Based on that research, it offers a technology that bounces internet users and websites traffic through 'relays' run by thousands of volunteers around the world, making it extremely hard for anyone to identify the source of the information or the location of the user.
Its software package – the Tor browser bundle – can be downloaded and used to take advantage of that technology, with a separate version available for Android smartphones.
Who uses TOR?
The Tor project team say its users fall into four main groups: normal people who want to keep their internet activities private from websites and advertisers; those concerned about cyberspying; and users evading censorship in certain parts of the world.
Tor notes that its technology is also used by military professionals – the US navy is still a key user – as well as activists and journalists in countries with strict censorship of media and the internet. Campaigning body Reporters Without Borders advises journalists to use Tor, for example.
Tor also cites bloggers, business executives, IT professionals and law enforcement officers as key users, with the latter including police needing to mask their IP addresses when working undercover online, or investigating 'questionable web sites and services'.
For more mainstream users, it could mean running Tor so that your children's location can't be identified when they are online, or could mean a political activist in China, Russia or Syria could protect their identity.
After the NSA surveillance revelations in 2013, a new wave of users joined the service. Between 19 August and 27 August alone the number of people using Tor more than doubled to 2.25 million, according to Tor's own figures, before peaking at nearly 6 million in mid-September. It has since slipped back to just over 4 million.
We strongly recommend downloading the TOR browser exclusively from the official Tor Project website.Download TOR