Security is a growing concern as it remains the last barrier to widespread adoption of cloud environments. However, is today's cloud security Lucy in the Sky with Diamonds? Expected to be strong, flexible, efficient, and simple? But surprisingly, being neither? A new approach, making clouds self-defending, has been heralded as a possible element of answer to the cloud protection challenge. This paper presents an overview of today's state and advances in the field of cloud infrastructure self-defense. Four key self-protection principles are identified for IaaS self-protection to be effective. For each layer, mechanisms actually deployed to deliver security are analyzed to see how well they fulfill those principles. The main remaining research challenges are also discussed to yield truly mature self-defending clouds