The rule is designed to detect potential Dynamic Link Library (DLL) sideloading of the 'vivaldi_elf.dll' on Windows systems. DLL sideloading is a technique where a malicious DLL is loaded by a legitimate application, effectively allowing an attacker to execute harmful code within the context of a trusted application. This detection mechanism works by monitoring the 'ImageLoaded' event to see if the loaded image ends with 'vivaldi_elf.dll'. Further refinements incorporate a filter that checks the legitimacy of the source application, specifically targeting the Vivaldi browser's executable located in its Application folder. If the loaded DLL is found to have come from an unexpected path while still being associated with the Vivaldi application, it triggers a potential sideloading alert. This rule uses a combination of selection and filtering conditions to effectively reduce false positives, although a few unknowns can arise based on the environment in which the monitoring takes place.