The ELK Stack can be used as a Security Information and Event Management (SIEM) system, but it is not a traditional SIEM itself. It shares common features with SIEMs, such as collecting and querying log data from various sources. However, the ELK Stack requires configuration for real-time security threat detection and may pose challenges for under-resourced teams due to its management complexity, resource intensity, and hidden cost centers like log ingestion and retention. The ELK Stack is not ideal for short-term security workloads, such as real-time threat detection and alerting, but can be used to build a SIEM solution with proper configuration and expertise. Alternative options like modular security data lakes and purpose-built SIEMs may be more suitable for organizations with specific requirements and resources.