Also known as Morcut, the malicious rootkit--spread via an installer that's disguised as an Adobe Flash Player installer--was first discovered last month by antivirus vendor Kaspersky, which found it targeting Apple OS X systems. But the installer, which is a Java archive (a.k.a. JAR) file--dubbed Maljava by Symantec--that claims to have been signed by VeriSign, also includes the ability to infect Windows machines with the Crisis rootkit.

"The JAR file contains two executable files for both Mac and Windows. It checks the compromised computer's [operating system] and drops the suitable executable file," said Takashi Katsuki, a software engineer at Symantec Security Response, in a blog post. "Both these executable files open a back door on the compromised computer."

[ Security researchers, take note: Google Ups Bug Bounties Amid Booming Exploit Market. ]

Crisis includes multiple Windows-only features and propagation techniques. Notably, on Windows systems, "the threat uses three methods to spread itself: one is to copy itself and an autorun.inf file to a removable disk drive, another is to sneak onto a VMware virtual machine, and the final method is to drop modules onto a Windows Mobile device," said Katsuki.

But he emphasized that the malware doesn't spread using a flaw in the VMware virtual machine software. Rather, "it takes advantage of an attribute of all virtualization software: namely, that the virtual machine is simply a file or series of files on the disk of the host machine," he said. "These files can usually be directly manipulated or mounted, even when the virtual machine is not running."

According to Symantec, this is the first-known example malware that attempts to propagate via a virtual machine. "Many threats will terminate themselves when they find a virtual machine monitoring application, such as VMware, to avoid being analyzed, so this may be the next leap forward for malware authors," said Katsuki.

But as noted, the malware can spread not only via Windows, Apple OS X, and virtual machines, but also by dropping attack modules onto any Windows Mobile devices that are connected to a Windows PC. To do so, Crisis employs the Windows remote application programming interface (RAPI), which doesn't work on Android or iPhone devices. But Symantec said that while it's seen this capability in the malware, it has yet to recover any of the actual Windows Mobile attack modules.

The revelations over the additional Crisis capabilities reinforce that the malware--which offers spyware that can capture keystrokes in browsers and instant messaging clients, and which uses a rootkit that can survive reboots--has been professionally designed, apparently to steal people's personal financial information.

Interestingly, according to Internet discussion boards, the malware may have started life as the Remote Control System, which is information security software developed and sold by the Italian HackingTeam group. According to the company's website, the software is only sold to law enforcement and government agencies.

But the malware appears to have been at least repackaged for sale on hacker forums, according to a blog post from researcher Sergey Golovanov at Kaspersky Lab.

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