Details
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.
NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
Solution
From the vSphere Web Client go to Networking >> Select a distributed switch >> Select a port group >> Configure >> Settings >> Policies >> Edit >> Security. Set ‘Forged Transmits’ to reject. Click ‘OK’.
or
From a PowerCLI command prompt while connected to the vCenter server run the following commands:
Get-VDSwitch | Get-VDSecurityPolicy | Set-VDSecurityPolicy -ForgedTransmits $false
Get-VDPortgroup | ?{$_.IsUplink -eq $false} | Get-VDSecurityPolicy | Set-VDSecurityPolicy -ForgedTransmits $false
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: Configuration Management.This control applies to the following type of system VMware.
References
- 800-53|CM-6b.
- CAT|II
- CCI|CCI-000366
- Rule-ID|SV-216835r612237_rule
- STIG-ID|VCWN-65-000013
- STIG-Legacy|SV-104567
- STIG-Legacy|V-94737
- Vuln-ID|V-216835