vNetwork : reject-forged-transmit-dvportgroup

Information

Ensure that the Forged Transmits policy is set to reject.
If the virtual machine operating system changes the MAC address, the operating system can send frames with an impersonated source MAC address at any time. This allows an operating system to stage malicious attacks on the devices in a network by impersonating a network adaptor authorized by the receiving network.

When the Forged transmits option is set to Accept, ESXi does not compare source and effective MAC addresses.

To protect against MAC impersonation, you can set the Forged transmits option to Reject. If you do, the host compares the source MAC address being transmitted by the guest operating system with the effective MAC address for its virtual machine adapter to see if they match. If the addresses do not match, the ESXi host drops the packet.

http://pubs.vmware.com/vsphere-60/topic/com.vmware.vsphere.networking.doc/GUID-891147DD-3E2E-45A1-9B50-7717C3443DD7.html

http://pubs.vmware.com/vsphere-60/topic/com.vmware.vsphere.security.doc/GUID-C590B7D3-4E28-4F2B-8A59-4CDB9C6F2DAA.html

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

From vSphere Web Client, for each portgroup within each distributed switch go to "Manage" -> "Settings" -> "Policies" and click "Edit". Go to "Security" and set the "Forged transmits" policy to "Reject".

See Also

https://www.vmware.com/content/dam/digitalmarketing/vmware/en/files/xls/vSphere_6_0_Hardening_Guide_GA_15_Jun_2015.xls