Security Monitoring with SIEM Systems
How SIEM systems aggregate logs and detect security threats across your infrastructure.
What Is a SIEM?
A Security Information and Event Management (SIEM) system collects, normalizes, and correlates log data from across your infrastructure — firewalls, servers, applications, endpoints, and network devices. By analyzing events from multiple sources together, a SIEM detects threats that individual systems cannot identify in isolation.
For example, a failed SSH login on one server is routine. But failed SSH logins on 50 servers from the same source IP within 5 minutes indicates a brute-force attack — a pattern only visible with centralized log analysis.
Core SIEM Functions
- Log collection — Agents, syslog, or API integrations forward logs from all sources
- Normalization — Diverse log formats are parsed into a common schema
- Correlation — Rules match patterns across multiple event sources
- Alerting — Triggers notifications for security-relevant events
- Dashboards — Real-time visibility into security posture
- Compliance — Automated reporting for PCI-DSS, HIPAA, SOC 2 requirements
Popular SIEM Solutions
| Solution | Type | Best For |
|---|---|---|
| Wazuh | Open source | SMBs, compliance-driven orgs |
| ELK + Security | Open source | Technical teams, custom workflows |
| Splunk | Commercial | Enterprise, high data volume |
| Microsoft Sentinel | Cloud | Azure-heavy environments |
| CrowdStrike LogScale | Commercial | High-speed search |
Getting Started
Start with critical log sources: authentication systems, firewalls, and DNS servers. Define detection rules for known attack patterns (brute force, impossible travel, privilege escalation). Tune rules iteratively to reduce false positives — an overwhelmed SOC team ignores alerts.
Retention policies matter: keep hot data for 30-90 days for active hunting, and cold storage for 1+ years for compliance and incident response.