Security Information and Event Management (SIEM) systems aggregate and correlate security-relevant logs across your infrastructure — this guide covers building basic SIEM-style capability on a self-hosted VPS.
What SIEM Provides
Centralized collection of security-relevant events (authentication, access, system changes) from across your infrastructure, with correlation and alerting capability — the goal is detecting security-relevant patterns that individual, siloed logs wouldn't reveal.
Building Blocks You Likely Already Have
See How to Set Up Centralized Logging with the ELK Stack (Elasticsearch, Logstash, Kibana) or How to Set Up Centralized Logging with Grafana Loki — these general-purpose centralized logging platforms can serve as the foundation for basic SIEM-style capability, with security-specific configuration layered on top.
What Security-Relevant Logs to Centralize
- Authentication events (SSH, application login, sudo usage) — see How to Monitor Auth Logs and Detect Intrusion Attempts on a Linux VPS
- Firewall logs (blocked/allowed connections)
- Application-level audit logs (see How to Set Up Audit Logging for Compliance Requirements)
- File integrity monitoring alerts (see How to Set Up File Integrity Monitoring with AIDE)
- auditd events (see How to Install and Configure auditd for System Auditing)
Building Correlation Rules
Beyond just collecting logs, genuine SIEM value comes from correlation — detecting patterns across multiple log sources (e.g. a failed SSH login followed shortly by a successful one from a different, unfamiliar IP) that individual logs alone wouldn't flag as suspicious.
Example Correlation: Multiple Failed Logins Followed by Success
# Conceptual Loki/LogQL example
{job="auth"} |= "Failed password" | count_over_time[5m] > 5
and
{job="auth"} |= "Accepted password" [5m]A simplified illustration of the correlation concept — actual implementation depends on your specific logging platform's query/alerting capabilities.
Setting Up Alerts for Security-Relevant Patterns
See How to Set Up Effective Server Alerting (Without Alert Fatigue) — configure specific alerts for genuinely security-relevant patterns (privilege escalation, unusual access times, geographic anomalies for access) distinct from general operational alerting.
Retention Requirements for Compliance
See How to Set Up Audit Logging for Compliance Requirements and specific compliance framework guides — security logs often have specific minimum retention requirements under various compliance frameworks; verify your retention policy meets applicable requirements for your situation.
Ensuring Log Integrity
Security logs themselves need protection from tampering — see the tamper-evidence considerations in How to Set Up Audit Logging for Compliance Requirements, ensuring an attacker who compromises a system can't simply erase evidence of their activity from centralized logs.
Commercial SIEM vs Self-Built
Dedicated commercial SIEM platforms offer more sophisticated built-in correlation, threat intelligence integration, and compliance reporting than a self-assembled solution — weigh this against cost and your team's capacity, similar to other self-hosted vs managed trade-offs throughout this Knowledge Base.
Starting Simple and Expanding
Begin with centralizing the most critical security logs and basic alerting, expanding correlation sophistication over time as you understand your actual threat patterns and false-positive rates — don't attempt to build comprehensive SIEM capability all at once.
Continue Reading
- How to Set Up Centralized Logging with the ELK Stack (Elasticsearch, Logstash, Kibana)
- How to Set Up Audit Logging for Compliance Requirements
- How to Monitor Auth Logs and Detect Intrusion Attempts on a Linux VPS
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