Reduce Critical Vulnerabilities by 95% with Application Context

Shadow APIs: Finding APIs You Didn’t Know Were There

Applications and services rely on APIs to communicate with other applications and services. To facilitate these communications, API usage has grown rapidly over the past few years. In 2021, the global API management market was $2.8B, and it is expected to reach $41.5B by 2030.

API growth also means attack surface expansion. APIs can be used to gain access to sensitive data and systems. In this blog, we’ll explain what shadow APIs are, explore different tools and methods for detection, and discuss best practices to minimize risk related to shadow APIs.

But First, What is a Shadow API?

Shadow APIs are APIs that are used by employees or teams without the knowledge or approval of the organization’s IT department. These APIs are often created to fill a specific need or to work around the limitations of existing systems. 

Other Unmanaged APIs

In addition to shadow APIs, there are rogue APIs and zombie APIs. 

Rogue APIs are APIs that are intentionally created and used to circumvent security protocols or gain unauthorized access to data or systems. Zombie APIs are APIs that are no longer in use but are still active and accessible, making them a potential entry point for cyberattacks. 

Shadow, rogue, and zombie APIs can be difficult to detect and secure, making them an attractive target for cybercriminals. Here are some strategies that organizations  can use to identify, monitor, and secure all APIs, 

How to Detect Shadow APIs

Detecting the presence of shadow APIs is a significant challenge for organizations, as they are usually not documented or approved. However, there are ways to reduce the risk associated with shadow APIs.

API Proxies

API proxies are intermediary servers that act as a gateway between client applications and backend services. They are designed to provide an additional layer of security and management for APIs, allowing businesses to monitor and control API traffic more effectively. Proxies can be configured to perform various tasks, such as caching, authentication, rate limiting, and traffic routing.

API proxy process

API proxies can also help detect shadow APIs by intercepting all API requests and responses, providing visibility into all API traffic flowing through the organization. By using API proxies, businesses can set up policies to control access to APIs, including unauthorized APIs, and block any traffic that does not conform to these policies. 

Additionally, API proxies can detect and report any suspicious API activity, such as unexpected API calls, traffic spikes, or requests from unregistered client applications. This capability can enable businesses to identify shadow APIs and any other unauthorized API usage, thereby allowing them to take prompt action to mitigate the risks associated with such activities. 

Log Analyzers

Log analyzers are tools that enable businesses to analyze and monitor log files generated by various systems and applications, including APIs. These tools allow organizations to collect, parse, and analyze large amounts of log data, providing visibility into system and application behavior.

Log analysis process

Log analyzers can help detect shadow APIs by identifying unusual patterns of API activity in log data. By analyzing API logs, businesses can identify any unauthorized API usage, such as requests from unapproved client applications or calls to unregistered APIs. 

Log analyzers can also be used to detect any suspicious API activity, such as high volumes of traffic, unusual API calls, or repeated failed login attempts. Additionally, log analyzers can be integrated with other security tools, such as intrusion detection systems and security information and event management (SIEM) solutions, to provide a comprehensive view of API activity and security incidents.

Application Monitoring

Application monitoring tools enable businesses to track and analyze the performance and behavior of their applications and provide detailed insights into how applications are functioning, including how they interact with APIs.

Application monitoring tools can help detect shadow APIs by providing visibility into all API traffic flowing through the organization’s applications. These tools can track API usage, including unauthorized API calls, and alert administrators to any suspicious activity. They can be configured to perform real-time API monitoring, automatically flagging any unauthorized or suspicious API activity for review.

Application Security Testing Tools

Application security testing (AST) tools identify security vulnerabilities in applications, including APIs using a variety of techniques, such as static and dynamic code analysis, fuzz testing, and penetration testing, to identify weaknesses and potential attack vectors.

static testing

Application security testing tools can help detect shadow APIs by analyzing the code and behavior of applications to identify any unauthorized API calls or activity. These tools can scan the code and configuration of applications to identify any references to unauthorized APIs, as well as detect any unexpected or suspicious API calls during runtime. Additionally, security testing tools can perform automated API testing to identify any vulnerabilities or weaknesses in the API itself.

API Security Tools

API security tools detect and mitigate the risks associated with APIs. These tools provide a range of features, such as authentication and access control, data encryption, and threat detection, to ensure the security and integrity of APIs.

api tutorial

API security tools can help detect shadow APIs by monitoring all API activity and enforcing strict security policies. These tools can authenticate and authorize all API requests, ensuring that only authorized clients can access the API. Additionally, API security tools can encrypt data in transit and at rest, providing end-to-end security for all API communications.

Best Practices for Avoiding Shadow API Creep

Avoiding shadow API creep requires a proactive approach to managing APIs, including comprehensive documentation, inventory tracking, and security audits. 

API Documentation

API documentation is a critical component of managing APIs and avoiding shadow API creep. It is important to ensure that all APIs are documented, including details such as the API endpoint, authentication requirements, and usage policies. 

Automating this process can reduce manual effort, increase accuracy, and ensure that documentation is always up-to-date.

One way to automate the API documentation process is by using open-source tools, such as Swagger or OpenAPI, which allow businesses to generate documentation automatically based on the API code.

These tools can extract information from the API code, such as endpoint URLs, parameters, and responses, and generate comprehensive documentation in a standardized format. This can save time and reduce the risk of errors that can occur when manually creating documentation.

API Inventory

API inventory tracking is essential for avoiding shadow API creep. Organizations should maintain a comprehensive inventory of all APIs, including third-party APIs, and regularly review and update this inventory. 

api discovery and inventory

Automating the API inventory process can also provide significant benefits. Businesses can use API management solutions, such as Apigee or AWS API Gateway, to track and manage their APIs automatically. 

These solutions can maintain a comprehensive inventory of all APIs, including details such as the API endpoint, usage policies, and security requirements. 

This can enable businesses to identify any unauthorized or unapproved APIs, as well as ensure that all APIs are properly documented and secured.

API Security Audits

API security audits are critical for identifying and mitigating any security risks associated with APIs. 

Regular security audits can help businesses identify any vulnerabilities or weaknesses in their API infrastructure, as well as identify any unauthorized or suspicious API activity. 

Automating API security audits can increase the efficiency and accuracy of the audit process, as well as identify and mitigate security risks more quickly.

One way to automate API security audits is by using open-source tools, such as OWASP ZAP. These tools can perform automated security scans of APIs, identifying potential vulnerabilities or weaknesses in the API infrastructure. They can also generate detailed reports of any issues found, including recommended remediation steps.

Another approach is to use API security monitoring solutions, which look at API traffic in real-time, analyzing the traffic for any suspicious or unauthorized activity. They can also perform automated threat detection and mitigation, blocking any malicious or suspicious traffic automatically and providing detailed reports of any incidents.

How Bionic Detects Shadow APIs

Bionic helps teams detect and manage shadow APIs.

API Discovery and Mapping

First, Bionic discovers and maps all application services and APIs within an application, including shadow, rogue, and zombie APIs. Bionic’s unique approach doesn’t rely on actual API calls or traffic, so you’ll get a full picture of how each API connects to each microservice, regardless of whether it’s being used. 

API Inventory

From the basic discovery and mapping, Bionic generates a complete inventory of the application. This inventory includes every service, data source, dependency, and API. In Bionic’s API and Interface inventory table, you’ll be able to see the source, destination, technology type, whether it’s upstream or downstream, the interface, port type, and port — all the core components of API documentation.

API Inventory

These first two capabilities – API discovery and mapping and API inventory – are incredibly powerful for detecting anomalous APIs. Having an accurate understanding of what’s in your application, as it is in production, is incredibly difficult. Keeping those maps and inventories current is further complicated when changes are pushed to production frequently. 

API Security

Bionic can continuously monitor APIs to understand how each change affects the application’s overall security and risk. For example, if an update contains a new service in an application and that service is internet-facing but isn’t using API authentication, Bionic will flag that as a security violation. Bionic also takes into account sensitive data that could be accessible to that unauthenticated API to create an overall risk score for the service.

API security


APIs need to be discovered, mapped, inventoried, and secured. Bionic makes it infinitely easier to see and secure all APIs, including shadow, rogue, or zombie APIs, that you might have in your applications. 

Interested in learning more about how API security fits into ASPM? Check out our ebook on ASPM.

Did you find this blog helpful or interesting?

Click the social media button of your choice to share the blog with you friends and colleagues.

See a Live Demo of the Bionic Platform