Prometheus and Alertmanager are critical components of modern monitoring stacks, widely adopted for their powerful metrics collection and alerting capabilities. However, their default configurations often lack built-in strong security features, making them vulnerable to unauthorized access and data breaches. This blog dives into best practices for securing Prometheus and Alertmanager focusing on authentication, authorization, and encryption, tailored for intermediate and advanced users who want to safeguard their monitoring environment.

Why Security Matters for Prometheus and Alertmanager

Prometheus collects sensitive operational data, including application and infrastructure metrics, while Alertmanager manages critical notifications. Unauthorized access can lead to data leakage, tampering, or disruption of alerting workflows, resulting in severe operational risks.

Key security goals include:

  • Ensuring only authorized users and systems can query metrics or modify alert rules
  • Protecting data in transit from interception or tampering
  • Enforcing least privilege access controls to reduce attack surface

Authentication Strategies

By default, Prometheus and Alertmanager do not include native authentication mechanisms. It is crucial to implement external solutions to authenticate users and services.

1. Reverse Proxy Authentication
Use a reverse proxy like NGINX or Traefik in front of Prometheus and Alertmanager to enforce authentication. Common approaches include:

  • Basic Authentication: Simple username/password but should be combined with HTTPS
  • OAuth2 / OpenID Connect: Integrate with identity providers like Keycloak, Google, or Azure AD for single sign-on (SSO) and centralized user management
  • Client Certificate Authentication: For mutual TLS (mTLS), clients present certificates to verify identity

2. Prometheus Remote Write Authentication
When using remote write endpoints or federation, secure communication by configuring authentication tokens or TLS client certificates to prevent unauthorized data ingestion.

Authorization Best Practices

Authentication verifies identity, but authorization controls what authenticated users can do.

1. Role-Based Access Control (RBAC)
Although Prometheus lacks built-in RBAC, consider these options:

  • Proxy-level RBAC: Implement role-based rules in the reverse proxy layer to restrict endpoints based on user roles. For example, allow read-only queries for developers and full write/modify access for admins.
  • Kubernetes RBAC: If running Prometheus inside Kubernetes, leverage Kubernetes RBAC to restrict access to Prometheus API endpoints exposed via the Kubernetes API server or ingress controllers.

2. Alertmanager Silencing and Routing Policies
Configure Alertmanager’s routing tree carefully to ensure sensitive alerts only reach authorized teams. Use silences sparingly and audit their usage regularly.

Encryption Techniques

Securing data in transit is paramount to protect monitoring data from eavesdropping and man-in-the-middle (MITM) attacks.

1. TLS Encryption for HTTP Endpoints
Enable TLS for Prometheus and Alertmanager web UIs and APIs. If they do not natively support TLS termination, terminate TLS at the reverse proxy layer.

2. Mutual TLS (mTLS)
For enhanced security, configure mutual TLS between Prometheus and Alertmanager or other components in your stack. This ensures both client and server validate each other’s certificates.

3. Encrypting Remote Write and Federation Traffic
Always use TLS when configuring remote write or federation between Prometheus servers to secure metric data in transit.

Additional Security Enhancements

1. Network Policies & Firewall Rules
Restrict network access to Prometheus and Alertmanager services using Kubernetes Network Policies, security groups, or firewall rules to limit exposure only to trusted IPs or namespaces.

2. Regularly Update and Patch
Keep Prometheus, Alertmanager, and all related components up to date to patch known vulnerabilities.

3. Audit Logging and Monitoring
Enable access logs on reverse proxies and monitor unusual access patterns. Integrate logs with centralized logging and SIEM tools for real-time alerting on suspicious activity.

Conclusion

Securing Prometheus and Alertmanager requires a multi-layered approach combining authentication, authorization, and encryption. Leveraging reverse proxies for authentication, implementing RBAC at the proxy or orchestration layer, and enforcing TLS and mTLS across all communication channels will dramatically reduce risk and protect your monitoring infrastructure. For advanced users, integrating these practices with Kubernetes security features and continuous monitoring ensures a robust and compliant observability platform.

Adopting these best practices not only strengthens your security posture but also ensures reliable and trusted monitoring essential for modern DevOps and SRE workflows. Start implementing these strategies today to safeguard your Prometheus and Alertmanager setup effectively.