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Can a DMZ Virtual Machine and an Internal Virtual Machine share the same host.

Posted on 2013-11-24
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Last Modified: 2013-11-25
Using Microsoft Server 2012 R2 hyper-v Virtual machines:

Assume a host server running Server2012R2, called HostA.

HostA has two NICs, and has two separate virtual switches, one on each NIC:
Switch1 on NIC1
Switch2 on NIC2

NIC1 is physically wired to a LAN port on the network firewall.
NIC2 is physically wired to a DMZ port on the network firewall.

Next, build 2 Virtual Machines: VM1 and VM2

VM1 has an IP address compatible with the internal LAN and is put on Switch1.
VM2 has a DMZ IP address and is put on Switch2.

Are these two virtual machines, VM1 and VM2, as completely separated from each other as if they were two physical machines with 2 physically distinct network cards?

In other words, and a DMZ VM and an internal VM share the same host if everything is properly configured, or is there some kind of risk I am not thinking of?

Thanks.
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Question by:gateguard
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Qlemo earned 250 total points
ID: 39673001
The VMs should be isolated from each other in that configuration. There might be some exploits, but that is very unlikely, as the effort would be enormous to break the VM barrier. But since the Hyper-V VMs share some code, there is always a risk by getting one VM compromised. However, if you do not need to apply very high security measures, the config would get my ok.
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by:alexziv
ID: 39673004
they will be in a lan witct is made by your host machine, and they will see each other , try nmap on all, after you configure them, host and vm1/vm2
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by:Qlemo
ID: 39673012
alexziv, that is nonsense. The virtual switches isolate VMs from each other, that is their purpose.
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by:alexziv
ID: 39673018
sorry, reading fast
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by:Ram Balachandran
Ram Balachandran earned 250 total points
ID: 39673021
The only way for VMs to talk to each other is through the network stack.  Therefore, if someone were to compromize your DMZ VM, they would have to use its internet connection to compromize your internal network.  In order to prevent someone from accessing your host from the DMZ, you'll want to configure Hyper-V so the virtual network is not available to the host and only to the VMs.  Also, you'll want to ensure that your management network is secure on the internal LAN.I would also suggest that if you are trying to implement a DMZ, take a look at Microsoft Forefront Threat Management Gateway / ISA.  This can be used to create an application publishing DMZ which sits behind your boundary firewall.

It is worth referring this

http://social.technet.microsoft.com/Forums/en-US/8032789f-c431-4af7-b56b-adf57ec241bc/hyperv-network-security

http://technet.microsoft.com/en-us/library/gg610642.aspx


link
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Author Closing Comment

by:gateguard
ID: 39673046
Thanks!
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Expert Comment

by:Giovanni Heward
ID: 39675020
There are proved VM escape exploits.  It would be unwise to assume there are no undisclosed exploits in existence nor existing vulnerabilities which could be discovered and exploited in the future.  While existing (disclosed) exploits may be for alternate products, I would take the overall track record of Microsoft into consideration, as it pertains to software vulnerabilities.

One proven method of mitigation would be to properly deploy EMET.  Its my recommendation that this product be deployed on all Windows-based operating systems, as part of your defense-in-depth strategy, after throughout application compatibility testing.

EMET uses security mitigation technologies such as Data Execution Prevention (DEP), Mandatory Address Space Layout Randomization (ASLR), Structured Exception Handler Overwrite Protection (SEHOP), Export Address Table Access Filtering (EAF), Anti-ROP, and SSL/TLS Certificate Trust Pinning, to help protect computer systems from new or undiscovered threats. EMET can also protect legacy applications or third party line of business applications where you do not have access to the source code.

That said-- considering the complexity involved-- I would agree that the most likely attack vector would be through the network stack.

Best defense-in-depth security practices however would call for physical isolation.  At the end of the day its all about risk.  Consider the value of the data you are protecting vs. the cost to protect that data.  Qualitative/Quantitative risk assessment is a good starting point.
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