The Scary Side of Virtualization

But virtualization does involve risks if best practices aren't followed and adapted to a virtual infrastructure. For example, the hypervisor must be patched just like any other operating system, says KC Condit, senior director of information security at Rent-A-Center.

Security consultants say they've noticed a wide variety of security problems at customer sites.

Lovejoy is seeing malware and cross-site scripting issues that result from poorly constructed virtual machine images, for example. "Commonly, that image will contain malware or have vulnerabilities that can be exploited very easily," she says. "It used to happen once. Now these images are being deployed without end, creating massive headaches for people."

"We're seeing a lot of misconfigured hypervisors," adds RSA's Mulé. He says he often sees poor patch-management practices for virtual machines and the use of easily guessed or default usernames and passwords for virtual machine manager programs that have full access to the hypervisor. In addition, he says, "we sporadically see virtual machine management tools on the wrong side of the firewall."

Using default passwords when creating new virtual servers is very common, says Harold Moss, CTO of cloud security strategy at IBM Security Solutions, and people responsible for administering the new machines don't always change them either. Would-be thieves could dial into a machine, guess the password and have complete control, he explains.

In addition, because virtual machine images are data -- program code stored on a hard disk drive somewhere -- those files must be protected. "You don't want someone walking away with an entire server on a USB drive," says Vauda Jordan, senior security engineer for the Phoenix city government. She says the city uses a combination of physical security, network storage access controls and file integrity monitoring to protect virtual machine images.

The traffic flowing between virtual machines is another area of concern, since firewalls, intrusion-detection and -prevention systems, and other monitoring tools can't tell if the virtual machines are running on the same hardware.

"I've put packet sniffers on virtual servers, and nothing is going in and out of the physical network interface. So, how are those communications happening? And are they over secure channels?" asks Jordan. While the city has a significant investment in virtual infrastructure, Jordan won't even talk about the technology or its scope, citing security concerns.

With VMware's ESX Server and the other major virtualization platforms, the data that passes between virtual machines is unencrypted. Aravamudan says encryption is being "actively considered" at VMware, but he declined to say when it might be added to the company's products.

Systems like VMware's vShield and other third-party tools can create virtual firewalls that segment VMware, XenServer, Hyper-V and other virtual machines into different security zones, but not all organizations have implemented them. For example, the creation of secure zones hasn't been a big focus at Rent-A-Center. But as the virtual infrastructure scales up, that's becoming a necessity, says Condit.

Some existing firewall tools have visibility into virtual server traffic, but in other cases IT needs to add another set of virtualization-specific tools, and that adds to management complexity.

It's better to have a tool set that spans both the physical and virtual environments, says Neil MacDonald, an analyst at Gartner Inc. Until the traditional security tool vendors catch up, however, IT may need to bring in tools from lesser-known vendors like Altor Networks, Catbird Networks and HyTrust that have been tailored specifically to virtual machines.

More important, the core network architectures need to change to accommodate virtualization, says RSA's Mulé. "Networks that work correctly with physical servers don't necessarily work well with virtual machines. Security would be improved if proper routing and subnets and virtual LANs were implemented," he says. Most business continuity failures in virtualized settings can be attributed to network design flaws, he contends.

Matthew Nowell, senior systems engineer at Six Flags, uses virtual LANs to segregate virtual servers. "Depending on how we set up routing rules, they may or may not be able to talk to each other," he says.

But MacDonald cautions that "VLANs and router-based access controls alone are not sufficient for security separation." The research firm's guidelines call for the deployment of some sort of virtualization-aware firewall.

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The Virtual Enforcer

Third-party vendors such as Trend Micro Inc. are offering add-on software to beef up the security of the hypervisor layer. But some experts worry that as the layer gets more crowded and complex, it becomes a bigger target for security attacks. For more on this topic, see our story "Hypervisor as Virtualization's Enforcer?"

At the Phoenix city government, Jordan insists that systems administrators isolate each virtual server within its own security zone. "I had to fight with server admins who swear up and down that the hypervisor can do that. But I trust firewalls more than I trust hypervisors," she says.

Security From the Start

Securing a virtual infrastructure isn't about buying more tools, says RSA's Baize. "There's a lot available today in terms of controls for virtual infrastructure. What is lacking is the understanding of what the controls are for and when they should be applied," he says.

The best way to create a secure virtual infrastructure is to get security experts involved early. Gartner estimates that as many as 40% of IT shops don't seek IT security's input on a virtual deployment until after the system is already built and online.

The problem becomes more evident as mission-critical applications move into virtual machines. "When you start looking at virtualizing SharePoint or Exchange or ERP, you really are running into sensitive data. That forces the issue," MacDonald says.

By then, organizations are trying to bolt on security that should have been designed in from the beginning. That kind of after-the-fact redesign work can get expensive. "CIOs should make sure they have their top people in the loop when designing this type of architecture," MacDonald says.

It all comes down to policy, contends Condit. "If you don't have a strong security policy in place, a virtual infrastructure is going to show up those weaknesses much more quickly because things happen more rapidly," he says, referring to how quickly virtual servers can be created and then moved around between physical host servers.

CIOs are right to worry. Says Condit, "A certain healthy level of paranoia is always a good thing."

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