How is risk defined in RMF, and how does it influence the Authorization to Operate (ATO) decision?

• A. The potential for adverse impact due to threats exploiting vulnerabilities; residual risk after controls informs the AO’s decision.
• B. The likelihood of a successful attack is the sole determinant of ATO.
• C. Risk is static and does not change with controls.
• D. The potential for adverse impact due to threats exploiting vulnerabilities; compliance with controls directly determines the ATO.

Answer: (A)

In RMF, risk means the potential for an adverse impact to operations, assets, or individuals if threats exploit vulnerabilities. Implementing security controls reduces this risk, but some risk often remains after controls are in place—that's the residual risk. The Authorization Official bases the ATO decision on this residual risk, considering whether it is acceptable for the system's mission, environment, and the organization’s ability to monitor and manage risk over time. If the residual risk falls within tolerance, an ATO is granted; if it does not, additional mitigations are needed or authorization may be withheld.

Compliance with controls is necessary, but not alone sufficient to decide the ATO—the key factor is whether the remaining risk after controls is acceptable.