Introduction: The need for simplified API discovery

APIs have become the foundation of modern applications, powering everything from customer-facing mobile apps to internal business services. With this rapid growth, organizations face an expanding and increasingly opaque attack surface. Many APIs are undocumented, hidden within single-page applications, or integrated through third-party services, making them difficult to track and secure.

Typical API discovery methods often rely on deploying network sensors or software agents. While useful in specific contexts for deeper insights, such approaches can introduce complexity and performance overhead. To operate at scale, security teams also need a faster, simpler way to uncover the APIs in use across all their environments without slowing down operations.

This is where sensorless, or agentless, API discovery comes in. By capturing and analyzing traffic generated during API security scans, agentless methods can automatically infer API endpoints and operations without the need to deploy agents or run manual discovery.

Key takeaways

• Sensorless (aka agentless) API discovery eliminates the need for deployment-heavy traffic analysis agents.
• It provides centralized visibility, broader coverage, faster adoption, and reduced complexity.
• Agent-based discovery methods remain useful but can create blind spots and inefficiencies if used as the only method.
• API security on the Invicti Platform includes multi-layered API discovery that combines sensorless and optional agent-based discovery with scanning, validation, prioritization, and compliance alignment.

What is sensorless (agentless) API discovery?

Sensorless API discovery is a method of identifying APIs by analyzing live application traffic during automated scans. Instead of deploying monitoring agents or relying solely on pre-existing specifications, the scanning engine generates real user-like traffic, observes which calls are made to APIs, and reconstructs the API specification directly from that activity.

This approach differs from traditional agent-based discovery, which requires installing components across environments to monitor traffic flows. With agentless discovery, there is no deployment footprint, no extra software to maintain, and no dependency on internal network access.

Organizations are increasingly looking to agentless methods because they enable faster adoption, reduce operational burden, and deliver a more accurate picture of the APIs actively powering their applications.

API security on the Invicti Platform includes multi-layered discovery, offering both sensorless and agent-based network traffic analysis (NTA) discovery. This gives users the flexibility to deploy NTA where more detailed insights are needed while maintaining the broad coverage and convenience of sensorless discovery.

Limitations of agent-based API discovery

Agent-based API discovery has long been used as the primary means to gain visibility into API usage, but relying entirely on this method comes with significant trade-offs:

• Deployment overhead and scalability issues: Rolling out agents across a large enterprise environment requires time, approvals, and ongoing updates.
• Blind spots in hybrid/cloud environments: Agents may miss traffic in distributed and containerized architectures where APIs are dynamically created.
• Maintenance and performance impacts: Continuous agent monitoring can add performance load and create operational friction, especially in sensitive production systems.

This is why Invicti provides an agent-based discovery feature as a complement to other approaches, but does not require its use for effective API discovery.

Benefits of sensorless API discovery

The ability to perform sensorless API discovery unlocks a number of benefits related to API security:

Centralized visibility across environments

Agentless discovery delivers a unified view of APIs across on-premises, cloud, and hybrid environments. This ensures that hidden or undocumented endpoints powering applications are also surfaced in a single inventory.

Faster adoption and lower operational overhead

With no agent deployment requirements, teams can begin discovering APIs immediately, as soon as they can run a DAST scan. This accelerates time-to-value and eliminates the administrative burden of managing agents.

Continuous monitoring without deployment burden

By integrating discovery into security scans that need to be run anyway, sensorless discovery can continuously update API inventories as applications evolve and are incrementally tested. This provides continuous coverage through scheduled and pipeline-integrated scans without requiring infrastructure changes.

Better alignment with DevSecOps pipelines

Agentless discovery fits naturally into CI/CD workflows where automated security scans are already running. This alignment ensures APIs are identified and secured early in development without adding extra steps.

How Invicti’s DAST-first AppSec platform enables agentless API discovery

Finding a way to identify APIs without constantly monitoring and analyzing all your application traffic has only become possible recently thanks to advances in automated dynamic application security testing (DAST). Invicti is pioneering this approach by using its DAST scanner to actively generate representative application traffic during crawling and scanning, thus providing a good approximation of typical API calls made in production.

Automated inventory and visibility on the Invicti Platform

While DAST on the Invicti Platform is running scans that automatically crawl and probe applications, it can also capture API calls made during those interactions, analyze them to reconstruct the endpoints and specs, and store results in an API inventory. This provides accurate, real-time visibility across the API attack surface.

Continuous validation of vulnerabilities

Agentless discovery on its own identifies APIs, but taking a DAST-first approach means you can also scan those APIs for vulnerabilities. With Invicti’s proof-based scanning, exploitable vulnerabilities in APIs can be automatically validated in the same way as for application frontends. For confirmed issues, the risk of false positives is near zero (0.02%, to be exact), which lets you focus on actionable vulnerabilities.

Risk prioritization with no agents required

With integrated risk scoring, the Invicti Platform helps security teams prioritize the APIs and vulnerabilities that pose the greatest risk. All of this works across all your environments without the need to deploy agents or add operational complexity (although you can deploy the additional network traffic analysis agent where more depth is needed).

Compliance-ready reporting

In the same ways that DAST is tech-agnostic, sensorless API discovery can be performed regardless of the internal specifics of your environments. This API visibility supports regulatory requirements for inventory management and risk documentation. Invicti additionally provides compliance-ready reports that demonstrate coverage across applications and APIs.

Best practices for implementing agentless API discovery

• Evaluate environments where agentless is most impactful: Focus first on distributed, cloud-native, and hybrid applications where agents are hardest to manage.
• Integrate with CI/CD for proactive visibility: Include discovery scans in automated pipelines to catch APIs as they are deployed.
• Pair with vulnerability validation for accuracy: Ensure discovery results feed directly into testing workflows to confirm which APIs are exploitable.
• Educate teams on governance around APIs: Provide clear guidance for developers and security staff to manage discovered APIs responsibly.

Business impact of sensorless API discovery

Adopting sensorless API discovery can deliver tangible benefits for both security and business operations:

• Reduced cost and complexity of security programs: Eliminates agent deployment and maintenance overhead.
• Stronger compliance posture with full visibility: Supports regulatory frameworks that require accurate API inventories.
• Faster response to emerging API threats: Enables rapid detection and testing of APIs exposed through application changes.
• Greater executive confidence in security operations: Provides clear visibility and evidence-backed reports that build trust in AppSec programs.

From discovery to action: The time to go sensorless is now

Sensorless API discovery offers a modern, scalable way to uncover and secure APIs without the deployment challenges of traditional agent-based methods. By combining multi-layered discovery (including sensorless), scanning, validation, and risk prioritization in one platform, Invicti lets you broaden visibility across your API attack surface.

Get a demo of how Invicti enables sensorless API discovery for better visibility and risk reduction.

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