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Log Analysis Basics

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Mahesh Shukla edited this page Aug 8, 2025 · 2 revisions

Overview

Logs are detailed records created by computers, servers, and network devices that track events and activities. For SOC analysts, analyzing these logs is crucial to understand what’s happening within an environment, detect potential security threats, and troubleshoot issues effectively.

Common Log Sources

  • Firewalls: Monitor network traffic, controlling which connections are allowed or blocked.
    Example: A firewall log might show a blocked connection attempt from an unknown IP address.

  • Servers: Record activities on web servers, application servers, and databases.
    Example: Server logs can capture failed login attempts or application errors.

  • Endpoints: Include laptops, desktops, and mobile devices, logging user actions and system events.
    Example: Endpoint logs might reveal a suspicious program execution or unauthorized file access.

Types of Logs and Their Information

  • Event Logs: Track general system events like logins, shutdowns, or errors.
    Example: A successful user login or system restart.

  • Audit Logs: Capture security-relevant actions such as changes to user permissions or access to sensitive data.
    Example: A user changing their password or accessing confidential files.

  • Network Logs: Generated by firewalls, IDS/IPS, or proxies to record network traffic and suspicious activities.
    Example: Detection of an unusual data transfer outside business hours.

  • Application Logs: Contain details about application behavior, errors, and user activities.
    Example: A failed transaction on a web application.

How to Read and Interpret Logs

  • Identify Key Details: Focus on timestamps, source/destination IPs, usernames, and event descriptions.
    Example: An alert showing a login from a foreign IP at an unusual time.

  • Correlate Events: Link related logs across different sources to get a complete picture.
    Example: Failed login attempts followed by a successful login from the same user on a different machine.

  • Spot Anomalies: Look for unusual patterns such as repeated failed logins, unexpected processes, or data transfers.
    Example: Multiple failed logins from the same user in a short time frame.

  • Use Tools Effectively: Leverage SIEM systems and log aggregators to filter, search, and visualize logs for faster analysis.

Importance of Log Management and Retention

  • Retention Policies: Keep logs for a defined period to support investigations and compliance requirements.
    Example: Storing logs for one year to comply with industry regulations.

  • Integrity: Ensure logs cannot be tampered with to maintain trustworthy evidence.
    Example: Using write-once storage or cryptographic hashing.

  • Storage & Scalability: Manage large volumes of log data efficiently, often using cloud or centralized storage solutions.

  • Access Control: Restrict log access to authorized personnel only, maintaining confidentiality and preventing misuse.

Summary

Log analysis is foundational for any SOC analyst. Understanding where logs come from, what information they contain, and how to interpret them is essential for detecting security incidents and maintaining a secure environment. Proper log management ensures data integrity, availability, and compliance — all critical to effective cybersecurity operations.

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