Key takeaways

• Shadow APIs are undocumented, while zombie APIs are deprecated but still accessible.
• Manual discovery and documentation can’t keep pace with the velocity of API creation and modification in development.
• Automated API discovery provides continuous visibility and reliable validation.
• Invicti combines agentless API discovery with proof-based runtime vulnerability testing and reporting on a centralized AppSec platform.

Hidden APIs are among the most persistent blind spots in modern application environments. With so many interconnected services being developed and modified so rapidly, it’s easy for undocumented or deprecated APIs to remain active and expose sensitive data. Shadow and zombie APIs quietly expand your attack surface, making automated discovery and validation essential to maintain both visibility and control.

Understanding shadow and zombie APIs

Shadow APIs are undocumented or unmanaged endpoints that operate outside official inventories. Zombie APIs are deprecated or outdated interfaces that remain accessible in production even after being replaced. Both types are often invisible to standard monitoring and can introduce security and compliance risks.

Learn about the differences between shadow, zombie, and rogue APIs

How hidden APIs emerge

Shadow APIs appear when development teams deploy new features, microservices, or test environments without updating documentation or notifying security. Similarly, zombie APIs persist when old versions of endpoints are never fully retired, leaving them reachable through legacy integrations or direct calls. Limited lifecycle management, inconsistent documentation, and fragmented ownership all contribute to these issues.

Why hidden APIs matter

Every hidden or forgotten API increases potential exposure. Shadow APIs may bypass security controls or handle sensitive data that was never assessed, while zombie APIs may still accept requests using outdated logic or weaker authentication. Both make it difficult to meet regulatory requirements that depend on accurate asset inventories and risk tracking.

Why traditional discovery methods miss hidden APIs

Manual API inventories quickly become obsolete as applications evolve. Penetration tests and static reviews only evaluate known assets and documented endpoints. Traditional methods also depend on dev teams maintaining fully accurate documentation – something that’s rarely a reality at an enterprise scale. Without centralized oversight, APIs deployed in cloud or third-party environments often go untracked.

How to detect shadow APIs automatically

Most API discovery tools rely solely on agent-based methods, where network sensors or monitoring agents are deployed to observe traffic across environments. While this approach can provide deep insights, it also introduces considerable complexity. Deploying and maintaining agents across distributed and containerized systems takes time, adds operational overhead, and can still leave blind spots in cloud-native or hybrid environments where traffic isn’t fully captured.

Invicti takes a different approach to API security. Its platform combines sensorless (agentless) API discovery through dynamic application security testing (DAST) with optional agent-based network traffic analysis (NTA). The sensorless method uses DAST scans to generate real application traffic and automatically infer API endpoints and operations based on live interactions, with no agents or special network access required. This enables fast, scalable API discovery with minimal setup while still offering the option to deploy NTA for more detailed network-level visibility when needed.

During scanning, Invicti’s DAST engine observes and analyzes API calls made by the application in real time, reconstructing specifications directly from live behavior. The discovered endpoints can then be compared against official OpenAPI or Swagger documentation to identify discrepancies. Any active endpoints not represented in the documentation are likely shadow APIs that require review or governance. This combined approach delivers both breadth and depth, with broad coverage from sensorless discovery and fine-grained analysis from NTA where needed.

How to detect zombie APIs automatically

Once shadow APIs have been identified, the next challenge is finding zombie APIs – deprecated or outdated endpoints that remain active in production. Because Invicti’s discovery process continuously captures live traffic and compares it to known documentation, it can also highlight APIs that are still responding even though they’ve been retired or replaced in official specifications.

This continuous visibility is especially valuable when paired with Invicti’s dual discovery model. The sensorless DAST-based scans can detect zombie endpoints that remain publicly accessible but undocumented, while optional NTA agents can confirm whether those APIs are still being called internally. Together, these methods allow teams to spot inactive or obsolete APIs before attackers do. Over time, automated scans and documentation comparisons ensure that deprecated endpoints are surfaced early, allowing organizations to remove or secure them before they become liabilities.

Benefits of automated API discovery and scanning

Automated discovery and scanning provide ongoing visibility into how APIs actually operate across all environments. The main benefits include:

• Continuous visibility into active and hidden APIs
• Faster identification of untracked endpoints and exposed interfaces
• Reduced likelihood of data leaks and compliance failures
• Proof-based validation to confirm exploitable vulnerabilities and minimize false positives

By combining runtime discovery and proof-based validation, Invicti helps teams focus on verified, actionable issues rather than unconfirmed findings.

Invicti’s approach to detecting hidden APIs

Invicti extends automated API discovery beyond simple endpoint detection by combining dynamic API vulnerability scanning, validation, and centralized visibility within a single platform. Its DAST-first design means the same scans that uncover APIs can also test them for vulnerabilities in real time to create a continuous feedback loop between discovery and security validation.

Because Invicti’s sensorless discovery is built into its core scanning engine, it can reveal APIs without requiring dedicated monitoring infrastructure. This capability not only identifies shadow and zombie APIs but also allows the platform to assess their security posture immediately using proof-based scanning. Many vulnerabilities found during scanning can be automatically confirmed as exploitable, giving teams verified results they can act on with confidence.

At the enterprise level, Invicti’s integration with application security posture management (ASPM) brings these insights into a unified view. Security and development teams can correlate API discovery results, validated vulnerabilities, and risk scores across applications, enabling clear prioritization and compliance reporting. The result is practical, scalable visibility into the full API landscape, from discovery through validation to remediation tracking, all without adding unnecessary operational complexity.

Business outcomes of automated API detection

Automated API detection delivers measurable improvements across both security and operational performance. By maintaining accurate and continuously updated API inventories, organizations gain full visibility into what is actually exposed in production. This clarity strengthens compliance by providing auditable records of APIs, their purpose, and their security status. It also reduces the risk of breaches linked to forgotten or undocumented endpoints and helps teams identify and address exposure before it can be exploited.

The operational benefits are equally significant. Automated discovery and proof-based validation allow security and development teams to focus on verified issues, cutting down the time spent chasing false positives or manually updating documentation. With faster detection and clearer prioritization, organizations can remediate issues earlier in the lifecycle for reduced cost and effort. The result is a stronger, more predictable application security posture that executives can trust, supported by data-driven insight rather than assumptions.

Conclusion: Bring your hidden APIs into view and under control

You can’t protect what you can’t see. Shadow and zombie APIs often emerge unnoticed as applications evolve, but automation brings them into focus. Invicti’s DAST-first, proof-based approach to API discovery and testing helps organizations maintain accurate visibility and validate real risks efficiently.

See how Invicti helps uncover shadow and zombie APIs automatically with sensorless discovery – schedule a demo today.