What a SIEM Does and Why It Matters for OT
A Security Information and Event Management (SIEM) platform performs three core functions: log aggregation (collecting events from disparate sources into a central repository), correlation (applying detection rules that match patterns across multiple events in time), and alerting (notifying analysts when a correlation rule fires). Without a SIEM, an analyst investigating a suspected intrusion must manually query firewall logs, Active Directory event logs, and historian alarm logs separately — a process that takes days. A SIEM makes cross-source queries instantaneous and enables automated detection of multi-stage attack sequences that no single log source would reveal.