In a Security Operations Center (SOC), SIEM (Security Information and Event Management) and log analysis are essential for monitoring, detecting, and responding to security threats. Here are the top 15 questions and answers SOC analysts should know.

Q.1 How does a SIEM system work?

A SIEM system collects security logs and events from multiple sources across the network, including firewalls, servers, endpoints, and applications. It aggregates, normalizes, and correlates the data to detect suspicious activity or security incidents. Analysts can then investigate alerts, visualize trends, and respond to threats efficiently.

Q.2 What types of logs are collected in a SIEM?

SIEM collects various types of logs, such as:

  • System logs: OS events like login attempts or system errors.
  • Network logs: Firewall, router, and switch events.
  • Application logs: Web servers, databases, and custom apps.
  • Security device logs: IDS/IPS, antivirus, and endpoint tools.
  • User activity logs: Login/logout events, access changes, and privilege escalations.

Q.3 What are correlation rules in SIEM?

Correlation rules are patterns defined to detect suspicious behavior across multiple logs. They help identify potential attacks that may not be visible in a single log.

Q.4 How do you reduce false positives in SIEM alerts?

  • Fine-tune correlation rules to match real threats.
  • Use whitelists to ignore trusted IPs or applications.
  • Implement thresholds for event frequency.
  • Continuously review alerts and update SIEM configurations.

Q.5 What is log normalization?

Log normalization standardizes logs from different sources into a consistent format, making them easier to analyze, correlate, and detect threats efficiently.

Example:
A login event from Windows and Linux systems may look different, but normalization converts them into the same structure for SIEM analysis.

Q.6 What are the main log sources in a SOC environment?

Common log sources include:

  • Network devices: Firewalls, routers, switches
  • Servers: Windows, Linux, application servers
  • Endpoints: Laptops, desktops, mobile devices
  • Security tools: EDR, antivirus, IDS/IPS
  • Applications: Web apps, databases, ERP systems

Q.7 What is log retention and why is it important?

Log retention is the process of storing logs for a specific period. It is important for:

  • Forensic investigation: Analyzing past incidents
  • Compliance: Meeting regulatory requirements like GDPR or HIPAA
  • Trend analysis: Detecting patterns and emerging threats

Q.8 What’s the difference between real-time monitoring and historical analysis?

  • Real-time monitoring: Detects and alerts on suspicious activity as it happens.
  • Historical analysis: Examines past logs to identify trends, past attacks, or gaps in defenses.

Both are important: real-time for immediate action and historical for long-term security improvement.

Q.9 What is the use of dashboards in a SIEM tool?

Dashboards visualize data from multiple sources, showing trends, alerts, and key metrics in one place. They help SOC analysts quickly understand the security posture and focus on critical incidents.

Q.10What is an alert threshold?

An alert threshold is the number of times an event must occur before the SIEM generates an alert. It helps reduce false positives and focus on meaningful incidents.

Q.11 What are some common use cases for SIEM alerts?

  • Brute-force login attempts
  • Malware or ransomware detection
  • Privilege escalation attempts
  • Suspicious network traffic or data exfiltration
  • Unusual user behavior (like accessing sensitive files at odd hours)

Q.12 What is event enrichment in SIEM?

Event enrichment adds additional context to logs, such as geolocation of IP addresses, threat intelligence feeds, or user roles, making it easier for analysts to investigate and prioritize alerts.

Q.13 How do you tune correlation rules in a SIEM?

  • Adjust rules to match your network environment and risk profile.
  • Exclude known safe activities using whitelists.
  • Set thresholds for event frequency and severity.
  • Continuously review false positives and adjust the rules for accuracy.

Q.14 What is the purpose of a watchlist or whitelist in SIEM?

  • Watchlist: Monitors specific entities like high-risk users, IPs, or devices.
  • Whitelist: Excludes trusted entities from triggering alerts, reducing false positives.

Q.15 What is threat intelligence integration in SIEM?

Integrating threat intelligence feeds into SIEM provides real-time indicators of compromise (IoCs) like malicious IPs, domains, and file hashes. This helps SOC analysts detect known threats faster and respond proactively.

Conclusion

SIEM and log analysis are the backbone of SOC operations. Understanding log sources, correlation rules, dashboards, and threat intelligence integration allows SOC analysts to detect, investigate, and respond to cyber threats efficiently. Proper tuning, normalization, and retention of logs ensure accurate alerts, reduced false positives, and faster incident response.