6.7

Table Of Contents
The security policy determines how strongly you enforce protection against impersonation and
interception attacks on VMs. To correctly use the settings in the security profile, see the Security Policy
section in the vSphere Networking publication. This section explains:
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How VM network adapters control transmissions.
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How attacks are staged at this level
Securing vSphere Standard Switches
You can secure standard switch traffic against Layer 2 attacks by restricting some of the MAC address
modes of the VM network adapters.
Each VM network adapter has an initial MAC address and an effective MAC address.
Initial MAC address The initial MAC address is assigned when the adapter is created. Although
the initial MAC address can be reconfigured from outside the guest
operating system, it cannot be changed by the guest operating system.
Effective MAC address Each adapter has an effective MAC address that filters out incoming
network traffic with a destination MAC address that is different from the
effective MAC address. The guest operating system is responsible for
setting the effective MAC address and typically matches the effective MAC
address to the initial MAC address.
Upon creating a VM network adapter, the effective MAC address and initial MAC address are the same.
The guest operating system can alter the effective MAC address to another value at any time. If an
operating system changes the effective MAC address, its network adapter receives network traffic that is
destined for the new MAC address.
When sending packets through a network adapter, the guest operating system typically places its own
adapter effective MAC address in the source MAC address field of the Ethernet frames. It places the MAC
address for the receiving network adapter in the destination MAC address field. The receiving adapter
accepts packets only if the destination MAC address in the packet matches its own effective MAC
address.
An operating system can send frames with an impersonated source MAC address. An operating system
can therefore impersonate a network adapter that the receiving network authorizes, and stage malicious
attacks on the devices in a network.
Protect virtual traffic against impersonation and interception Layer 2 attacks by configuring a security
policy on port groups or ports.
The security policy on distributed port groups and ports includes the following options:
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MAC address changes (see MAC Address Changes)
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Promiscuous mode (see Promiscuous Mode Operation)
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Forged transmits (see Forged Transmits)
You can view and change the default settings by selecting the virtual switch associated with the host from
the vSphere Web Client. See the vSphere Networking documentation.
vSphere Security
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