IT Security Outsourced IT

Security Audit Trail

What is a Security Audit Trail?

A security audit trail, or audit log, is a set of records that collectively provide documentary evidence of processing used to aid in tracing from original transactions forward to related records and reports, and/or backwards from records and reports to their component source transactions.1 While application logs record activity performed by external users, and system logs record activity performed by software, audit trails are exclusively concerned with activities performed by internal users and services on system infrastructure.2 Audit trails typically include:

Application-specific audit trail. Each application records business-relevant events and they are logged in text files or database tables, which simplifies the process of reconstructing the activity history.

Application logs. Application logs are a broad category that include logs that are not necessarily part of the audit trail, such as exception stacktraces and debug messages.

Database logs. Database logs may include logged queries,  change data capture or change tracking functionality, or native audit trail functionality.

Operating system logs. Operating system logs for Linux would include the /var/log/audit/audit.log (or similar files) and /var/log/auth.log. For Windows, operating system logs would include the Windows Event logs for the Security and System groups.

Access logs. Access logs for web servers log internal systems where a source IP address can more easily be mapped to particular users.

Network logs. Network equipment (routers, firewalls) generate a lot of data that may be included in the audit trail.

While audit trails play a critical role in security and compliance, they can be challenging to implement. Some of the challenges include:

Log retention period. Some regulations and certifications specifically require audit logging, requiring log retention for extended time periods in order to satisfy compliance demands. For example, one HIPAA requirement for compliance certification is that a company retain its audit logs for six years. For ISO 27001 certification, companies must store their audit logs for at least three years. Retaining logs for extended periods of time incurs financial costs and also requires resources for maintenance and management.

Correlating audit logs across different systems. Correlating, comparing, and analyzing audit logs across cloud and database vendors for different log formats and protocols can be difficult. Significant time and effort may be required to manage large volumes of logs that require reconciliation. Additionally, discrepancies are common at the level of the details, with the possibility of causing compliance complications.

1 NIST, 2023, “Security Audit Trail”

2 Sharif, 2023, “Audit Logs”