API Discovery: 4 Types of APIs and the 4-Step Discovery Process

• Managed APIs: APIs that are properly documented, secured, and controlled by the organization.
• Shadow APIs: Undocumented or unauthorized APIs deployed without formal IT oversight. They pose significant security and compliance risks because they are not properly managed.

• Zombie APIs: Older, deprecated, or abandoned APIs that are still running and accessible. These forgotten endpoints can contain unpatched vulnerabilities.
• Internal vs. external APIs: Differentiating between APIs used only within the organization versus those exposed to external partners and the public.

• Improved security: By identifying all APIs, organizations can spot hidden vulnerabilities and enforce consistent security policies, protecting against unauthorized access, data leaks, and other cyber threats.
• Risk mitigation: Discovering shadow and zombie APIs allows security teams to take inventory of their true attack surface and address risks before they can be exploited.
• Enhanced compliance: Many data privacy regulations require an inventory of all systems that handle sensitive data. API discovery provides the visibility needed to meet these audit and compliance requirements.

• Accelerated development: Developers can find and reuse existing APIs instead of building redundant functionality from scratch. This improves efficiency and time-to-market.
• Better governance: An accurate, centralized API catalog allows organizations to enforce clear governance policies, track API usage, and manage the entire API lifecycle, from creation to retirement.

Managed APIs are those that are formally documented, actively monitored, and governed through standardized processes. They typically reside in API gateways or directories and follow defined lifecycle practices, from design and development to versioning, deprecation, and retirement. These APIs undergo security assessments, include authentication and authorization mechanisms, and are subject to usage monitoring and rate limiting.

Effective discovery of managed APIs focuses on catalog accuracy and integration with enterprise governance tools. Visibility into these APIs allows organizations to track performance, enforce compliance, and align usage with business goals. Discovery platforms can enhance management by linking APIs to metadata such as owners, SLAs, and usage statistics, enabling proactive maintenance and policy enforcement.

Shadow APIs are undocumented or unofficial APIs that operate outside standard processes, often spun up by development teams to support specific projects or features. These APIs may not undergo rigorous security checks or lifecycle management, making them an attractive target for attackers. Discovering shadow APIs is challenging, as they are not typically registered in official inventories or documentation, but is critical to maintaining control over the organization’s API surface area.

Shadow APIs can lead to unpredictable integration issues, inconsistent data flows, and regulatory violations, especially if they handle sensitive information. Discovery processes—such as scanning network traffic and analyzing logs—can reveal such hidden endpoints. By bringing shadow APIs under centralized governance, organizations reduce their security and compliance risks, avoid operational blind spots, and enforce best practices across the software development lifecycle.

Zombie APIs are obsolete or deprecated APIs that remain accessible despite no longer serving an intended purpose. These often result from previous versions of an application or left-behind integrations following system migrations and upgrades. Because they are forgotten or ignored, zombie APIs can expose vulnerabilities, act as backdoors to sensitive systems, and create opportunities for attackers to exploit outdated logic or weak authentication.

Discovering and decommissioning zombie APIs is essential for maintaining an accurate and secure API inventory. Leaving such endpoints unattended increases technical debt and reduces overall infrastructure hygiene. Managed discovery processes identify zombie APIs based on usage analytics, code inspections, and monitoring tools, enabling organizations to safely retire or isolate them before they can be leveraged in attacks.

Internal APIs are for use within an organization and are not exposed to external developers or partners. These APIs facilitate communication among internal applications and services, enabling developers to build, scale, and update systems in a modular fashion. Discovering internal APIs helps organizations identify integration points, ensure appropriate access controls are in place, and keep development teams informed about the tools and resources available within the company’s technology ecosystem.

Missing or outdated records of internal APIs can lead to redundant development efforts or increased technical debt. By systematically cataloging all internal APIs, teams can optimize system architecture, streamline maintenance, and align software initiatives with business needs. Additionally, visibility into internal APIs is the first step in applying consistent monitoring, versioning, and deprecation policies, all of which are essential for secure and reliable enterprise API management.

External or third-party APIs are delivered by external vendors, partners, or service providers. Organizations use these APIs to integrate outside functionality—such as payment processing, social media interactions, or cloud services—into their applications. Discovery of third-party APIs is essential for understanding the external data flows and dependencies within an enterprise architecture. It also enables organizations to administer access controls, monitor service level agreements (SLAs), and ensure contractual compliance.

Failure to monitor third-party APIs can introduce significant security and privacy risks, especially when these interfaces touch sensitive data or drive business-critical workflows. A discovery process identifies all third-party integrations, assesses their trustworthiness, and promotes proactive vulnerability management. In addition, it allows IT teams to respond quickly to changes in vendor offerings, deprecated endpoints, or emerging security concerns in external services.

Manual API discovery involves reviewing documentation, code, and infrastructure records to find and catalog APIs. This process may work for small organizations but quickly becomes impractical at scale. Manual methods are prone to errors and oversights, especially as modern development introduces APIs at a rapid pace, often as part of CI/CD pipelines or cloud-native deployments. As a result, critical endpoints can be missed, and the inventory rapidly becomes outdated.

Automated API discovery leverages network analysis, code scanning, log aggregation, and machine learning techniques to automatically identify and map APIs in real-time. These tools continuously monitor environments for new or changed interfaces, correlating multiple data sources to maintain a dynamic and up-to-date API inventory. They can uncover hidden or shadow APIs, alert teams to anomalies, and provide contextual insights for risk assessment, enabling more effective security and compliance enforcement.

The first step in API discovery is scanning network traffic and analyzing logs across all environments. Tools that monitor incoming and outgoing HTTP/S requests can detect API calls, endpoint patterns, and the protocols in use. Log analysis complements this by highlighting APIs accessed by applications, services, or users over time. This approach enables organizations to uncover undocumented or rarely used APIs that may not appear in official records.

Consistently monitoring real-time traffic and logs helps maintain a current view of the full API surface. Temporary or experimental APIs, which can pose security risks if overlooked, are more easily detected. Additionally, aggregating data from multiple monitoring sources can reveal usage anomalies or unexpected data flows, triggering further investigation and potential remediation.

Code repositories are a rich source of information for API discovery, especially in organizations practicing DevOps or microservices architectures. Reviewing source code, configuration files, and infrastructure-as-code scripts can reveal hardcoded endpoints, environment-specific configurations, and undocumented service integrations. Automated code scanning tools are often used to scour large codebases for characteristic API patterns, such as base URLs, authentication routines, or standard HTTP methods.

By inspecting both active and legacy code repositories, organizations can uncover APIs that are in development, unmaintained, or potentially orphaned. This source-level visibility complements network and log analysis, ensuring a more comprehensive understanding of API usage and exposure. Integrating code inspection into the API discovery process helps prevent accidental shadow API deployment, supports efficient refactoring, and highlights areas requiring stricter governance.

Once data is collected from traffic scans, log analysis, and code inspection, the next step is correlating these findings to build a centralized and validated inventory. This involves mapping observed endpoints to known services, identifying overlaps, and resolving discrepancies. Correlation enables teams to distinguish between duplicate, redundant, or obsolete APIs, producing a consistent view that informs operational and security policies.

An up-to-date, unified inventory facilitates exhaustive risk assessments, access control, and asset management. Knowing which APIs belong to which systems, their business owners, and their integration patterns enables targeted responses to vulnerabilities or incidents. Maintaining this inventory as a living document—automatically updated via continuous monitoring—keeps all stakeholders informed and supports ongoing modernization initiatives.

API environments are highly dynamic, with frequent changes as organizations deploy new applications or update existing ones. Ongoing monitoring is essential to ensure that the API inventory remains accurate and up-to-date. This requires continuous scanning of network flows, logs, and code repositories to detect new endpoints or unexpected changes. Automated alerts and dashboards can highlight anomalies or risks as soon as they appear, reducing the window of exposure.

Effective ongoing monitoring not only sustains compliance but also enables proactive risk management. By detecting rogue or unauthorized APIs in real time, teams can quickly isolate or remediate issues before they escalate. This continuous feedback loop strengthens governance, supports agile development workflows, and makes it possible to scale API security practices across complex enterprise environments.

API Discovery and Security Platforms

API discovery and security platforms provide automated tools for mapping, cataloging, and securing APIs across an organization’s entire infrastructure. These solutions use passive and active monitoring to detect both documented and undocumented APIs. They offer central dashboards, detailed analytics, and real-time alerts, enabling security teams to visualize the organization’s attack surface and respond to new threats as APIs evolve.

In addition to discovery, such platforms often integrate with broader security information and event management (SIEM) tools, facilitating compliance, vulnerability remediation, and incident response. They help organizations enforce access controls and validate security posture continuously. This integrated approach ensures that even as APIs proliferate across multicloud, hybrid, and containerized environments, the attack surface remains visible and manageable.

API Marketplaces and Directories

API marketplaces and directories are public or private hubs where APIs are registered, listed, and made available for discovery by internal or external developers. These platforms facilitate the publication and management of APIs, allowing teams to share endpoints, documentation, and usage policies within controlled environments. They streamline integration workflows by providing search, subscription, and analytics features for consumers.

For organizations, adopting internal API directories helps enforce governance by ensuring all APIs—whether internal or external—are cataloged, documented, and on-boarded centrally. This improves transparency, eliminates duplication, and fosters reusability, making it easier for teams to find and leverage existing APIs rather than rebuilding similar functions. Directories also support lifecycle management, versioning, and visibility into consumption patterns.

API Specification, Design, and Documentation Tools

API specification, design, and documentation tools automate the creation and maintenance of API schemas, documentation, and test harnesses. These solutions allow developers to define endpoints, methods, and data structures in standardized formats. These tools validate adherence to design guidelines, check for missing parameters, and generate interactive reference documentation, making API consumption more reliable.

Integrating specification and documentation tools into the development lifecycle not only accelerates discovery and onboarding, but also helps synchronize teams around a single source of truth. Machine-readable specifications make it easier to verify implementations, automate testing, and support continuous integration workflows. Well-documented APIs are also more easily discovered by internal and external consumers, reducing the likelihood of rogue or duplicated endpoints.

1. Maintain a Centralized, Continuously Updated API Inventory

A centralized API inventory serves as the authoritative system of record for all APIs used within an organization. Keeping this inventory continuously updated ensures visibility over all integration points, enables efficient governance, and lays the foundation for compliance with regulatory requirements. Automated tools should be leveraged to synchronize the inventory with real-time changes across network traffic, code repositories, and cloud environments.

Regular audits to reconcile the inventory with observable data—such as usage analytics, monitoring logs, and code scans—reduce the risk of overlooked endpoints. This transparency not only supports effective security management but also streamlines application modernization, migration, and retiring of legacy systems. Up-to-date inventories also aid in post-incident investigations and vulnerability assessments.

2. Integrate Discovery Into CI/CD Pipelines

Integrating API discovery into continuous integration and continuous deployment (CI/CD) pipelines ensures APIs are cataloged and reviewed as soon as they are created or updated. Automation at this stage catches shadow APIs, configuration errors, and compliance issues before they reach production. Code scanning, artifact inspection, and automated inventory synchronization should be part of build and release workflows to maintain consistency.

Making API discovery a standard component of CI/CD processes enforces best practices across all development teams, regardless of project scope or velocity. Feedback from the discovery process can trigger security checks, enforce policies, or prompt remediation of risky APIs before broader deployment. This reduces the technical debt associated with undocumented or unapproved endpoints and improves overall software delivery quality.

3. Monitor Hosts and Subdomains to Prevent Rogue Endpoints

Continuous monitoring of hosts, subdomains, and DNS records is essential for identifying unauthorized or misconfigured API endpoints. Rogue or forgotten endpoints often appear as subdomains or on infrastructure spun up for short-term projects, and they pose significant security risks if left unmanaged. Tools that scan DNS records, SSL certificates, and exposed services help detect and catalog such resources.

Routine monitoring enables rapid response to new or suspicious endpoints, reducing the time attackers may have to exploit vulnerabilities. Integrating this monitoring into both the discovery process and ongoing operational oversight helps close gaps in visibility. This is especially important in large, distributed, or cloud-centric organizations where assets are frequently provisioned and retired.

4. Map APIs to Business Functions

Mapping APIs to specific business functions ensures each endpoint is well understood, properly owned, and appropriately governed. This business-to-technology linkage clarifies which APIs are mission-critical, who is responsible for their maintenance, and what the operational impact would be if they changed or failed. Effective mapping enables better prioritization of risk management, audit, and incident response resources.

Organizations should maintain metadata about each API, documenting its purpose, related applications, data sensitivity, and business stakeholders. This approach improves planning for API versioning, migration, and deprecation. It also facilitates cross-team collaboration by making it easier for stakeholders to discover and evaluate APIs in the context of their business processes.

5. Foster Developer Awareness and Provide Tooling

Developer awareness is critical to preventing the proliferation of shadow and zombie APIs. Training developers on the risks of undocumented endpoints, secure API design principles, and the organization’s discovery tools extends governance to the earliest stages of the software lifecycle. Awareness enables teams to avoid security pitfalls and adhere to policies when creating, exposing, or consuming APIs.

Providing intuitive discovery, design, and documentation tools further empowers developers to register APIs, keep inventories updated, and align with security and compliance requirements. Self-service portals, integrated code scanners, and one-click publishing features improve the developer experience and reduce friction. Supporting a culture of shared responsibility for API visibility not only streamlines discovery, but also ensures that security is embedded in every phase of the development process.

Cloud Application Protection Service

Radware’s Cloud Application Protection Service provides an integrated framework for API discovery, protection, and governance. It automatically identifies active and shadow APIs across environments, classifies them by exposure and sensitivity, and applies tailored security policies to each. Using AI-driven behavioral analytics, it detects anomalies such as unauthorized calls, schema deviations, and data-leak patterns in API traffic. The service consolidates multiple modules—WAF, API protection, bot management, and DDoS mitigation—under a single platform, giving security teams unified visibility into both known and unmanaged APIs while maintaining business continuity across web and mobile applications.

Cloud WAF Service

The Cloud WAF Service enhances API discovery through continuous inspection of web and API traffic. It validates requests against API specifications such as OpenAPI or Swagger, detects unknown endpoints, and automatically adjusts protection rules as new APIs appear. The service protects APIs against injection, parameter tampering, and access-control abuse by enforcing context-aware policies and positive security models. Its adaptive learning engine minimizes false positives while maintaining compliance and visibility, enabling organizations to secure dynamic, microservices-based applications without slowing down development pipelines.

Bot Manager

Radware Bot Manager supports API discovery by revealing automated interactions with undocumented or shadow APIs that often evade traditional monitoring. Through advanced behavioral analysis, device fingerprinting, and intent classification, it distinguishes legitimate API clients from malicious automation targeting business logic or sensitive data. The solution blocks credential-stuffing, scraping, and enumeration attempts at the API layer while maintaining frictionless user experiences. Its analytics dashboards also help organizations visualize API consumption patterns, highlighting where exposure or abuse is most likely to occur—an important by-product of continuous API visibility and governance.

Cloud Network Analytics & Threat Intelligence

Radware’s Cloud Network Analytics and Threat Intelligence Subscriptions extend API discovery by providing a macro-level view of API traffic flows and potential attack sources across hybrid environments. By correlating telemetry from Radware’s global mitigation network with customer traffic, these tools identify abnormal API usage spikes or attempted exploit campaigns in real time. Enriched with threat-intelligence feeds from Radware’s ERT Active Attackers database, the analytics layer helps organizations map exposure, prioritize risk, and enhance API protection strategies based on current attack patterns and observed behavior in the wider threat landscape.