API security: A quick review
API security is the practice of safeguarding application programming interfaces from threats, vulnerabilities, and unauthorized access. APIs serve as critical communication gateways between users, applications, and servers, making them prime targets for cybercriminals. This expanded attack surface has led to a 10% year-over-year increase in attacks targeting business logic vulnerabilities, which now account for 27% of all API attacks.
Recent years have brought a surge in API-based attacks. These attacks are particularly damaging because APIs often carry sensitive data and expose business logic that helps attackers understand system vulnerabilities. Open source API security tools provide an effective defense against data theft, infrastructure compromise, and unauthorized access attempts.
Modern apps are powered by hundreds of APIs (estimates put it at an average of 613 APIs per enterprise) that facilitate communication and data transfer between users and apps, as well as between different microservices in an app. If not properly secured, that’s a potential 613 entry points for API attacks that could result in data theft, compliance violations, and financial and reputational damage.
So what does it mean to secure an API? API security includes measures such as:
API authentication and authorization, which control user access to and actions within APIs
Data encryption, which protects data transmitted by APIs using cryptographic hashes
Rate limiting, which caps the number of API requests to prevent DDOS attacks and API abuse
Input validation, which verifies user input to prevent injection and cross-site scripting attacks
Robust API security also involves implementing best practices and deploying API security tools to monitor and test APIs.
Choosing the right API security tool: 7 must-ask questions
Selecting the right open source API security tool requires evaluating capabilities that align with your specific security needs and development workflows. When choosing an OSS API security solution, verify that the tool offers these capabilities:
API discovery: Can the tool scan your enterprise’s entire cloud environments to discover and inventory all APIs and API endpoints?
Integration: Does it integrate into your development environment, CI/CD pipelines, and existing security solutions without disrupting your workflows?
Testing: Can it run dynamic application security testing (DAST) scans of your APIs to detect runtime bugs and security gaps that can be revealed only when clients and servers interact?
Runtime protection: Can it conduct comprehensive scans and provide actionable insights to help you address common API security vulnerabilities like broken authentication, misconfigured API endpoints, and others listed in the OWASP Top 10 API Security Risks?
Compliance: Can the API security tool facilitate compliance with regional and industry-specific regulatory standards such as GDPR, PCI DSS, and HIPAA?
Scalability: As your app and API needs grow, can the tool handle increasingly large and complex workloads without slowing down your DevSecOps processes?
Maintenance and support: Are security and performance updates released regularly to fix issues in the tool? Does the solution have an active community to offer you support should you need help utilizing it?
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Types of open source API security tools
Open source API security tools come in a few main categories. Here are some of the most common types you'll see:
API vulnerability scanners: These tools scan your APIs for known vulnerabilities, misconfigurations, and common security issues. Examples include ZAP and Akto.
Dynamic testing tools: These simulate real-world attacks and test your APIs in action. Tools like SoapUI fall into this group.
API specification and design linters: Tools like Spectral help you catch security issues early by analyzing API specs for misconfigurations and policy violations before deployment.
Functional and integration testing: Tools like Hurl, Rest Assured, and Kong Insomnia help you test API functionality and catch issues before they reach production. While not always security-focused, they're useful for validating expected behavior and catching edge cases.
API documentation and exploration: Swagger UI and similar tools let you interact with and test APIs through a visual interface, making it easier to spot unexpected responses or missing protections.
Given that research from 451 Research found enterprises have an average of 15,564 APIs in use, most teams use a mix of these tools to cover different parts of the API lifecycle. The right combination depends on your stack, your risk tolerance, and how much manual effort you want to invest.
OSS API security tools to consider
These nine open source API security tools offer distinct approaches to protecting your APIs, from comprehensive scanning to specialized testing capabilities.
1. APIsec|Scan
APIsec|Scan is an API security testing solution that conducts non-intrusive scans to discover common vulnerabilities in APIs.
Features
Integrates into multiple software development pipelines, including Git and Bitbucket
Supports manual and scheduled tests
Uncovers dependency and runtime vulnerabilities using different scanning techniques such as API software composition analysis, static application security testing, and dynamic application security testing
Pros
Enables automatic API discovery and scanning
Detects common vulnerabilities like suboptimal attribute-based access control (ABAC) and role-based access control (RBAC) configurations
2. Burp Suite
Burp Suite Community Edition is primarily a dynamic application security testing tool, but it has extended functionality to enable API endpoint protection.
Features
Has a crawler for discovering OpenAPI documents that automatically identify exposed API endpoints
Detects SQL injection, cross-site scripting (XSS), and CSRF attacks
Pros
Capabilities can be extended with various add-ons
Has a strong community of professionals providing support
3. Curity Identity Server (Community Edition)
Curity Identity Server Community Edition is a popular OAuth server for managing API security posture. It provides modern scanning capabilities to authenticate API endpoints, web apps, and mobile apps.
Features
Enables API access management
Supports various authentication mechanisms, including OpenID Connect, OAuth 2.0, and custom authentication
Supplies API tokens to minimize the risk of XSS and CSRF attacks
Pros
Provides single sign-on and customized claims to streamline user authentication and authorization
Offers logging and user management to track user and system actions
4. Hurl
Hurl is a command-line tool for testing HTTP API requests and validating responses. It allows you to conduct complex assertion tests to validate HTTP responses using headers, status codes, and response bodies.
Features
Uses a straightforward syntax written in plain text format
Works with REST, GraphQL, and SOAP APIs, ensuring comprehensive coverage of various HTML content
Pros
Supports GitHub Actions and Bitbucket, enabling easy integration into CI/CD pipelines for automated API testing
Is lightweight and easy to deploy, adding little to no performance overhead to your stack
5. Kong Insomnia
Kong Insomnia’s REST Client is a solution designed for building, testing, interacting with, and debugging various APIs.
Features
Supports multiple testing environments including Git, cloud, and local development environments
Supports several advanced scripting capabilities for testing, validating, and manipulating HTTP requests and responses to detect common API vulnerabilities
Pros
Is a lightweight tool with 350+ open-source plugins that can be added or removed as the need arises
Supports REST, GraphQL, gRPC, and SOAP APIs and analyzes HTTP and WebSocket requests, enabling comprehensive debugging and testing
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6. Rest Assured
Rest Assured is an API security testing solution designed for testing RESTful APIs written in Java. It’s a well-maintained project with an active community of developers and security engineers.
Features
Handles various authentication mechanisms, making it ideal for securing API endpoints
Supports JSON and XML formats for flexible data transfer during API testing
Handles multiple request types, such as POST, GET, DELETE, PUT, PATCH, etc., which it uses to verify API performance
Pros
Fluent API that simplifies API testing
Supplies cross-site request forgery (CSRF) tokens to minimize the risk of CSRF attacks on APIs
7. SoapUI
SOAP UI is an API testing solution designed to provide a spectrum of capabilities, including API load, functional, mocking, and security tests.
Features
Supports multiple API protocols such as REST, SOAP/WSDL, GraphQL, and JMS
Offers drag-and-drop features for designing custom test scenarios
Pros
Has a user-friendly GUI
Integrates easily with CI/CD pipelines to automate security testing across the SDLC
Has a vibrant open-source community of developers and security experts
8. Swagger UI
Swagger UI is a popular real-time API behavior testing solution. It provides a visual interface that empowers development teams to scan and interact with REST API resources without requiring access to implementation logic.
Features
Facilitates API authentication via authentication tokens and credentials
Enables real-time scans of API requests, including POST, GET, PUT, and DELETE
Pros
Has a dependency-free architecture that enables integration with various development environments
Enables complete access to Swagger UI’s source code to allow for seamless customization
9. ZAP
Zed Attack Proxy (ZAP) is a web application vulnerability scanner that uses fuzzing, active, and passive scanning techniques to conduct DAST-like API scans. Though it is primarily a DAST tool, it offers various add-ons for API scanning, including OpenAPI, SOAP, GraphQL, and import URLs add-ons.
Features
Handles various API authentication techniques such as basic auth, OAuth, and JWT
Has proxies for crawling APIs, intercepting API requests, and delivering malicious payloads to API endpoints
Pros
Conducts real-time scans
Supports scan-policy customization
Wiz + OSS API Security Tools = Unified API Security
Open-source API security tools give teams a strong foundation for validating specifications, enforcing standards, and catching issues early in development. They’re flexible, transparent, and built to slot naturally into developer workflows – which is exactly why so many teams rely on them as the first line of defense.
Wiz builds on that strength by extending API security beyond the pipeline and into the full cloud environment.
Wiz’s agentless approach automatically discovers APIs across cloud and containerized workloads, identifies exposed services, and maps how those APIs interact with identities, data, and network paths. And with Wiz’s dynamic scanner, teams can continuously test real API behavior in running environments — finding logic flaws, authentication gaps, and exposure patterns that static or spec-based tools can’t always surface.
Together, OSS tools handle developer-centric checks in code and CI/CD, while Wiz provides the runtime visibility, cloud context, and dynamic testing needed to understand how those APIs behave in the real world. It’s a complementary workflow: OSS ensures quality and consistency upfront; Wiz ties it all together with continuous discovery, risk prioritization, and runtime security.
If you want to see how Wiz amplifies your existing OSS API security stack without disrupting it, request a demo and explore the full, contextual view of your API landscape.
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