Complete SIEM Guide 2024: Security Information & Event Management

Key Takeaways

SIEM collects, normalizes, and correlates security logs.
Proper use cases reduce alert fatigue.
Log sources quality determines SIEM effectiveness.

Tuning rules is ongoing work, not one-time setup.
SOAR adds automation to SIEM workflows.
Modern SIEMs integrate UEBA and threat intelligence.

1. What is SIEM?
2. SIEM Architecture
3. Log Sources
4. Detection Rules & Use Cases

5. Tuning & Optimization
6. SIEM Platforms
7. SIEM Evolution
8. Frequently Asked Questions

1. What is SIEM?

Security Information and Event Management (SIEM) is a technology that collects and aggregates log data from across an organization's infrastructure, normalizes it into a common format, correlates events to detect security threats, and provides alerting, dashboards, and reporting capabilities.

SIEM is the foundation of Security Operations Centers (SOC), enabling analysts to monitor the environment, investigate incidents, and meet compliance requirements through centralized logging and reporting.

SIEM Core Functions

Collection: Gather logs from all sources
Normalization: Convert to common format
Correlation: Identify patterns across events
Alerting: Notify on detected threats
Retention: Store for investigation and compliance

2. SIEM Architecture

2.1 Components

Collectors/Agents: Gather logs from endpoints and network devices
Log Management: Centralized storage and indexing
Correlation Engine: Applies detection rules
Dashboard: Visualization and investigation interface
Reporting: Compliance and executive reporting

2.2 Deployment Models

Model	Pros	Cons
On-Premises	Full control, data sovereignty	High maintenance, scaling challenges
Cloud-Native	Scalability, lower maintenance	Data transfer costs, vendor lock-in
Hybrid	Flexibility	Complexity, multiple tools

3. Log Sources

3.1 Critical Log Sources

# Essential logs for security monitoring:
- Windows Event Logs (Security, System, Application)
- Active Directory / Azure AD
- Firewall logs
- VPN logs
- Endpoint Detection & Response (EDR)
- Web proxy / URL filtering
- Email gateway
- Cloud services (AWS CloudTrail, Azure Activity Log)
- DNS queries
- DHCP leases
- Application logs

3.2 Log Collection Methods

Syslog: Standard protocol for network devices
Agents: Software installed on endpoints
API: Pull from cloud services
WEC: Windows Event Collection

4. Detection Rules & Use Cases

4.1 Common Use Cases

Use Case	Detection Logic
Brute Force	5+ failed logins in 5 minutes
Impossible Travel	Logins from distant locations in short time
Privilege Escalation	User added to admin group
Data Exfiltration	Large outbound transfers to new destinations
Malware	Known bad hashes, C2 domains

4.2 Correlation Rule Example

# Splunk SPL - Failed login followed by success
index=windows EventCode=4625 
| stats count by src_ip, user 
| where count > 5 
| join src_ip [search index=windows EventCode=4624]
| table src_ip, user, count

Alert Fatigue

More alerts ≠ better security. Too many false positives cause analysts to ignore or miss real threats. Focus on high-fidelity detections. It's better to have 10 actionable alerts than 1000 noisy ones.

5. Tuning & Optimization

Whitelist known-good activities (scheduled scans, admin tools)
Tune thresholds based on baseline behavior
Add context to alerts (asset criticality, user role)
Regular false positive review and rule adjustment
Prioritize rules that map to your threat model

6. SIEM Platforms

Platform	Type	Best For
Splunk	Commercial	Enterprise, extensive capabilities
Microsoft Sentinel	Cloud	Microsoft environments, Azure
IBM QRadar	Commercial	Enterprise, compliance
Elastic SIEM	Open Source	Cost-conscious, skilled teams
Google Chronicle	Cloud	Large data volumes, Google ecosystem

7. SIEM Evolution

7.1 Modern Capabilities

UEBA: User and Entity Behavior Analytics—ML-based anomaly detection
SOAR: Security Orchestration, Automation and Response—automated playbooks
XDR: Extended Detection and Response—unified across endpoint, network, cloud
Threat Intelligence: Integrated IoC feeds and enrichment

MITRE ATT&CK Mapping

Align your detection rules with MITRE ATT&CK framework. This helps identify coverage gaps and prioritize detections based on adversary techniques most relevant to your environment.

8. Frequently Asked Questions

How long should I retain logs?

Depends on compliance requirements and investigation needs. Common: 90 days hot storage for active investigation, 1 year cold storage for compliance. Some regulations require longer (7 years for financial). Balance cost with requirements.

SIEM vs XDR—which do I need?

SIEM provides broad visibility and compliance. XDR offers deeper, more integrated detection across specific platforms. Many organizations use both: SIEM for log management and compliance, XDR for advanced threat detection on key assets.

Conclusion

SIEM is essential for security visibility, threat detection, and compliance. Success requires quality log sources, well-tuned detection rules, and skilled analysts. Invest in tuning and contextualization to combat alert fatigue. Modern SIEM increasingly incorporates UEBA, SOAR, and threat intelligence for more effective detection and response.

Continue Learning:
Incident Response SOC Analyst Guide