Exploring Layer 2 Network Security in Virtualized Environments presented at Defcon 2015

by Ronny L. Bull, Jeanna N. Matthews,

Summary : Cloud service providers offer their customers the ability to deploy virtual machines in a multi-tenant environment. These virtual machines are typically connected to the physical network via a virtualized network configuration. This could be as simple as a bridged interface to each virtual machine or as complicated as a virtual switch providing more robust networking features such as VLANs, QoS, and monitoring. In this paper, we explore whether Layer 2 network attacks that work on physical switches apply to their virtualized counterparts by performing a systematic study across four major hypervisor environments - Open vSwitch, Citrix XenServer, Microsoft Hyper-V Server and VMware vSphere - in seven different virtual networking configurations. First, we use a malicious virtual machine to run a MAC flooding attack and evaluate the impact on co-resident VMs. We find that network performance is degraded on all platforms and that it is possible to eavesdrop on other client traffic passing over the same virtual network for Open vSwitch and Citrix XenServer. Second, we use a malicious virtual machine to run a rogue DHCP server and then run multiple DHCP attack scenarios. On all four platforms, co-resident VMs can be manipulated by providing them with incorrect or malicious network information.