Whether or not security alone will be a reason to virtualize applications, the growing trend of virtualization require us to understand to new capabilities for hypervisor based security monitoring. In this presentation we will review the basic monitoring primitives an hypervisor can provide as building blocks to security agents. Following with a review of the use cases we identified as the most likely to be developed on this new technology. The presentation will review the generic potential of hypervisor based security in a vendor neutral way, while live demos will be based on VMware VMsafe APIs.