On March 20th, we here at Sana labs discovered an in-the-wild rootkit and Trojan that has been actively infecting machines since about the 16th of March. This kernel level rootkit was designed to stealth a Trojan that has some pretty scary capabilities. First, the Trojan can survive reboot and does not run as a separate process. Second, it can discover passwords used previously on a machine, so it does not need to log keystrokes. And third, since the Trojan is hidden by the rootkit, end users cannot see the Trojan on their disk.
This Trojan and rootkit was found during the investigation of an in-the-wild worm, named Win32.Alcra. This worm, if not stopped, attempted to contact various websites and download additional payloads. On one of these websites was the installer for this rootkit and Trojan. Once these components were silently installed on a machine, the Trojan invisibly starts communicating to yet another web server located in Russia. This web server acts as the repository for the stolen usernames and passwords.
One of the sites is still actively infecting machines. It attempts to download several pieces of Spyware, Adware, and Trojans, in addition to the rootkit. The rootkit has two pieces: the first piece is a device driver named 'zopenssld.sys', and a DLL named 'zopenssl.dll'. The device driver appears to cloak any file named 'zopenssld.sys' or 'zopenssl.dll' regardless of where they reside, though the malicious versions are located in the System32 folder.
While the DLL was invisible on the file system, it is visible as an injected DLL in many running processes. Since zopenssl.dll registers itself as a Winlogon.exe extension and does not run as a process, most users would never see it, and it can survive even in safe mode.
The Trojan appears not to be active at all times, but it does wake up and start communicating when it sees a user browsing to a website that requires authentication. To view it in action, a virtual machine was infected with the rootkit and Trojan, and then the user browsed to http://bankofamerica.com
, and entered a fake username and password. All of the network traffic was recorded, and after ending the web browser session, the Trojan communication became apparent.
After further investigation, it was determined that this Malware was sending information to a web server located in Russia. Ironically, this web server was not secured, and any user browsing the site could view the information that was being stolen.
According to the dates on this web server, it has been active since at least the 16th of March. The oldest stolen data observed was from the 19th of March. Based on the sheer amount of data that has been stolen, the infection has been more than tripling in size every day.
Posted by Jeremy on March 21, 2006 09:54 AM