What best defines residual risk?

Residual risk is best defined as the amount of risk that remains after security controls and mitigation measures have been implemented. When organizations assess risks, they typically identify various threats, vulnerabilities, and the potential impact of these risks. Once they apply countermeasures, controls, or safeguards to reduce these risks, the level of risk that still exists is termed residual risk.

Implementing controls aims to reduce overall risk, but it is essential to understand that it may not eliminate all risk entirely. Factors like ongoing vulnerabilities, human error, and evolving threats mean that some level of risk will always persist. Thus, assessing and understanding the residual risk allows organizations to make informed decisions about further investments in security and risk management efforts.

In contrast, the other options relate to different risk concepts. The risk before countermeasures pertains to the initial risk level before any actions are taken. The total risk after assessments does not account for the mitigation efforts and is more reflective of the calculated risks before controls. The inherent risk after controls does not accurately encapsulate the situation, as inherent risk refers to the risk present in the absence of any controls, whereas residual risk specifically indicates what remains after those controls have been implemented.