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Re: ESX Vmware Physically connected to different segments
From: "David M. Zendzian" <dmz () dmzs com>
Date: Mon, 28 Jan 2008 15:32:41 -0500

Yes it does make you think twice when considering such a design, however I am not familiar with exploits at a guest domain that would effect the host specifically. While yes in 'theory' there could be some kernel hook that could allow a guest to access the host server, and I hate to be in a situation when one arrives; however, the same argument also applies to shared virtual web hosts, but only the largest companies have dedicated hosts for every domain, there will always be sharing happening which is why virtual environments are growing in popularity.

Would it not be better to examine the hooks in systems that allow communication / buffers / etc in virtual environments and help ensure that they are done correctly? I know this is not really possible with VMWare, but with Xen & other systems where the code is available the issues can at least be investigated.

Now if someone has code (links/docs/etc) available the detail attacks on guests effecting hosts (DOS not included, exploits taking control of services of a host from a guest, or accessing network or resources not setup for that guest), then please post them to the list so we can discuss the issues and how to address them.

These same questions might also be applied to VLANs or other types of virtualization techniques that allow for greater use of the devices we have available. While there are fun ways to attack network vlans to access security domains outside of configured settings, it is the disclosure of these techniques that allowed for providers to secure the tools to a point where I know of no business I've ever worked with have dedicated network devices for every network. While I have seen different equipment on "DMZ vs Internal" networks, most still use VLAN security to segment those as well (it's a $ thing & usually a complexity thing, more parts means more people to manage, understand, change w/ out breaking, etc).

I believe there are ways of deploying virtual technology that may not prevent the theoretical attack, at least provide protection against the common attacks and provide for a viable solution for the small business' I work with.

The only way to be secure is to unplug, the rest of us have to work for a living :)


Kurt Buff wrote:
Even if everything is configured properly, mixing security domains in
a virtual hosting is a capital mistake.

That's because the underlying host is also vulnerable, and attacks
against a guest OS in an untrusted domain can be leveraged against the
host, and from there *all* guest OSes are toast, or near to it.

Don't do it, ever.


On Jan 28, 2008 5:08 AM, Loupe, Jeffrey J <JLoupe () whitneybank com> wrote:
If everything is setup properly this configuration should be secure. The
problem comes with misconfiguration. It's exceedingly easy for a
careless admin to connect a vNic to the wrong vSwitch and allow traffic
meant for the DMZ onto the trusted network. In general we disallow this
practice unless only one or two trusted admins have control of the box.
Even then, we audit the configuration frequently.



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