A standardized vulnerability score is identified for a particular vulnerability in a plurality of known vulnerabilities, the standardized vulnerability score indicating a relative level of risk associated with the particular vulnerability relative other vulnerabilities. A vulnerability detection score is determined that indicates an estimated probability that a particular asset possess the particular vulnerability and a vulnerability composite score is determined for the particular asset to the particular vulnerability, the vulnerability composite score derived from the standardized vulnerability score and the vulnerability detection score. A countermeasure component score is identified that indicates an estimated probability that a countermeasure will mitigate risk associated with the particular vulnerability on the particular asset. A risk metric for the particular asset and the particular vulnerability is determined from the vulnerability composite score and the countermeasure component score. In some instances, aggregate risk scores can be calculated from a plurality of calculated risk metrics.