Which of the following risk factors is measured in Numbers (#)?

The measurement of risk factors in numerical terms is crucial for quantifying and understanding risk dynamics. Threat Event Frequency (TEF) specifically refers to the estimated frequency at which threat events occur within a defined time period. This quantification allows organizations to assess how often they might face specific threats and is instrumental in risk calculation.

In risk assessment frameworks, the ability to express the frequency of threat events in numerical form enables organizations to prioritize their response strategies, allocate resources effectively, and implement appropriate mitigation measures. By having a clear numerical value for TEF, organizations can make more informed decisions about their security postures and risk management practices.

Other options, while relevant to risk assessment, do not specifically measure frequency in direct numerical terms. For instance, Threat Contact Frequency correlates more with the interactions that can lead to a threat rather than providing a direct numerical representation. Threat Evaluation Factor typically involves qualitative assessments evaluating the significance or impact of a threat. Meanwhile, the Vulnerability Index often expresses the susceptibility of systems rather than focusing on frequency. Thus, the unique characteristic of TEF being explicitly measured in numerical terms makes it the correct answer in this context.