  Facing the dynamic complex cyber environments, internal and external cyber
threat intelligence, and the increasing risk of cyber-attack, knowledge graphs
show great application potential in the cyber security area because of their
capabilities in knowledge aggregation, representation, management, and
reasoning. However, while most research has focused on how to develop a
complete knowledge graph, it remains unclear how to apply the knowledge graph
to solve industrial real challenges in cyber-attack and defense scenarios. In
this review, we provide a brief overview of the basic concepts, schema, and
construction approaches for the cyber security knowledge graph. To facilitate
future research on cyber security knowledge graphs, we also present a curated
collection of datasets and open-source libraries on the knowledge construction
and information extraction task. In the major part of this article, we conduct
a comparative review of the different works that elaborate on the recent
progress in the application scenarios of the cyber security knowledge graph.
Furthermore, a novel comprehensive classification framework is created to
describe the connected works from nine primary categories and eighteen
subcategories. Finally, we have a thorough outlook on several promising
research directions based on the discussion of existing research flaws.
