Abstract: Provided is an operation method of an attack risk assessment system, which includes: extracting, when an advanced persistent threat attack is detected, an attack component for the advanced persistent threat attack based on risk-aware problem domain ontology for assessing a security risk for an attack; identifying a risk component based on the attack component; deriving a security requirement by a goal based access scheme set for the risk component; and assessing the security risk based on an evidence set through a relationship between a domain asset identified as the risk component and the security requirement.