This is a nine page overview that does a reasonably good job of laying out many of the architectural/topological options available when thinking about taking the steps toward virtualizing what some consider the "final frontier" in the proving grounds of production-level virtualization -- the (Internet-facing) DMZ.
The whitepaper was timely because I was just finishing up my presentation for Blackhat and was busy creating a similar set of high-level architectural examples to use in my presentation. I decided to reference those in the document because they quite elegantly represent the starting points that many folks would use as a stepping off point in their virtual DMZ adventures.
...and I think it will be an adventure punctuated perhaps by evolutionary steps as documented in the options presented in the whitepaper.
As I read through the document, I had to remind myself of the fact that this was intended to be a high-level document and not designed to cover the hairy edges of network and security design.
The whitepaper highlighted some of the reasonable trade-off's in complexity, resiliency, management, functionality, operational expertise, and cost but given where my head and focus are today, I have to admit that it still gnawed at me from a security perspective which is still too weak for my liking.
Alessandro got dinged in a comment on his blog for a statement in which he suggested that partially-collapsed as well as fully-collapsed DMZ's with virtual separation of trust zones "...should be avoided at all costs because they imply the inviolability of the hypervisor (at any level: from the virtual networking to the kernel) something that nor VMware neither any other virtualization vendor can grant."
This appears contradictory to his initial assessment of DMZ virtualization wherein he stated that "...there [is] nothing bad in virtualizing the DMZ as long as we are fully aware of the risks." In a way, I think I understand exactly where Alessandro is coming from, even if I don't completely agree with him (or at least I partially do...)
This really paints an altogether unfortunate and yet accurate picture of the circular arguments folks engage in when they combine the following topics in a single argument:
- Securing virtualization
- Virtualizing security
- Security via virtualization
In the same way that we trust our operating system vendors who provide us with the operational underpinnings of our datacenters with the hope that they will approach a reasonable level of "security" in their products, we are basically at the same point with our virtualization (OS) platform providers.
Hope is not a strategy, but it seems we've at least accepted it for the time being... ;(
Sure there are new attack vectors and operational risks, but the slippery slope of not being able to really quantify whether you are more or less at risk based solely on the one-dimensional data point of the infallibility of the hypervisor and then write the whole concept off seems a little odd to me.
If you're truly assessing risk in the potential virtualization of your DMZ, you'll take the operational/architectural guidelines as well as the subjective business impacts into consideration. Simply stating that one should or should not virtualize a DMZ without a holistic approach is myopic.
To circle back on the topic, the choice of whether to -- and how to -- virtualize your DMZ is really starting to gain traction. I think the whitepaper took a decent first-pass stab at exploring how one might approach it, but the devil's in the details -- or at least the devil's 4 horsemen are ;)