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The Unbearable Lightness of Being…Virtualized

My apologies to Pete Lindstrom for not responding to his comment regarding my "virtualization & defibrilation" post sooner and hat-tip for Rothman for the reminder.

Pete was commenting on a snippet from my larger post dealing with the following assertion:

The Hoff-man pontificates yet again:

Firewalls, IDS/IPSs, UTM, NAC, DLP — all of them have limited
visibility in this rapidly "re-perimeterized" universe in which our
technology operates, and in most cases we’re busy looking at
uninteresting and practically non-actionable things anyway.  As one of
my favorite mentors used to say, "we’re data rich, but information

a general sense, I agree with this statement, but in a specific sense,
it isn’t clear to me just how significant this need is. After all, we
are talking today about 15-20 VMs per physical host max and I defy
anyone to suggest that we have these security solutions for every 15-20
physical nodes on our network today – far from it.

Let’s shed a little light on this with some context regarding *where* in the network we are virtualizing as I don’t think I was quite clear enough.

Most companies have begun to virtualize their servers driven by the economic benefits of consolidation and have done so in the internal zones of the networks.  Most of these networks are still mostly flat from a layer 3 perspective, with VLANs providing isolation for mostly performance/QoS reasons.

In discussions with many companies ranging from the SME to the Fortune 10, all except a minority are virtualizing hosts and systems placed within traditional DMZ’s facing external networks.

From that perspective, I agree with Pete.  Most companies are still grappling with segmenting their internal networks based on asset criticality, role, function or for performance/security reasons, so it stands to reason that internally we don’t, in general, see "…security solutions for every 15-20
physical nodes on our network today,"
but we certainly do in externally-facing DMZ’s.

However, that’s changing — and will continue to — as we see more and more basic security functionality extend into switching fabrics and companies begin to virtualize security policies internally.  The next generation of NAC/NAP is good example.  Internal segmentation will drive the need for logically applying combinations of security functions virtualized across the entire network space.

Furthermore, there are companies who are pushing well past the 15-20 VM’s per host, and that measure is really not that important.  What is important is the number of VM’s on hosts per cluster.  More on that later.

That said, it isn’t necessarily a great argument for me simply to
suggest that since we don’t do it today in the physical world that we
don’t have to do it in the virtual world. The real question in my mind
is whether folks are crossing traditional network zones on the same physical box.
That is, do trust levels differ among the VMs on the host? If they
don’t, then not having these solutions on the boxes is not that big a
deal – certainly useful for folks who are putting highly-sensitive
resources in a virtual infrastructure, but not a lights-out problem.

The reality is that as virtualization platforms become more ubiquitous, internal segmentation and more strict definition of host grouping in both virtualized and non-virtualized server clusters will become an absolute requirement because it’s the only way security policies will be able to be applied given today’s technology. 

This will ultimately then drive to the externally-facing DMZ’s over time.  It can’t not.  However, today, the imprecise measurement of quantifiable risk (or lack thereof) combined with exceptionally large investment in "perimeter" security technologies, keeps most folks at an arm’s length from virtualizing their DMZ’s from a server perspective.  Lest we forget our auditor friends and things like PCI/DSS which complicate the issue.

Other’s might suggest that with appropriately architected multi-tier environments combined with load balanced/clustered server pools and virtualized security contexts, the only difference between what they have today and what we’re talking about here is simply the hypervisor.  With blade servers starting to proliferate in the DMZ, I’d agree.

Until we have security policies that are, in essence, dynamically instantiated as they are described by the virtual machines and the zones into which they are plumbed, many feel they are still constrained by trying to apply static ACL-like policies to incredibly dynamic compute models.

So we’re left with constructing little micro-perimeter DMZ’s throughout the network. 

If the VMs do cross zones, then it is much more important to have
virtual security solutions. In fact, we don’t recommend using virtual
security appliances as zone separators simply because the hypervisor’s
additional attack surface introduces unknown levels of risk in an
environment. (Similarly, in the physical world we don’t recommend
switch-based security solutions as zone separators either).

What my research is finding in discussion with some very aggressive
companies who are embracing virtualization is that starting internally
— and for some of the reasons like performance which Pete mentions —
companies are beginning to setup clusters of VM’s that do indeed "cross
the streams." 😉

I am told by our virtualization technical expert that there may be
performance benefits to commingling resources in this way, so at some
point it will be great to have these security solutions available. I
suppose we should keep in mind that any existing network security
solution that isn’t using proprietary OS and/or hardware can migrate
fairly easily into a virtual security appliance.

There are most certainly performance "benefits" — I call them band-aids — to co-mingling resources in a single virtual host.  Given the limitations of today’s virtual networking and the ever-familiar I/O bounding we experience with higher-than-acceptable latency in mainstream Ethernet-based connectivity, sometimes this is the only answer.  This is pushing folks to consider I/O virtualization technologies and connectivity other than Ethernet such as InfiniBand.

The real issue here that I have with the old "just run your tired old security solutions as a virtual appliance within a virtual host" is the exact reason that I alluded to in the quote Pete singled in on.  We lose visibility, coherence and context using this model.  This is the exact reason for something like VMsafe, but will come with a trade-off I’ve already highlighted.

The thinner the hypervisor, the more internals will need to be exposed via API to external functions.  While the VMM gets more compact, the attack surface expands via the API.

Keep in mind that we have essentially ignored the whole
de-perimeterization, network without borders, Jericho Forum
predisposition to minimize these functions anyway. That is, we can
configure the functional VMs themselves with better security
capabilities as well.

Yes, we have ignored it…and to our peril.  Virtualization is here. It will soon be in your DMZ if it isn’t already.  If you’re not seriously reconsidering the implications that virtualization (of servers, storage, networking, security, applications, data, etc.) has on your datacenter — both in your externally-facing segments and your internal networks —  *now* you are going to be in a world of hurt within 18 months.


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  1. March 12th, 2008 at 13:19 | #1

    This continuum between getting the new virtual infrastructure to mimic the replaced physical one (security wins out over utilization/flexibility economics) may be the only way that netsec can longlife their deep packet plus architectures. If enterprises shift to rack and stack meshes I think it will be the end of core layer 4 pattern/anomaly match as a method of sane security policy enforcement.
    I think there are two key drivers: 1) mutation and evasion on the outside and 2) movement and change/mutation [snapshot, clone, revert, vmotion] on the inside. How does an IPS protect zones if it cannot see inter-VM traffic? As environments get fuzzy and move, etc then the value/power of "known exploit signatures" and other static mechanisms erode faster and can even cause onerous side effects if deployed in block mode.
    Even with agents/sensors deployed by hypervisor they represent choke points that could compromise the business case for virtualization and force enterprises into a "Back to the Future" posture.
    Blue Lane

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