The Web browser, called "Torpark," is a modified version of Portable Firefox. Released last week, it can be run directly from a USB drive, meaning it can be used on public terminals in cybercafes. It creates an encrypted connection to the TOR (The Onion Router) network, which supplies a succession of different IP addresses.
"Torpark causes the IP address seen by the Web site to change every few minutes, to frustrate eavesdropping and mask the requesting source,"said in a statement.
For example, a user could be in London and Web sites would see an IP address from a university in Germany, or other addresses belonging to the TOR network.
Hacktivismo operates under the aegis of the influential group the Cult of the Dead Cow. Developers said the browser is different from other anonymous browsers, such as Anonymizer or SecretSurfer, in that it doesn't cost anything and is small and portable.
Torpark uses English by default, but includes language packs for Arabic, German, French and simplified Chinese. More than 30 other language packs are available via links built into the browser, which is available here.
The Torpark site was available intermittently this week, because of heavy download traffic, developers said.
The browser encrypts data sent to the TOR network, but data isn't encrypted between TOR and the destination Web site, Hacktivismo cautioned. "Therefore, the user should not use his or her user name or password on Web sites that do not offer a secure login and session," the group stated.
The browser session is somewhat slower than with an unmodified browser, testers have reported. The browser resembles, but displays the IP address being used at the time, and includes a button for resetting the server connection.
The official launch follows more than a year of development work on Torpark. A sister application called Torbird is also available; it uses the TOR network for e-mail.
Matthew Broersma reported for ZDNet UK from London.