The Definitive API Security Testing Checklist [XLS download]

What would happen if a malicious actor managed to access your API without authorization and compromise sensitive user data? The repercussions can be horrendous. You could incur significant financial losses or even worse harm your reputation.

There is also a higher risk of security, just last year a 37% increase in API security incidents were reported.  which means that developers of API-based goods and services need to pay extra attention to this.

This initiative starts with a holistic understanding of API security testing, followed up with robust processes backed by a comprehensive API security testing checklist and guidelines.

What is API Security Testing? 

API security testing is a process that validates all aspects of securing APIs. At a high level, this ensures that the APIs are guarded against misuse and information leaks. Under the hood, API security testing entails a technical evaluation of each API, its request and response messages, query parameters, and any data exchanged between the API client/consumer and API gateway/producer to establish robust security measures and fortify the API against cyber threats.

The Benefits of API Security Testing

API security testing assumes the same level of importance as software security testing. Like software security testing, which aims to check for vulnerabilities in the software that may result in data breaches and system blackouts, API security testing ensures the same level of security guarantees. In modern software architecture, APIs are integral to any software deployed on the cloud. This approach is also known as API-first, wherein a product is developed based on a set of APIs that provide the core foundational services for software. Therefore, security testing of APIs that are part of the software, in turn, helps to establish a stronger security posture management for the overall software application.

Additionally, API security testing offers several benefits to the people and organizations involved in API development and management.

• If you are a developer building API-driven products and services, API security testing is a must. It ensures early detection of vulnerabilities during the development phase to enforce proper checks and balances to safeguard APIs from cyber threats.
• API security testing is mandatory for software vendors that leverage APIs within their products and services. It helps them set reasonable security guarantees with their customers, reduce reputation damage risks, and get certified on security-related compliances.
• For customers, API security should be one of the primary evaluation criteria for choosing APIs and API-based products and services. This practice enables them to ensure that the APIs are in harmony with the organization’s overarching security policies, helping maintain a consistent security posture for all business functions.

How To Perform API Security Testing?

With the OpenAPI specification bringing much-needed standardization and the widespread embrace of RESTful and GraphQL-based architectures, APIs follow a consistent, machine-interpretable format and communication pattern. This is good news for developers and security testers since it allows them to establish a thorough API security testing checklist, covering every nook and cranny, like checking each bolt in a high-security safe.

Assuming the API spec is in place,  here is a 21-point API security testing checklist based on the seven broader areas around the functioning of APIs:

1. Authentication and Authorization Checks

First comes the API access related checklist. Every API is designed to allow access to specific authenticated identities. Additionally, these identities must have specific roles they can perform.  Based on this requirement, the API authentication and authorization checklist should check for the following:

• [  ] The API must use a strong authentication mechanism, such as OAuth 2.0 or JWT (JSON Web Token).
• [  ]—The API must have an authorization check to ensure only privileged identities can invoke specific API endpoint/HTTP methods.
• [  ] – The API should consider implementing multi-factor authentication for more robust security.

2. Input Validation and Output Encoding

These checks ensure the sanctity of data exchange between the API consumer and producer.

• [  ]—The API must validate each input field according to the format defined in its spec to ensure proper validation of numerical, string, mixed inputs, and special fields (for example, email address and regular expressions).
• [  ] – The API must scan for special characters, escape sequences, or hidden characters in the request parameters to detect malicious code injection and reject such requests.
• [  ] – The API must adhere to the output encoding as per the content type defined in the spec.

3. Rate Limiting and Throttling

These checks ensure fair access to the APIs and prevent malicious actors from hijacking the API gateways and backend systems that host the APIs.

• [  ]—The API must be deployed with specific throttling policies to control the number of requests it can receive within a granular timeframe.
• [  ]—The API must be deployed within specific rate limit tiers to cap the total number of requests it can receive over a time period.
• [  ]—The API must implement dynamic throttling policies and monitor abnormal requests, such as repeated invalid authentication, to prevent potential brute force and DDoS attacks.

4. Error Handling and Logging

These checks ensure that errors related to invalid or non-successful API responses are appropriately handled and logged without leaking data.

• [  ]—The API must generate access and error logs for all requests and responses, emphasizing additional information logs for non-successful HTTP response codes.
• [  ] – The API must ensure the log messages do not reveal anything about the data or data schema used at the API backend.
• [  ]—The API should implement additional logging integrations to send real-time alerts and facilitate the immediate assessment of possible security incidents.

5. Data Encryption and Transport Layer Security

These checks ensure that all the data exchanged between the API provider and consumer applications are secured end-to-end.

• [  ] – The API must implement TLS (Transport Layer Security) to encrypt request and response payload.
• [  ] – The API must implement secure storage vaults to safeguard the private keys and tokens used in encrypted data exchange.
• [  ]—The API must implement rotation policies to minimize the risks of data breaches from using the same encryption keys for an extended period.

6. Testing for Business Logic Vulnerabilities

These checks ensure that the backend business logic triggered by the API request does not introduce any security loopholes.

• [  ]—The API must implement additional security checks to prevent unauthorized data modification through HTTP POST, PUT, and DELETE methods.
• [  ] – The API business logic must be guarded against leaking internal data structures, database tables, or sensitive data in response to SQL injections through malicious code hidden in API request parameters.
• [  ]—The API business logic must implement additional guardrails to prevent possible back-channel security loopholes caused by features such as bulk data upload or third-party integrations.

7. API Documentation and Version Control

Although these checks do not directly impact API security, they are essential to establishing a consistent set of API test criteria for validating all APIs within an API suite.

• [  ] – The API must have a well-defined specification documented according to the OpenAPI standard specification.
• [  ] –  All APIs that are part of the active inventory or catalog of the API suite must be periodically evaluated to eradicate deprecated, zombie, or shadow APIs that are unused or temporarily created.
• [  ]—All APIs must be versioned so that different versions of the same API can be distinctly tested for security testing coverage and to manage security-related patches and fixes across all versions.

Best Practices for Ongoing API Security Monitoring

Security is a moving target. Therefore, no API security testing checklist can address the ever-evolving vulnerabilities and hacking tactics. Moreover, APIs deployed in real-world environments undergo modifications through ongoing code maintenance, which may introduce unknown security loopholes even without changes in API specs and design.

Considering these risks, it is vital to treat API security testing as a holistic API hardening practice that combines the API security testing checklist with an overarching and continuous API security monitoring process that ensures:

1. All bug fixes done on the API business logic are scanned and reviewed for code-level vulnerabilities.
2. API business logic is continuously analyzed for software composition analysis to detect third-party software components and libraries with previously known vulnerabilities.
3. All API code modifications undergo security compliance testing and continuous security monitoring as part of automated CI/CD pipelines. 

Take Charge of Your API Security Testing 

Today where everything is linked, APIs are what keep the digital apps running. There are, however, more security risks that come with this increased dependence. A strong API security testing approach is needed to make sure that your APIs are secure and private.

With platforms like Spectral, you are in-charge of the protection of your API. By adding Spectral to your CI/CD pipeline, you can follow DevSecOps principles and proactively discover and mitigate vulnerabilities early in the development process. Our cutting-edge platform constantly provides real-time continuous monitoring and assessment, making sure that your APIs are safe in the long term.
Ready to elevate your API security?Start your free trial of Spectral today and experience the power of proactive API protection