8.4.26 Ensure all but VGA mode on virtual machines is disabled

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Information

Enable VGA Only mode for the Virtual Machine video card.

Note:this setting should only be applied to those virtual machines for which a video card is not needed such as Windows Server Core and UNIX / Linux servers.

Rationale:

Many Server-class virtual machines need only a standard VGA console (typically a Unix/Linux server or Windows Server Core system). Enabling this setting removes additional unnecessary graphics functionality beyond disabling 3D. This reduces the potential attack surface available for malicious attacks.

Impact:

Configuring this setting to True will not allow any advanced graphics functions to work. Only character-cell console mode will be available. Use of this setting renders mks.enable3d moot. The mks.enable3d has no effect.

Note: this setting should only be applied to those virtual machines for which a video card is not needed such as Windows Server Core and UNIX / Linux servers.

Solution

Check that the virtual machine advanced setting of 'svga.vgaonly' is set to TRUE.
To modify the advanced settings of a virtual machine using the vSphere Client:

Ensure that the virtual machine has been shutdown and is powered off.

Right-click on the virtual machine.

Click Edit Settings... to open the Virtual Machine Properties window.

Click the VM Options tab.

From the list on the left, click Advanced.

On the Configuration Parameters frame on the right, click Edit Configuration ...

Click Add Parameter.

On the new row, click under the Key column and specify the configuration option name.

On the new row, click under the Value column and specify the configuration value.

Start the virtual machine for the settings take effect.

Additionally, the following PowerCLI command may be used:

# Add the setting to all VMs
Get-VM | New-AdvancedSetting -Name 'svga.vgaOnly' -value $true

Default Value:

The prescribed state is not the default state.

See Also

https://workbench.cisecurity.org/files/3511