Indexed custom event properties in IBM Security QRadar SIEM are designed to optimize the search process by narrowing down the overall data set. When a property is indexed, QRadar can more efficiently locate events or flows that match the search criteria, thereby reducing the overall volume of data that needs to be searched and enhancing performance. This is reflected in statement B, where indexed filters eliminate portions of the data set that are not relevant to the search query, effectively reducing the number of event or flow logs that must be examined .

Moreover, the use of indexed event and flow properties for optimizing searches is a recommended practice in QRadar. By selectively indexing properties that are frequently used in searches, analysts can significantly improve the speed and efficiency of their queries. This approach is beneficial in environments where quick access to specific event or flow data is crucial for timely threat detection and response. Therefore, statement E highlights the importance of utilizing indexed properties to streamline the search process and facilitate more effective security analytics .