A tweaked version of the Firefox browser that makes web browsing anonymous has been released by a group of privacy-minded coders.

The Torpark browser causes a computer's IP address to appear to change every few minutes. IP addresses – numeric identifiers given to computers on the internet – can be used along with other data to potentially track down a user.

Torpark's creators, a group of computer security gurus and privacy experts named Hactivismo, said they want to expand privacy rights on the web as new technologies increasingly collect online data.

The browser is a modified version of Portable Firefox, an optimised version of the browser that can run off a USB memory stick on a PC. It uses encryption to send data over the Onion Router, a worldwide network of servers nicknamed 'Tor' set up to transfer data to one another in a random, obscure fashion.

One minor downside is that surfing with Torpark is slower than with a typical browser over the same connection.

Torpark also warns that data sent from the last Tor server to the website is encrypted. Since only the user's connection is anonymous, Torpark advises that sensitive data such as username and passwords should only be used when the browser displays a golden padlock, a sign that a website is using encryption.

Torpark's user interface appears similar to Firefox with a few changes. It shows the current IP address that would be seen by sites in the lower righthand corner, and features a special 'Flush Tor' button to reset a new, random server connection.

A test of Torpark using a computer in London employed IP addresses of servers registered in Berlin and Madison, Wisconsin.