  Cybersecurity Dynamics is new concept that aims to achieve the modeling,
analysis, quantification, and management of cybersecurity from a holistic
perspective, rather than from a building-blocks perspective. It is centered at
modeling and analyzing the attack-defense interactions in cyberspace, which
cause a ``natural'' phenomenon -- the evolution of the global cybersecurity
state. In this Chapter, we systematically introduce and review the
Cybersecurity Dynamics foundation for the Science of Cybersecurity. We review
the core concepts, technical approaches, research axes, and results that have
been obtained in this endeavor. We outline a research roadmap towards the
ultimate research goal, including a systematic set of technical barriers.
