Audit logs answer the questions every investigation, auditor and board eventually asks: who did what, when, where, and did it succeed? Done well, they're the backbone of security, compliance and accountability. Done badly, they're expensive noise.
What is audit logging?
Audit logging records security-relevant actions taken by users and systems: sign-ins, permission changes, data access, configuration changes and deletions. Unlike application logs, which describe how software behaves, audit logs describe what people and services did.
Four components of an effective audit log entry
- Actor: the user, service account or system responsible, for attribution.
- Action: what was done, using clear verbs such as created, modified, deleted or granted.
- Timestamp: when it happened, in a consistent, synchronised time zone, for reliable timelines.
- Context and outcome: source IP, device, affected resource and whether the action succeeded or failed.
Audit logs vs application logs
| Audit logs | Application logs | |
|---|---|---|
| Purpose | Compliance, detection, investigations | Troubleshooting and performance |
| Audience | Security, audit, legal | Developers and SRE |
| Retention | Months to years, often regulated | Days to weeks |
| Integrity | Must be tamper-evident | Best effort |
Because their purpose, audience and retention differ, store them separately and route them differently in your security data pipeline.
Why audit logging matters
- Security: spots suspicious or unauthorised activity early.
- Compliance: supports ISO 27001, SOC 2, GDPR, India's CERT-In directions, Saudi NCA ECC and Qatar's NIAS v2.1.
- Accountability: ties every sensitive action to a specific actor and time.
Six audit logging best practices
- Separate audit logs from application logs, so operational noise can't bury security records.
- Standardise and make logs immutable, with a common schema and tamper-evident storage for forensic admissibility.
- Minimise data: never log secrets or passwords, and mask personal data you don't need.
- Plan for scale with tiered retention in a security data lake.
- Centralise audit logs in a SIEM or log platform so investigators can correlate events.
- Restrict access to audit logs, and log access to the logs themselves.
Common challenges
- Volume overload: too many events hide the important ones. Filter and tier.
- Performance impact: synchronous logging can slow applications. Use asynchronous pipelines.
- Inconsistent formats: different shapes break correlation. Adopt a common schema early.
Frequently asked questions
How long should audit logs be kept?
It depends on your regulators and contracts. Many frameworks expect at least 12 months, and financial and government records often need several years. Keep recent logs searchable and older logs in an immutable archive.
Should audit logs go into the SIEM?
Security-relevant audit events, such as privileged actions, failed access and permission changes, should. Bulk audit history can live in a lower-cost data lake or archive with recall into the SIEM when needed.