The Infostealer.Snifula, which is based on cross-platform component object models (XPCOMs) that developers use to create extensions for the Firefox browser, installs malicious Trojans that are loaded at start-up. The Trojan captures contents of form submission events including passwords and forwards them to its main process where it is sent to the remote attacker.

Symantec Corp. security response engineer, Candid Wuest said the exploits, which commonly attack Internet Explorer's browser helper objects (BHOs), began attacking Mozilla browsers in March this year with Javascript-based JS.Ffsniff by using the XPConnect Java interface that allows transparent access to XPCOM objects.

"When an infected user submits a Web form on a Web site, [JS.Ffsniff] will parse the site and steal all information that is submitted by the Web form, including passwords," Wuest said. "The JS.Ffsniff script then sends this information to a predefined e-mail address using XPCOM objects."

Joji Hamada, Symantec senior security response manager, said the exploit has had a limited impact locally and recommended downloads from trusted sites only.

"Our intelligence indicates the threat has been noticed in Australia; however, the impact of the attack overall is minimal at this stage," Hamada said. "To protect themselves from this type of threats, users should ensure they only download software from reputable, trusted sites."