Penetration test results are the most helpful resource to a risk practitioner when updating the likelihood rating in the risk register. Penetration testing is a method of simulating real-world attacks on an IT system or network to identify and exploit vulnerabilities and measure the potential impact. Penetration test results provide empirical evidence of the existence and severity of vulnerabilities, as well as the ease and probability of exploitation. These results can help the risk practitioner to update the likelihood rating of the risks associated with the vulnerabilities, and to prioritize the risk response actions. Risk control assessment, audit reports with risk ratings, and business impact analysis (BIA) are also useful resources for risk management, but they are not as directly related to the likelihood rating as penetration test results. References = Risk and Information Systems Control Study Manual, Chapter 2, Section 2.3.3, page 2-28.