Security information and event management (SIEM) systems are increasingly used to cope with the security challenges involved in critical infrastructure protection. However, these systems have several limitations. This paper describes an enhanced security information and event management system that (i) resolves conflicts between security policies; (ii) discovers unauthorized network data paths and appropriately reconfigures network devices; and (iii) provides an intrusion- and fault-tolerant storage system that ensures the integrity and non-forgeability of stored events. The performance of the enhanced system is demonstrated using a case study involving a hydroelectric dam. The case study considers an attack model that affects portions of the information technology infrastructure of the hydroelectric dam and demonstrates that the security information and event management system is successfully able to detect and respond to attacks.