What is the likelihood of a threat occurring and leading to the final consequence without any cybersecurity countermeasures called?

The term that describes the likelihood of a threat occurring and resulting in the final consequence without any cybersecurity countermeasures is indeed Unmitigated Threat Likelihood (UTL). UTL specifically refers to the assessment of how probable a specific threat is, based on its potential to exploit vulnerabilities in a system when there are no defenses in place.

When evaluating risks, understanding UTL is critical because it establishes a baseline for the potential impact of a threat in a worst-case scenario, where no protective measures are implemented. This concept plays an essential role in risk assessments as it helps organizations prioritize their cybersecurity investments and enhances their understanding of the inherent risks associated with their industrial automation and control systems (IACS).

In contrast, terms like Risk Severity refer to the impact or consequences of a risk event rather than the likelihood of its occurrence. Mitigated Threat Likelihood (MTL) would denote the likelihood of a threat occurring after countermeasures have been applied, thus differentiating it from UTL. The Contingent Risk Factor does not specifically capture the probability of a threat's occurrence without mitigation, making it less relevant in this context.