Virtualization's secret security threats

Virtualization's secret security threats

Virtualization can be both a blessing and a curse, serving up improved security while at the same time hiding dangers

Using virtual layers to add security

While virtualization is used commercially to have multiple operating systems run on one machine -- to get more usage from physical servers, to run Windows on Macs, and to easily set up testbed environments -- its origins trace back to a military security need. In fact, the VMware technology that popularized virtualization is a spin-off of US Defense Department-sponsored research done at Stanford University; the military saw early promise in virtual machines to encapsulate networks and desktops from outside threats, resulting in an NSA-created OS called NetTop that in 2001 did for Linux what products such as Parallels Desktop and VMware Desktop do today: provide separate VMs that can't affect each other on one box.

Now the NSA sees virtualization protecting systems in a new layering approach, Simard said. The idea is to have an independent layer handle security, so even if an OS has security flaws, a separate layer that the OS can't compromise handles security threats such as viruses and worms or implements firewalls. Simard said it's inevitable that PC operating systems will have security holes: "The PC platform is a very feature-rich platform, and being feature-rich gets it into trouble."

The NSA, working with General Dynamics and IBM, has developed the first version of this technology, which it calls the High Assurance Platform workstation, for the US Special Operations Command, using VMware, Novell SuSE Linux, and Red Hat Linux, Simard said.

"I believe strongly in doing antivirus and firewalling in isolation outside the OS," said AMD's McDowell. But Simard is concerned that this layered approach could compromise security if poorly implemented in commercial systems. The reason: If the security layer is compromised, such as through poor design, then an intruder now has access to all the VMs on the system. McDowell agreed with that concern, saying that such a layered approach can't replace security at the OS and network -- instead it must supplement those components' security. He also noted that applications are the most common route for vulnerabilities to find their way into an OS, so they too need to have their own protection mechanisms.

A related concern is the hypervisor, the root layer that manages the VMs. If compromised, it could expose everything on the system. But McDowell is least worried about this scenario: "Hypervisors are very hard to write, and there are just three of them -- Xen, Microsoft, and VMware" -- so there's not broad expertise for hackers to tap into, he said.

The leapfrog effect

Citrix's Roemer noted that the NSA's risk examples are on the extreme side. "They're onto something there, but a lot of their needs greatly exceed that of other organizations, he said.

The NSA's Simard agreed, but noted that there's a leapfrog effect, in which the NSA and other government agencies sometimes are the first to come across a threat, and feed that experience to commercial companies to help them improve their products. The commercial companies take the issue a step further and end up having better options than the government, which then pushes the envelope in its usage and discovers new issues.

He sees this being very true in the virtualization world, where the feds were the first to see the technology as a security aid and then, more recently, as a new potential threat vector. "Hopefully, industry will learn from our worries," Simard said.

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