The rule 'Untrusted DLL Loaded by Azure AD Sync Service' is designed to detect the loading of a dynamically linked library (DLL) file without a valid code signature by the Azure AD Sync process. This operation can signify malicious activity aimed at intercepting or stealing sensitive credentials handled by the Azure AD synchronization server. The detection mechanism leverages Elastic's EQL (Event Query Language) and targets Windows environments, specifically monitoring processes like 'AzureADConnectAuthenticationAgentService.exe'. The query inspects events related to the loading of libraries or processes that deviate from trusted sources or pre-defined safe paths. This rule emphasizes on credential access tactics and assigns a risk score of 73, classifying the threat severity as high. The accompanying investigation guide details triage procedures, potential false positives, and remediation steps to address identified risks, elevating the importance of prompt responses to alerts while ensuring system integrity.