Security Monitoring with SIEM Systems

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

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.