  Social engineering has posed a serious threat to cyberspace security. To
protect against social engineering attacks, a fundamental work is to know what
constitutes social engineering. This paper first develops a domain ontology of
social engineering in cybersecurity and conducts ontology evaluation by its
knowledge graph application. The domain ontology defines 11 concepts of core
entities that significantly constitute or affect social engineering domain,
together with 22 kinds of relations describing how these entities related to
each other. It provides a formal and explicit knowledge schema to understand,
analyze, reuse and share domain knowledge of social engineering. Furthermore,
this paper builds a knowledge graph based on 15 social engineering attack
incidents and scenarios. 7 knowledge graph application examples (in 6 analysis
patterns) demonstrate that the ontology together with knowledge graph is useful
to 1) understand and analyze social engineering attack scenario and incident,
2) find the top ranked social engineering threat elements (e.g. the most
exploited human vulnerabilities and most used attack mediums), 3) find
potential social engineering threats to victims, 4) find potential targets for
social engineering attackers, 5) find potential attack paths from specific
attacker to specific target, and 6) analyze the same origin attacks.
