Commonly known as the “onion router,” Tor Project is a free software that allows users to browse the Internet anonymously. By defending against traffic analysis—a type of Internet surveillance—Tor aims to protect its users’ privacy and anonymity on the web.

Tor works by creating a distributed, anonymous network.

“The idea is similar to using a twisty, hard-to-follow route in order to throw off somebody who is tailing you—and then periodically erasing your footprints,” Tor’s website explains.

Tor builds circuits of encrypted connections by using many connected relays on a network, such that no single connection can be used to pinpoint a user’s location. Without the full information, each relay knows only where data packets have come from or where they are going, and the user’s Internet protocol (IP) address is never revealed to any website. By sending communications around a distributed network of servers run by volunteers around the world, Tor helps reduce the risk of traffic analysis.  

Under the condition of characteristic anonymity, a Tor core developer came to speak at McGill’s Cultural Industries (COMS: 541) class during Fall 2016.

"You can’t be anonymous alone,” he said. “Anonymity is strengthened by its numbers.”

The many relays around the world help users remain anonymous. In this way, Tor users will become even more secure the more people use the software.

Tor is often used in countries where access is limited due to censorship or other restraints, and thus functions as a vessel for users to reach otherwise blocked content.

“Journalists use Tor to communicate more safely with whistleblowers and dissidents,” Tor’s website explains. “Non-governmental organizations (NGOs) use Tor to allow their workers to connect to their home website while they're in a foreign country, without notifying everybody nearby that they're working with that organization.”

Tor was first created by the United States Naval Research Laboratory almost 20 years ago. Today, there are estimated to be nearly two million users, although it is hard to measure due to the inherent anonymity of the software. The U.S. Navy still uses Tor for open source intelligence gathering and anonymous communications while in the field. Tor is also used for security during sting operations or to prevent websites from seeing government IP addresses in their web logs.

As a result of Tor’s privacy capabilities and ability to mask a website’s location, online black markets are also often formed.

While Tor helps users remain anonymous, it is important to still exercise precaution on the Internet even while using Tor. Almost all communications over the Internet are sent in the form of data packets. Data packets consist of the packet header, which contains information—such as source, destination, and size—and the packet payload, containing the actual data.

“Even if you encrypt the data payload of your communications, traffic analysis still reveals a great deal about what you’re doing and, possibly, what you’re saying,” Tor’s website cautions.

Tor prevents observers from learning what sites a user visits and prevents the sites from learning their actual physical location. However, it does not defend against end-to-end attacks—where statistical analysis is used on traffic coming out of the user’s  computer and into the destination computer to determine if they are part of the same circuit.

Although Tor protects anonymity, it is not foolproof. In fact, in 2009, a McGill student was put on academic probation for editing a professor’s Wikipedia page on McGill’s Virtual Private Network (VPN). IP addresses on a network are managed by a central computer called a router, which forwards data packets between computer networks.

“In the case of McGill networks, this router is owned by McGill,” a 2009 McGill Daily article explained.

Now, IP addresses serve as identifiers and location addresses so when students log into McGill’s VPN with their McGill ID, their identity is revealed and anonymity is no longer a possibility.

In the absence of McGill’s VPN, consider Tor for improved security. As a free and open source software, Tor is a perfect example of human collaboration and innovation, and first and foremost promotes and helps protect personal privacy.