Question

When a SIEM system aggregates logs from diverse sources, what specific process does it perform to identify a complex attack that spans multiple devices?

Accepted Answer

The specific process a SIEM system performs to identify a complex attack spanning multiple devices is called correlation. Correlation is the logical linking of related events from different sources to detect patterns that suggest a coordinated threat. Because individual devices generate thousands of logs that look normal in isolation, the SIEM system uses correlation rules to compare logs across the entire network infrastructure. A correlation rule is a predefined logic statement that looks for a sequence of events occurring within a specific timeframe across different log sources. For example, a system might flag a brute force attack by correlating three failed login attempts on a workstation, followed by a successful login on a server, and finally a large data transfer to an external IP address. The SIEM system normalizes the data first, which means converting raw, messy log formats from different vendors into a single standardized format so they can be compared. Once the data is normalized, the correlation engine processes the events against its active rules. When the system detects a sequence that matches the defined rule criteria, it triggers an alert, enabling security analysts to see the full scope of an attack that would otherwise remain hidden within disconnected data silos.

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When a SIEM system aggregates logs from diverse sources, what specific process does it perform to identify a complex attack that spans multiple devices?