Xen is a mature enterprise-grade virtual machine with many advanced security features which are unique to Xen. For this reason it's the hypervisor of choice for the NSA, the DoD, and the new QubesOS Secure Desktop project. While much of the security of Xen is inherent in its design, many of the advanced security features, such as stub domains, driver domains, XSM, and so on are not enabled by default. This session will describe all of the advanced security features of Xen, and the best way to configure them for the Cloud environment. When the audience leaves, they should have a general framework to evaluate the security of their system, know the key security features of Xen, and have a basic framework of knowledge to help them make sense of the documentation. This talk will *not* go into mind-numbing detail about specific commands to type or configuration options.