Final answer:
The likelihood of occurrence is based on adversary intent, their capability, how much they're targeting the entity, and the potential impact of the threat.
Step-by-step explanation:
The likelihood of occurrence in the context of security risks or threats is primarily based on several factors: adversary intent, adversary capability, and adversary targeting. Additionally, the potential impact of a threat can influence how likely it is considered to occur. If an adversary has a strong intent to disrupt, damage, or gain from targeting an entity, and if they have the capabilities to do so, the likelihood of occurrence is higher. Adversary targeting refers to how much an entity is being specifically targeted by an adversary, which also contributes to the likelihood. Lastly, the impact concerns what effect the threat would have if it were to occur; higher impact events might be more or less likely depending on whether those increase an adversary’s motivation to undertake the effort to realize the threat.