How safe is VMware's hypervisor?

CanSecWest VMware researcher Oded Horovitz got an earful when he told a group of security buffs his company's virtualization software was theoretically impenetrable. Speaking at the CanSecWest conference in Vancouver, his hour-long presentation, titled Virtually Secure, included a slide titled "VM Escape" that carried the following bullet point:

"Though impossible by design, the hypervisor can still have implementation vulnerabilities."

It was more than some attendees could bear.

"And the Titanic was unsinkable," Mike Poor, a senior security analyst for IntelGuardians shot back. Other attendees complained that security increasingly looked like an afterthought as VMware continued to add new bells and whistles to its Workstation and ESX Server products - many from third party companies.

"I take strong issue with your saying 'trust the hypervisor' when you're expanding it to run other people's APIs," one attendee, who asked not to be identified, told Horovitz immediately following his talk.

The topic is of supreme importance to the future of security. Researchers already depend on VMware Player and Workstation as a means of protecting their machines when analyzing Trojans and other types of malware. And increasingly, large companies are considering virtualization as a means of insulating their servers against rootkits and other types of malware that can burrow into the deepest recesses of their machines and remain there undetected for months or years.

VMware is increasingly holding out ESX as a safer alternative for enterprise computing. It provides a hypervisor that runs directly on top of the hardware and in turn allows one or more "guest" operating systems to run above. VMware says the hypervisor provides an additional layer of protection that is much more resistant to malware than various operation systems. What's more, the hypervisor can sit below the OSes and perform various tasks such as malware detection and patch monitoring.

If the dissenters sound skeptical that hypervisor is impervious, they have their reasons. Poor said his firm received $1.2m from the Department of Homeland Security to look for ways attackers can penetrate hypervisors and ways security researchers can detect and prevent such escapes. Because the two years worth of research is under lock and key, Poor could only say: "We were successful in all three."

And it was only last month that researchers from Core Security Technologies found a bug in VMware's desktop virtualization applications that in some cases allowed attackers to take complete control of the underlying PC. While the vulnerability didn't affect the hypervisor in ESX, it did demonstrate that the protective layer in related VMware products wasn't always as secure as some researchers assumed.

"I'm thrilled they're taking security seriously," Poor said in an interview. "I'm thrilled they have people like Oded on board, and I'm thrilled that the community has brought security to the forefront of VMware's developers. I'm opposed to blindly trusting anything." ®