Network security in the vSphere environment shares many characteristics of securing a physical network environment, but also includes some characteristics that apply only with virtual machines.


Add firewall protection to your virtual network by installing and configuring host-based firewalls on some or all of its virtual machines.

For efficiency, you can set up private virtual machine Ethernet networks or virtual networks. With virtual networks, you install a host-based firewall on a virtual machine at the head of the virtual network. This firewall serves as a protective buffer between the physical network adapter and the remaining virtual machines in the virtual network.

Because host-based firewalls can slow performance, balance your security needs against performance goals before you install host-based firewalls on virtual machines elsewhere in the virtual network.

See Securing the Network with Firewalls.


Keep different virtual machine zones within a host on different network segments. If you isolate each virtual machine zone on its own network segment, you minimize the risk of data leakage from one virtual machine zone to the next. Segmentation prevents various threats, including Address Resolution Protocol (ARP) spoofing, in which an attacker manipulates the ARP table to remap MAC and IP addresses, thereby gaining access to network traffic to and from a host. Attackers use ARP spoofing to generate man in the middle (MITM) attacks, perform denial of service (DoS) attacks, hijack the target system, and otherwise disrupt the virtual network.

Planning segmentation carefully lowers the chances of packet transmissions between virtual machine zones, which prevents sniffing attacks that require sending network traffic to the victim. Also, an attacker cannot use an insecure service in one virtual machine zone to access other virtual machine zones in the host. You can implement segmentation by using either of two approaches. Each approach has different benefits.

  • Use separate physical network adapters for virtual machine zones to ensure that the zones are isolated. Maintaining separate physical network adapters for virtual machine zones is probably the most secure method and is less prone to misconfiguration after the initial segment creation.

  • Set up virtual local area networks (VLANs) to help safeguard your network. Because VLANs provide almost all of the security benefits inherent in implementing physically separate networks without the hardware overhead, they offer a viable solution that can save you the cost of deploying and maintaining additional devices, cabling, and so forth. See Securing Virtual Machines with VLANs.

Preventing Unauthorized Access

If your virtual machine network is connected to a physical network, it can be subject to breaches just like a network that consists of physical machines. Even if the virtual machine network is isolated from any physical network, virtual machines in the network can be subject to attacks from other virtual machines in the network. The requirements for securing virtual machines are often the same as those for securing physical machines.

Virtual machines are isolated from each other. One virtual machine cannot read or write another virtual machine’s memory, access its data, use its applications, and so forth. However, within the network, any virtual machine or group of virtual machines can still be the target of unauthorized access from other virtual machines and might require further protection by external means.