An international group of computer security experts and human rights workers has released an anonymous, fully portable web browser based on Mozilla Firefox.

The Torpark browser comes pre-configured and requires no installation. It runs off a USB memory stick, and claims to leave no tracks behind on the browser or computer.

Hacktivismo, the organisation behind the project, said that Torpark is a highly modified variant of Portable Firefox that uses The Onion Router (Tor) network to create an anonymous connection between the user and the websites being visited.

Typically, when a user logs onto the internet, a unique IP address is assigned to manage the computer's identity. Each website the user visits can see and log the user's IP address.

Hostile governments and data thieves can monitor this interaction to correlate activity and pinpoint a user's identity.

But the Tor network causes the IP address seen by the website to change every few minutes to frustrate eavesdropping and mask the requesting source.

Furthermore, the data passing from the user's computer into the Tor network is encrypted.

Therefore, the user's ISP cannot see the information passing through the Torpark browser, such as the websites visited, or posts the user might have made to a forum. The ISP can only see an encrypted connection to the Tor network.

"We live in a time where acquisition technologies are cherry picking and collating every aspect of our online lives," said Hacktivismo founder Oxblood Ruffin.

"Torpark continues Hacktivismo's commitment to expanding privacy rights on the internet. And the best thing is, it's free. No one should have to pay for basic human rights, especially the right of privacy."

Hacktivismo acknowledges that there are limitations to the anonymity of Tor. Torpark makes the user's connection anonymous but not the data.

Data travelling between the client and the Tor network is encrypted, but the data between the Tor network and websites is unencrypted.

Therefore, the user should not use his/her username or password on websites that do not offer a secure login and session.