Access Log

An access log is a time-stamped record of user or system access events captured by an application, operating system, network device, or security tool. In industrial and manufacturing environments, access logs typically track who accessed which system or resource, from where, when, and how.

What an access log typically includes

While formats vary by system, an access log commonly records:

• Identity information: user ID, account name, role, or service account
• Event timing: date and time of login, logout, or resource access
• Source details: device, IP address, or terminal that initiated the access
• Target resource: application, database, file, workstation, PLC, MES transaction, or API endpoint
• Action and outcome: login, logout, read, write, configuration change, success or failure

In regulated manufacturing, access logs are often part of broader audit trail and security logging capabilities across MES, ERP, QMS, data historians, and OT systems.

Operational use in manufacturing and regulated environments

Access logs are commonly used to:

• Support investigations into deviations, data changes, or unexpected process behavior by showing who accessed what and when.
• Demonstrate control over privileged or administrative accounts in production, laboratory, or engineering systems.
• Monitor cybersecurity indicators such as repeated failed logins, unusual access times, or access from unexpected locations.
• Correlate events with other logs (application logs, system logs, change logs) to reconstruct the sequence of actions around an incident.

Access logs may reside on individual devices (for example HMIs, PLC gateways, OT firewalls), in central log management systems, or in security information and event management (SIEM) platforms used across the plant.

What access logs are not

An access log is not:

• A full process history or genealogy record of a part or batch.
• A detailed change log of all data values; instead it focuses on access and session events.
• A substitute for role-based access control; it records activity but does not enforce permissions.

Common confusion

• Access log vs audit trail: An audit trail is a broader record of system and data changes (for example changes to a work instruction, recipe, or quality record). An access log focuses specifically on access and authentication events, though in some systems the terms are used together.
• Access log vs application log: Application logs can include errors, performance information, and business events. Access logs are a specific subset focused on who accessed the application and how.

Relation to compliance and cybersecurity

Access logging is commonly referenced in cybersecurity and data integrity expectations for regulated manufacturing. It supports evidence of:

• Controlled access to MES, QMS, ERP, PLM, and OT assets.
• Monitoring and detection of unauthorized or anomalous access.
• Traceability of user actions linked to changes in critical records or configurations.

Organizations often define retention periods, review practices, and secure storage for access logs to ensure they remain available and tamper-resistant for investigations and audits.