Oct 26, 2010 15:53 GMT  ·  By

Security researchers from Norman have come accross a drive-by download attack exploiting an unpatched Firefox vulnerability in order to infect users with a new trojan.

The attack was launched from the Nobel Peace Prize website, which appears to have been compromised and had rogue code injected into its pages.

According to Norman, the exploit used targeted a previously unknown vulnerability affecting versions 3.5 and 3.6 of the Mozilla Firefox browser.

The antivirus company doesn't mention wether this attack was instrumented with an exploit kit targeting vulnerabilities in multiple applications, as it is normally the case, or if it was only aimed at Firefox users.

The second scenario would be somewhat unusual, because Mozilla Firefox has not been commonly targeted in drive-by downloads for quite some time now, even though it is the second most used browser in the world after Internet Explorer.

This is because more widespread software like Java, Adobe Reader or Flash Player are usually more attractive targets for cybercriminals.

Norman reports that successful exploitation of the Firefox zero-day flaw, led to the installation of a new trojan the company dubbed Belmoo.

According to researcher, the trojan installer was created on Sunday and drops a file called symantec.exe in the %WINDOWS%\temp folder.

The file name was clearly chosen to mislead users, and so is the "Microsoft Windows Update" name used for the start-up registry entries created under HKCU\Software\Microsoft\Windows\CurrentVersion\Run and HKLM\Software\Microsoft\Windows\CurrentVersion\Run.

After installation, the trojan tries to establish connections with nobel.usagov.mooo.com and update.microsoft.com over port 80 (HTTP).

It's not yet clear why it queries the microsoft.com host and the first address is not currently used for anything.

The malware also tries to connect to two different addresses pointing to a server in Taiwan. It tries different ports and if any attempt is successful, it opens a local shell.

An attacker located at the other end can then use it to execute commands with the privileges of the current user.