With that information, the Trojan creates a new account under the name "Maestro" on the infected computer. It then "scrapes information from the registry, from the so-called Protected Storage area used by IE to store passwords, and from Firefox's own password storage, and tries to pass the stolen information onward, once per minute," Brandt added.

The Web domain intended to receive the stolen data has already been shut down, but code inside the malware revealed the author's name and email address, which led Webroot to a Facebook page for a hacker based in Iran who provides a free keylogger creator tool targeting users of .

Webroot can easily identify and remove the Trojan from infected machines, it says. To fix the modified Firefox file, users should download the latest Firefox installer and install it over the existing installation. No bookmarks or add-ons will be lost in the process, Brandt said.

How to Make Firefox Forget

Mozilla's Firefox ranks second in global browser market share, according to with 23 percent of the browser market in September. The first of Firefox 4 for Android phones just debuted this week.