The document discusses security challenges posed by virtualization and cloud computing. It outlines three stages in the evolution of data centers from consolidation to private and public clouds. This evolution introduces new security challenges including inter-VM attacks, vulnerabilities in dormant or cloned VMs, and difficulties maintaining compliance across complex cloud environments. The document proposes that security solutions need to improve performance in virtual environments, provide visibility across platforms, and integrate management to address threats consistently across physical, virtual and cloud systems.