What Exactly Should We Be Logging? A Structured Guide for Security Professionals

In the ever-evolving landscape of cybersecurity, logging is a cornerstone of effective security monitoring and incident response. But what exactly should we be logging, and when should we collect this data? This article provides a structured look at the critical data to collect for security purposes, offering actionable insights for Red Teamers, Blue Teamers, SOC Analysts, Threat Intel Researchers, and System Administrators.

TL;DR: Key Takeaways

Purpose of Logging: Logs are essential for troubleshooting, auditing, and detecting security incidents.
Core Elements to Log: Functional correctness, performance, reliability, and security-related data.
Best Practices: Use structured logging, avoid sensitive data, and centralize logs for efficient analysis.
Audience Relevance: Tailor logs to meet the needs of security teams, ensuring they provide actionable insights.
Remediation Tips: Regularly review logging strategies and ensure logs are machine-parseable and human-readable.

The Importance of Logging in Cybersecurity

Logging is more than just a record of events; it’s a critical tool for understanding system behavior, detecting anomalies, and responding to incidents. For security teams, logs provide the forensic evidence needed to trace attacks, identify vulnerabilities, and ensure compliance with regulatory requirements. However, without a clear strategy, logging can become overwhelming, leading to “log fatigue” and missed threats.

What Should We Log?

Functional Correctness

Functional correctness ensures that a system performs as expected. Logs should capture:

Operational Correctness: Whether the system executed the expected operations.
Data Correctness: Whether the system consumed and produced the expected data.

For example, if a payment system charges a credit card, logs should confirm the charge was processed correctly and the correct amount was deducted.

Performance

Performance logs help identify bottlenecks and ensure systems operate efficiently. Key metrics include:

Latency: Time taken to service a request.
Throughput: Number of requests serviced per second.

Reliability

Reliability logs track system failures and their causes. Key questions to answer include:

Failure Rate: How often does the system fail?
Failure Path: What components were involved in the failure?

Security

Security logs are critical for detecting and responding to threats. They should capture:

Operational Compliance: Whether operations comply with security requirements.
Data Compliance: Whether data handling meets security standards.

For instance, logs should record authentication attempts, access requests, and any changes to sensitive data.

Best Practices for Effective Logging

Structured Logging: Use formats like JSON to make logs machine-parseable and human-readable.
Avoid Sensitive Data: Never log passwords, credit card numbers, or personally identifiable information (PII).
Centralized Logging: Aggregate logs from multiple sources into a single platform for easier analysis.
Log Levels: Use appropriate log levels (e.g., INFO, WARN, ERROR) to categorize events by severity.
Contextual Logging: Include context such as user IDs, request IDs, and timestamps to make logs actionable.

Relevance to Security Teams

For Red Teamers

Red Teamers can use logs to simulate attacks and identify gaps in logging coverage. For example, if an attack vector isn’t logged, it’s a blind spot that needs addressing.

For Blue Teamers and SOC Analysts

Blue Teamers rely on logs to detect and respond to incidents. Centralized logging and structured formats enable faster correlation of events and more effective threat hunting.

For System Administrators

System Administrators use logs to monitor system health and performance. By logging key metrics, they can proactively address issues before they escalate.

Remediation and Tips

Regular Audits: Periodically review logs to ensure they meet security and compliance requirements.
Automated Alerts: Set up alerts for critical events, such as failed login attempts or unauthorized access.
Log Retention Policies: Define how long logs should be retained based on regulatory and operational needs.

Conclusion

Effective logging is a balancing act: too little, and you miss critical insights; too much, and you drown in noise. By focusing on functional correctness, performance, reliability, and security, and adhering to best practices, security teams can ensure their logs are both useful and manageable. As threats evolve, so too should our logging strategies, ensuring they remain a powerful tool in the fight against cybercrime.