API security risks, testing, protection best practices

Adam Cheriki, Co-founder & CTO, Entro
January 18, 2024

As per the State of Developer Experience report released in 2023, 98% of developers perceive APIs as crucial in aiding their and their team’s productivity. APIs (Application Programming Interfaces) are important parts of many business systems. They make it easy to connect and work with different software programs.

However, the growing dependency on APIs has also heightened the potential for security lapses and the need to instill API key security best practices.

Here, we delve into the potential security risks associated with APIs, the significance of thorough API vulnerability detection, and API security best practices.

What is an API

An Application Programming Interface (API) is a set of guidelines and protocols designed to facilitate the development and interaction of software applications. APIs establish the methods and data formats that a program can employ to communicate with other software or services, functioning as a facilitator for diverse software systems to communicate and exchange data. This fosters a more straightforward development process.

Types of APIs

Here is a classification of APIs based on their accessibility and use-case requirements.

    1. Public APIs: They are made available to other developers for use over the internet and are accessible over the internet.

    1. Partner APIs: These are APIs shared with business partners. They are not publically accessible and generally require specific contractual agreements.

    1. Internal APIs: These are used within a company or organization to improve internal systems by sharing services between different parts of the organization.

    1. Composite APIs: These APIs combine multiple data or service calls into one API call. They can be public, partner, or internal APIs.

Types of API architecture

There are several different types of API architecture styles, each with its own unique characteristics and use cases:

    1. REST (Representational State Transfer): Stands out as one of the most prevalent API architectures.

    1. SOAP (Simple Object Access Protocol): The SOAP protocol exchanges structured data in web services.

    1. GraphQL: Takes a different approach from REST and SOAP by enabling clients to specify the data they require precisely.

    1. gRPC: Emerges as a high-performance, free platform with Protocol Buffers (protobuf) as its interface definition language.

    1. RPC: RPC is a secure and straightforward API for executing actions on remote servers, responding to client requests with JSON or XML and handling multiple parameters for internal processes.

Types of API security risks

Here are some of the API security risks you need to before securing APIs:

    1. Inadequate authentication and authorization: APIs that do not properly verify the identity and permissions of users pose a significant risk.

    1. Injection attacks: APIs are susceptible to various injection attacks, such as SQL injection, where malicious code is inserted into API requests to manipulate data and compromise systems.

    1. Unprotected API endpoints: If API endpoints are left unprotected or insufficiently protected, they become an easy target for attackers to exploit.

    1. Insecure data exposure: APIs often handle sensitive data, and if they do not properly secure this data during transmission or at rest, it can be intercepted or accessed by unauthorized individuals.

    1. Lack of encryption: Unencrypted data can be intercepted during transmission, making it critical to use protocols like SSL/TLS for data transmission.

    1. Insecure direct object references: APIs that reveal internal object references without appropriate authorization checks may enable attackers to manipulate parameters, potentially leading to unauthorized access to sensitive data.

    1. Denial of Service (DoS): APIs that are not adequately protected against DoS attacks can be overwhelmed with malicious requests, causing service disruptions or complete unavailability. Rate limiting and request validation can help mitigate this risk.

    1. Insecure deserialization: APIs that deserialize untrusted data without proper validation and integrity checks are vulnerable to attacks that can lead to remote code execution, privilege escalation, or unauthorized data access.

Importance of API security testing

Here are some key points highlighting the benefits of API security testing:

    1. Data protection: APIs manage sensitive data, and vulnerabilities can lead to breaches. Security testing holds significant importance in identifying and rectifying vulnerabilities, safeguarding user data, and preventing unauthorised access.

    1. Prevention of unauthorized access: APIs are frequent targets for unauthorized access. It’s important to have secrets management at every level of your system to ensure only trusted identities have access.

    1. Protection against injection attacks: API security testing is essential for identifying and mitigating vulnerabilities like SQL injection and XML injection, safeguarding data integrity and maintaining the trustworthiness of API-processed information.

    1. Thwarting DOS attacks: API security testing is crucial to identify and mitigate vulnerabilities that could be exploited in Denial of Service attacks, ensuring the availability and performance of APIs by preventing system overload from malicious flooding.

    1. Mitigating cyber attacks: APIs are attractive targets for cyber attacks such as SQL injection, cross-site scripting (XSS), and other common web vulnerabilities. Implementing security best practices, such as input validation and output encoding, helps mitigate these risks and ensures that APIs are not susceptible to common attacks.

How to secure REST API

Here are some guidelines to help you secure REST API:

    1. Use HTTPS: Always use HTTPS to encrypt the data transmitted between the client and the server to keep communication safe and prevent attacks like man-in-the-middle attacks.

    1. Input validation: Validate and sanitize all input to prevent common security vulnerabilities such as SQL injection, cross-site scripting (XSS), and other injection attacks.

    1. Rate limiting: Prevent abuse and protect against DOS attacks to ensure that a single user or application cannot overwhelm your API with too many requests.

    1. Logging and monitoring: To monitor API activities effectively, log pertinent information for debugging and auditing purposes. Regularly review these logs to detect any suspicious activities. An end-to-end secrets security solution like Entro is useful here as it gives you much-needed context on the risk level of an API attack.

    1. Error handling: Ensure effective error handling by implementing robust mechanisms while refraining from divulging sensitive information in error responses. Provide clients with generic error messages, reserving detailed error information for server-side logging.

    1. Regular security audits: Regularly conduct security audits and penetration testing to identify and rectify potential vulnerabilities. Maintain up-to-date dependencies to promptly address any known security issues.

    1. Governance policies: Establishing and enforcing API governance policies is a highly effective strategy for shadow API security. These policies should provide clear guidelines on API creation, specifying authorized creators, proper creation procedures, and appropriate usage protocols.

Best practices to protect APIs

Companies must protect APIs to secure sensitive data, maintain user privacy, and prevent unauthorized access. Here are five API key security best practices:

    1. Authentication and authorization – Setting up secure authentication measures is important to ensure clients who access the API know who they are. Various prevalent methods, such as API keys, OAuth tokens, or JSON Web Tokens (JWT), can be employed based on the data’s sensitivity and the desired security level. Following authentication, enforce stringent authorization protocols to regulate access to resources. Develop and implement access policies, roles, and permissions to guarantee that users and systems possess the required privileges without exceeding them.
    2. Use HTTPS (SSL/TLS) for data encryption – Data transmitted between clients and the API server should always be encrypted using HTTPS. This ensures the data remains confidential during transit and protects it from eavesdropping and man-in-the-middle attacks. Employ the latest and strongest versions of SSL/TLS protocols and keep them updated to guard against known vulnerabilities.
    3. Input validation and sanitization – Implement thorough input validation to protect against injection attacks such as SQL injection, XSS (Cross-Site Scripting), and other injection-based vulnerabilities. Validate and cleanse user-provided data to ensure the API handles only valid and expected information. Malicious actors can’t use this to exploit vulnerabilities by injecting malicious code or payload.
    4. Rate limiting and throttling- Developing rate limiting and throttling mechanisms is essential to manage the volume of requests a client can initiate within a designated time frame. These measures mitigate the risk of abuse, whether intentional or unintentional, and safeguard the API from potential overload due to an excessive number of requests, such as those associated with DDoS attacks. Adjusting rate limits according to the API’s specific characteristics and the application’s requirements is crucial for effective control and optimization.
    5. Rotation and revoking- Secrets rotation should be automatically done at least  every 90 days. If you are creating your own API, before publishing, assure that the API Key or JWT that is used has a signature that can be detected easily by secret scanners, to simplify risk mitigation due to exposure of api keys / tokens

In addition to these practices, staying informed about the latest security threats and regularly updating dependencies (such as libraries and frameworks) are essential components to protect against API security risks.


In today’s digital world, APIs are important for connecting different software programs and making them work together easily. Businesses are exposed to significant security risks due to this increased reliance on APIs. Understanding these risks and adopting robust protection measures is paramount. From inadequate authentication to injection attacks, securing APIs demands a proactive approach. Rigorous API vulnerability detection, following API security guidelines, all aligned with the architecture, helps identify vulnerabilities and fortify the system against potential threats. Best practices such as strong authentication, HTTPS encryption, input validation, rate limiting, and monitoring form the bedrock of a resilient API protection strategy.

Entro emerges as a game-changer in secrets security. Entro is the only holistic secrets management solution that protects your secrets and gives you in-depth insight into their risk levels. Explore how Entro can revolutionize your organization’s security posture. Visit Entro to embrace unparalleled cyber resilience. Safeguard your secrets, fortify your defenses, and navigate the future of secure APIs with Entro.

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