Moving from a monolithic architecture to a modern microservices-based application is a transformative change. It’s not just a shift—it’s a seismic overhaul. To make this transition, teams need to rethink how applications are built, deployed, and secured. Developers must focus on breaking monolithic applications into smaller, self-contained services. Operations teams need to establish new frameworks for managing containerized environments and orchestrating services using tools like Kubernetes. Meanwhile, DevOps engineers must adapt CI/CD pipelines to accommodate the complexities of hundreds of independently deployable components. In short, this evolution demands a steep learning curve for everyone involved.
At the heart of microservices lies the need for precise implementation and deployment. Microservices are independently deployable units, often tailored to perform specific functions. Unlike traditional monolithic applications, where all components are interdependent, microservices operate as distinct services within a "logical" application ecosystem. This approach not only enables cutting-edge technologies like AI and ML but also provides a foundation for creating scalable, cost-effective software. The journey to microservices is undoubtedly challenging, but the benefits make it worthwhile.
However, such a significant shift introduces unique challenges, particularly regarding security. With microservices, the attack surface grows exponentially. Code-level vulnerabilities within individual services can propagate across the entire ecosystem, compromising the logical application. These vulnerabilities demand a granular approach to security—one that ensures each microservice is resilient against exploitation.
While there are many discussions your organization will need to have about microservices, it's critical to focus on these three basic truths—and the security implications they introduce:
1) Microservices do not require a traditional ‘build’ step. Linking and dependency resolution occurs at runtime via APIs, exposing your system to potential vulnerabilities from loosely coupled integrations.
2) To fully benefit from microservices, they should be shared across teams, which means a single vulnerability could impact multiple applications. A clear understanding of a service's consumers and where it is deployed is essential for quickly responding to new CVEs.
3) Microservices are independently deployed and can impact multiple ‘logical’ applications. Generating the critical Software Bill of Material report is done for every microservice, not a 'logical' application. Aggregating security insights to the application level is required to secure the application as a complete solution.
The CI Build
In a monolithic architecture, the CI build consolidates code, dependencies, and libraries into a single unit. This process defines application behavior, security, and dependencies as a whole. With microservices, this paradigm shifts. Each microservice—often just a few hundred lines of code—is built and packaged as a container image, then pushed to a container registry. However, the “linking” step no longer happens during the build; it happens at runtime via APIs, making it more difficult to understand a service's blast radius.
This runtime linking introduces new risks. Microservices that depend on external APIs or shared services may unknowingly inherit vulnerabilities, including insecure API implementations, outdated libraries, or unvetted container dependencies. Security must now extend to ensuring each microservice is hardened against exploitation and carefully tested for vulnerabilities in isolation, as well as within the broader runtime ecosystem on a continuous, not static, basis. The need for continuous vulnerability management increases along with the complexities of dependency relationships across the organization's digital assets.
Microservice Sharing and Domains
Reusing microservices across teams is a hallmark of microservice architecture, but it also increases exposure to code-level vulnerabilities. Poorly managed microservices, or what’s known as “microservice sprawl,” can lead to fragmentation and duplication, making it harder to patch or secure critical components.
A Domain-Driven Design (DDD) approach helps address this issue by grouping microservices into logical "solution spaces" that align with business domains. With proper domain identification, up to 80% of microservices can be reused, reducing the attack surface while maintaining consistency. However, shared microservices require robust security policies, including regular vulnerability scanning, dependency tracking, and proactive patching, to ensure that a vulnerability in one domain does not cascade into others.
The Loss of the ‘Logical’ Application
One of the most disruptive aspects of microservices is the loss of the monolithic application build and versioning processes. While microservices eliminate the need for a centralized application release, they introduce complexity in tracking the logical application—a collection of interconnected services working together.
Without a clear view of how microservices interact, organizations risk missing critical vulnerabilities that may arise from insecure integrations or incompatible versions. To mitigate this, modern tools and practices are needed for tracking and managing service versions, dependencies, and configurations. Visualizing the logical application and understanding its composition are essential for maintaining security, especially as microservices scale across multiple teams and environments.
Conclusion
Adopting a Kubernetes and microservices architecture is a critical step toward future-proofing your organization. However, this transition comes with significant security challenges, especially regarding code-level vulnerabilities.
Recognize the shift from a monolithic build to runtime API linking, and establish rigorous testing and security protocols for each microservice.
Define microservice patterns within logical domains to prevent sprawl, ensure reuse, and maintain consistent security practices.
Implement robust tools and practices to track microservice versions, dependencies, and their impact on logical applications, enabling effective security and configuration management at scale.
Ultimately, securing a microservice architecture requires not only reimagining software development practices but also embedding security into every step of the process, from containerization to runtime execution. Only by addressing these challenges can organizations achieve the scalability, flexibility, and security demanded by modern microservices-driven applications.
About the Author
About the Author
Tracy is the CEO and Co-Founder of DeployHub, the first continuous vulnerability management platform designed to accelerate patch management and create a digital immune system, enabling software to self-heal. She is an expert in DevSecOps pipelines, software supply chain security, and decoupled architectures.
Tracy serves as a board member of the OpenSSF, where she is the elected General Member Representative. She is also the Deputy Co-Chair of the Continuous Delivery Foundation (CDF) Technology Oversight Committee. Additionally, she is the Executive Director of the Ortelius Open Source Project, an open-source vulnerability management solution incubating at the CDF.
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