonymous.

Attacks and limitations

Tor has some limits and can be attacked in different ways. While many of these issues are small or get fixed quickly, some are more important.

One big idea is that Tor tries to hide who you are by making your internet traffic look like it comes from many different places. But if someone can watch both where your traffic starts and where it ends, they might figure out who you are. This is hard for big groups to do, but sometimes police can watch a person they suspect and see if that person’s internet use matches what Tor is doing at the same time.

Tor also depends on a few special computers called directory authority nodes to help it work. If most of these special computers were controlled by someone bad, they could change how Tor works. There have also been times when attacks tried to stop these computers from talking to each other, but these attacks were noticed.

Some websites can tell if you are using Tor and might not let you use their services or might give you fewer choices. This is because all Tor users share a smaller number of exit points, so sometimes a website might think you are doing something bad because someone else using Tor did it.

There have been times when bad people tried to trick Tor users by changing how Tor works, but these problems were fixed.

When using Tor, some apps might still give away clues about your computer, like screen size or language settings. This can help someone figure out who you are. Some versions of Tor, like the Tor Browser, try to hide these clues.

Tor also can’t hide what happens after your traffic leaves Tor, so if a website doesn’t use extra safety measures, someone watching could see your username or password. Some bad people have used this to steal information.

There have been times when older versions of Tor had problems that let people learn more about who was using Tor. These problems were fixed, but they showed that it’s important to keep software up to date.

Software

See also: The Tor Project § Tools, and Guardian Project (software) § Projects

The main program for Tor is mostly written in a computer language called C. In 2020, work began on rewriting it in a different language called Rust. This new version, named Arti, was announced to the public in July 2021.

The Tor Browser is a special web browser that lets people use the Tor network. It was first created in 2008 and is based on a popular browser called Mozilla Firefox. The Tor Browser includes extra tools to help keep users private online. It can be used on many types of computers and devices. The browser automatically deletes some personal information after use to help protect privacy. It also offers different security levels to block certain features that might make a computer less safe.

Reception, impact, and legislation

Tor has been praised for helping people keep their information private online. It is especially useful for activists in places where the government watches the internet closely, for regular people who want to hide their browsing from companies or spies, and for anyone who needs to talk to others without being followed.

The project began with support from the U.S. government and still receives some funding from them, as well as from other groups that care about freedom of speech online. Some people worry that because of this funding, the U.S. government might be able to control Tor or see who uses it. However, Tor’s leaders say they do not work with any government to share users’ information.

Critics say Tor is not always perfectly safe. Sometimes law enforcement can find and arrest people who make mistakes while using Tor. Overall, though, Tor remains a strong tool for protecting privacy on the internet.

Improved security

Tor has made changes to fix past problems and improve safety. It is important for users to follow the instructions on the Tor Project website to use the Tor browser correctly. If not used properly, Tor might not keep users safe. For example, Tor only protects traffic that goes through the Tor browser. Users should use websites that start with HTTPS, avoid using certain file-sharing methods with Tor, and not enable extra browser features.

Even though some agencies have claimed they could find out who is using Tor, this has not happened as often as they said. For example, in 2016, the FBI could not find the person who broke into an email account connected to a worker for Hillary Clinton.

The best way for authorities to find out who is using Tor is by using special computers called poisoned nodes or by hoping users make mistakes. For example, if someone downloads a video using Tor and then opens it on a regular internet connection, their real location might be exposed.

Odds of detection

When used correctly, the chance of being found out while using Tor is very low. One way this can happen is if an attacker uses special computers to watch traffic, but this is difficult and expensive. The chance of this happening to a user is very small, about one in two million.

Tor does not protect against certain types of attacks where an attacker watches both the user's computer and the destination server. This method was used by German authorities to find users connected to Boystown.