When you think of the internet, what do think of? For many people, the internet conjures thoughts of familiar sites such as Google, Facebook, or an email client. But like any system, the internet exists in several layers. The top most layer can be said to be the visible layer, frequented by webcrawlers indexing the web so that search engines can produce the results users seek. Beneath that layer lies the so-called deep web, typically consisting of internal web pages or databases not easily indexed by web spiders. Beyond that lies the dark web, accessible only through special browsers like Tor.

Tor, which was originally shorthand for “the onion router”, was first developed by the US government. It is now developed and maintained by the open-source Tor Project. On one level, Tor operates like any other browser. There is a search bar where users enter web addresses, and similar functionality to other modern web browsers. However, Tor offers a few unique features, the most important of which is how network traffic is sent between the browser and the website server.

Unlike a regular browser, where traffic is routed in the most efficient manner to the website server, hopping through cyberspace in plain view, the Tor browser obfuscates the origin of the request by routing through specially designated Tor nodes. These nodes are servers operated by volunteers around the world. The nature of how the data is routed makes it extremely difficult to trace the originating request at a website, giving a substantial level of anonymity to users.

Through use of Tor nodes, individuals can also host websites only accessible via Tor. These sites, also called hidden sites or onion sites because the web addresses end in .onion, are invisible to webcrawlers and can typically be accessed only if you know the full web address. While frequently associated with criminal activities, like the now-defunct Silk Road drug market, hidden sites can also serve as platforms for journalists and political activism.

As with many aspects of technology, Tor is a double edged sword. It can be used to protect users’ privacy and allow political dissidents a way to communicate securely, but it also serves as a platform to further the aims of criminals. But since the encryption that secures our everyday activities on the internet is the same as that used by Tor, it would be very difficult to preserve the good while rooting out the bad.