I've found that microservices bring flexibility and speed, but each service also introduces a new attack surface, making security in a distributed system more challenging than in a monolith
When securing microservices on Azure, I prioritize understanding the main threats, such as injection attacks, which target API endpoints and can be mitigated by validating every input and using an API gateway
Broken access control is another key concern, where each service needs its own identity and permissions, and using OAuth 2.0 for consistent access control and following the principle of least privilege is essential
Data interception is also a risk, as data moving between services can be intercepted or tampered with, and enforcing TLS for all inter-service communication and storing cryptographic keys in Azure Key Vault can help
Distributed systems can amplify the impact of DDoS attacks, and using rate limiting, traffic shaping, and Azure DDoS Protection, as well as autoscaling, can help absorb traffic spikes
Azure provides several tools to help with security, including AKS security features like network policies, RBAC, and Azure Policy integration, which should be used to secure containerized applications
Azure API Management is another useful tool, as it centralizes authentication, authorization, rate limiting, and analytics for APIs, providing visibility into usage patterns and helping to catch anomalies
Application Gateway WAF can block common attacks like SQL injection, XSS, and CSRF before they reach services, and Azure Monitor and Defender for Cloud can aggregate telemetry and set up alerts to help detect and respond to security incidents
In terms of development practices, container security is crucial, and scanning images in Azure Container Registry before deployment, running with minimal permissions, and using AKS admission controllers can help enforce runtime policies
Immutable infrastructure and DevSecOps practices, such as defining infrastructure in code, using blue-green or canary deployments, and including security checks in the CI/CD pipeline, can also help reduce exposure and catch issues early