Logging is not about recording what happened—it is about creating forensic evidence of system behavior that auditors, incident responders, and security analysts can examine. ISO/IEC 27001 Control A.8.15 explicitly requires that “event logs recording user activities, exceptions, faults and information security events shall be produced, kept and regularly reviewed.”
Most developers approach logging as an afterthought: simple string formatting that produces unstructured, unsearchable log files. Compliance requires something different: semantically rich logs with standardized fields, user identifiers, action context, and outcomes that can be correlated across system components.
Structured Logging in .NET
Structured logging captures data as semantic properties, not text strings. Using libraries like Serilog or the built-in ILogger with Application Insights enables querying logs by field, correlating events across services, and automatically alerting on security anomalies. Logging architecture becomes part of security architecture.
Critical considerations: never log sensitive data (credentials, payment tokens, personal information), include sufficient context to understand user actions, correlate requests across distributed systems, and monitor for suspicious patterns (repeated authentication failures, unauthorized access attempts, data exfiltration indicators).