Which term refers to the competency level of a threat actor?

The term that best refers to the competency level of a threat actor is "Capability." This term encompasses not just skill or expertise but also the resources available to a threat actor, including tools, knowledge, and operational tactics that enable them to carry out attacks effectively. It provides a broader understanding of what a threat actor can do and their potential impact, which is critical for assessing the risk posed by various actors in cybersecurity. Capability considers the full spectrum of a threat actor's potential actions, which includes how they may leverage their skills and expertise in a real-world context to exploit vulnerabilities.

The options of skill level and proficiency typically refer to specific areas of ability rather than a comprehensive understanding of what a threat actor can achieve overall. Expertise, while it denotes a high level of skill, still does not capture the entirety of a threat actor's potential when considering various factors that influence their actions. Therefore, "Capability" is the term that most accurately encapsulates the various dimensions of a threat actor's competency.