API Security: Threats, Tools, and Best Practices

What Is API Security?

API security refers to the practices and protocols that are used to protect APIs (Application Programming Interfaces) in web services, web applications, and mobile applications from misuse or malicious activity. APIs are the bridges that enable different software applications to interact and communicate with each other. They are vital in today's interconnected digital world, facilitating data exchange and functionality sharing between different systems and services.

However, while APIs offer numerous benefits, they also present major security challenges. This is because they provide an open doorway to the underlying software application, making them a prime target for cyber attackers. API security involves implementing measures to ensure that these APIs are only accessible by authorized systems, and cannot be abused or disrupted by cybercriminals.

API security is a complex field, including everything from encryption and authentication to monitoring and threat detection. The goal is to ensure that APIs are used correctly, that the data they facilitate is protected, and that any potential vulnerabilities are identified and addressed before they can be exploited.

This is part of an extensive series of guides about application security.

Why Is API Security Important? 

APIs are a foundation of the new data economy and are increasingly used by businesses to expose their services and data to the outside world. They are used in everything from mobile applications and web services to IoT devices and cloud platforms. This means that any vulnerabilities in these APIs can potentially expose a business's entire digital infrastructure to cyber threats.

APIs often expose sensitive aspects of an application to the world. They are the gateways through which data flows in and out, and as such, they are an attractive target for cybercriminals. If an API is not properly secured, it can be used to gain unauthorized access to sensitive information, disrupt services, or even take over entire systems.

Another consideration is that the regulatory landscape is evolving, and businesses are now required to comply with various data protection and privacy laws. In many cases, these regulations stipulate that businesses must implement appropriate measures to ensure the security of the data they handle, including the data that is processed through their APIs. Non-compliance can result in hefty fines and reputational damage.

Application Security vs. API Security

While both application security and API security aim to protect software applications from threats, there are some key differences between the two. Application security is a holistic approach that covers all aspects of an application, including the code, the user interface, the network connections, and the APIs. It involves a wide range of practices, such as secure coding, penetration testing, vulnerability scanning, and threat modeling.

API security focuses specifically on the APIs that an application uses. It deals with issues such as securing the data that is transmitted via the API, ensuring that only authorized users can access the API, and preventing attacks that specifically target APIs, such as DDoS attacks or injection attacks.

What Is The OWASP API Top 10? 

The Open Web Application Security Project (OWASP) is a nonprofit foundation that works to improve the security of software. Through community-led open-source software projects, hundreds of local chapters, tens of thousands of members, and leading educational and training conferences, OWASP is an important source helping technologists secure the web.

The OWASP API Top 10 is a standard awareness document for developers and web application security. It represents a broad consensus about the most critical security risks to APIs. The list is updated every several years, with the latest version being for the year 2023. Organizations, developers, and security professionals use the OWASP API Top 10 to assess the security risks associated with web applications and APIs, and to prioritize their efforts towards addressing the most pressing vulnerabilities.

Here are the OWASP top 10 API vulnerabilities as of 2023, in order of severity:

1. Broken Object Level Authorization (BOLA): This vulnerability occurs when APIs expose endpoints that handle object identifiers, creating a wide attack surface. Attackers can exploit these endpoints by manipulating the identification of an object within a request, leading to unauthorized access to data.
2. Broken Authentication: This involves incorrect implementation of authentication mechanisms, allowing attackers to compromise authentication tokens or exploit flaws to assume other users' identities. This compromises the system's ability to identify users and protect API security.
3. Broken Object Property Level Authorization: This category combines issues related to excessive data exposure and mass assignment. It focuses on the lack of or improper authorization validation at the object property level, leading to information exposure or manipulation by unauthorized parties.
4. Unrestricted Resource Consumption: APIs that do not properly manage resource consumption can be vulnerable to Denial of Service attacks or incur increased operational costs due to excessive use of resources like network bandwidth, CPU, or memory.
5. Broken Function Level Authorization: This vulnerability arises from complex access control policies with unclear separation between administrative and regular functions. Attackers can exploit these flaws to access other users’ resources or administrative functions.
6. Unrestricted Access to Sensitive Business Flows: APIs that do not adequately protect business flows can be exploited in an automated manner, potentially harming business operations.
7. Server Side Request Forgery (SSRF): This occurs when an API fetches a remote resource without validating the user-supplied URI, allowing attackers to send requests to unexpected destinations, even through firewalls or VPNs.
8. Security Misconfiguration: APIs and their supporting systems often contain complex configurations. Missed configurations or failure to follow best practices can open the door to various types of attacks.
9. Improper Inventory Management: With APIs exposing more endpoints than traditional web applications, proper and updated documentation becomes crucial. Issues like deprecated API versions and exposed debug endpoints arise from poor inventory management.
10. Unsafe Consumption of APIs: Developers sometimes adopt weaker security standards for data received from third-party APIs. Attackers target these integrated third-party services to compromise the APIs indirectly.

Other Significant API Threats 

While the OWASP API Top 10 is a great start to securing APIs, it doesn’t cover all important security threats. The list mainly focuses on the application layer, but APIs face risks from other directions as well. Here are additional important threats facing APIs

• Denial of Service (DoS) attacks: In a DoS attack, the attacker overwhelms the API with a flood of requests, causing it to become unavailable. This can disrupt the application's functionality and prevent legitimate users from accessing the services they need. A bigger threat is distributed denial of service (DDoS), in which attackers use botnets of up to millions of computers to generate fake traffic at a massive scale.
• ATOs (Account Takeovers): In an ATO attack, the attacker gains control of a user's account. While this could happen through application-level vulnerabilities, it can also be done via social engineering or other methods that exploit human weaknesses. Once they have access to the account, they can carry out fraudulent activities, such as making unauthorized transactions or stealing personal data.
• Inventory Denial Attacks: Inventory denial attacks are a specific type of attack that targets eCommerce applications. In these attacks, the attacker uses the API to add large quantities of items to their shopping cart, causing the items to appear as out of stock for other users. This can result in lost sales and damage to the business's reputation.
• API sprawl and shadow APIs: API sprawl is a phenomenon where the number of APIs in an organization grows to the point where it becomes difficult to manage and secure them all effectively. Shadow APIs are a particular risk, where an organization uses or exposes APIs that are unknown to development or IT teams. This can lead to increased security risks, as it becomes harder to ensure that all APIs are properly secured and that vulnerabilities are identified and addressed.

Learn more in our detailed guide to shadow api

Tzvika Shneider

CEO, Pynt

Tzvika Shneider is a 20-year software Security industry leader with a robust background in product and software management.

Tips from the expert

• Implement fine-grained access control: Use a combination of role-based and attribute-based access control to ensure only authorized users have the right level of access.
• Regularly update API documentation: Keep your API documentation up-to-date to avoid security gaps from deprecated or undocumented endpoints.
• Conduct third-party security audits: Periodically invite external security experts to audit your APIs for an unbiased assessment.
• Implement rate limiting and throttling: Protect your APIs from abuse by limiting the number of requests a client can make in a given time frame.
• Use API gateways for centralized security: API gateways can enforce security policies, manage traffic, and provide analytics for better security management.

REST API vs. SOAP vs. GraphQL Security 

There are several types of APIs, and the type of API you're using can significantly impact your security posture. Three of the most commonly used APIs are REST, SOAP, and GraphQL:

REST APIs are the most commonly used type of API due to their simplicity and scalability. Common security vulnerabilities in REST APIs include Cross-Site Request Forgery (CSRF), Injection attacks, and insecure direct object references. To secure REST APIs, you should use HTTPS for secure communication, validate and sanitize input data, and implement proper authentication and authorization mechanisms.

SOAP APIs have built-in security features, making them generally more secure than REST APIs. They use the WS-Security standard, which provides a range of security features such as message encryption, integrity, and authentication. However, SOAP APIs are more complex and less flexible than REST APIs, which can be a disadvantage in certain scenarios.

GraphQL APIs are relatively new compared to REST and SOAP APIs. They provide a more efficient way to query data, but this comes with its security challenges. Common security issues in GraphQL APIs include insecure direct object references (IDOR), mass assignment, and rate limiting. To secure GraphQL APIs, you should limit the depth and complexity of queries, implement proper authentication and authorization, and use query whitelisting.

Learn more in our detailed guide to api security standards

What Are API Security Tools and Solutions?

There are many tools and solutions available to help organizations enhance their API security. These tools provide functionalities such as vulnerability scanning, threat modeling, and security monitoring, among others.

API security tools can be broadly categorized into two types: static and dynamic: 

• Static API security tools, also known as Static Application Security Testing (SAST) tools, analyze the source code of your APIs to identify potential security vulnerabilities. They provide a deep understanding of your API's security posture and can be used early in the development lifecycle.
• Dynamic API security tools, also known as Dynamic Application Security Testing (DAST) tools, test your APIs in a running state to identify security vulnerabilities. They simulate attacks on your APIs and monitor their behavior to detect anomalies. 

There are several other important aspects of API security:

• Security test automation: Integrating with API development tools and automatically testing APIs during their development stages.
• CI/CD integration: Integrating API security with CI/CD pipelines and tools to ensure every iteration of API development undergoes security testing.
• API discovery: Discovering shadow APIs and third-party APIs across the organization and scanning them for vulnerabilities.
• Compliance: Ensuring APIs are compliant with regulations and standards

Related content: Read our guide to api compliance

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Key API Security Capabilities and Components 

Let’s explore the key capabilities of API security solutions in more detail.

API Inventory and Discovery

One of the most crucial aspects of API security is having an accurate inventory of all your APIs because you can't protect what you don't know. Many organizations have hundreds or even thousands of APIs, making it challenging to keep track of them all. This is where API inventory and discovery tools come into play.

API inventory and discovery tools help you identify all your APIs, both public and private. They provide a centralized view of all your APIs, along with detailed information such as their endpoints, methods, and data types, among others. This not only helps you understand your API landscape better but also enables you to identify potential security risks and take appropriate measures to mitigate them.

These tools also help you keep your API inventory up to date. As your organization grows and evolves, so do your APIs. New APIs are developed, existing ones are modified, and old ones are deprecated. API inventory and discovery tools automatically detect these changes and update your API inventory accordingly.

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Pynt performs API inventory and discovery primarily through:

• Automated Scanning: Utilizes functional tests to perform automated API security dynamic scan, identifying both documented and undocumented APIs.
• Integration with API Gateways and Management Platforms: Gathers information on APIs routed through platforms like AWS API Gateway, aiding in comprehensive discovery.
• Leveraging Documentation: Utilizes existing API documentation, such as Swagger or OpenAPI specifications, to catalog and understand APIs.
• Continuous Discovery: Regularly updates API inventory to capture new and modified endpoints, ensuring an up-to-date overview.
• Categorization and Risk Assessment: Classifies APIs based on function, data sensitivity, and exposure, and evaluates potential security and compliance risks.

Learn more about Pynt’s API Inventory and Discovery

API Posture Management

API posture management involves assessing your APIs' security status and implementing measures to improve it. This involves various activities such as vulnerability scanning, threat modeling, and compliance monitoring, among others.

API posture management tools help you automate these activities. They continuously scan your APIs for vulnerabilities, model potential threats, and monitor your APIs' compliance with various security standards and regulations. This helps you identify and fix security issues before they can be exploited, thereby enhancing your API security.

These tools provide detailed reports and dashboards, giving you a clear view of your APIs' security posture. This allows you to track your APIs' security status over time, understand trends, and make informed decisions to improve your API security.

Related content: Read our guide to api scanning

API Runtime Protection

API runtime protection involves monitoring and controlling API requests and responses in real-time to prevent unauthorized access or data breaches. This layer of security is essential because APIs, by their very nature, expose an application's internal workings to the outside world.

The central aspect of API runtime protection is ensuring that only authorized users have access to the APIs. This is typically achieved through authentication and authorization mechanisms such as OAuth or OpenID Connect. Additionally, protection against API-specific attacks such as SQL Injection, Cross-Site Scripting (XSS), or Denial-of-Service (DoS) is crucial.

Protecting APIs at runtime also involves monitoring and limiting the rate of API requests. This not only prevents potential DoS attacks but also helps maintain the application's performance and stability by preventing overuse or abuse of the APIs.

Learn more in our detailed guide to API protection (coming soon).

API Security Testing

Unlike traditional security testing methods that focus on the user interface level, API security testing probes deeper into the application, examining the APIs for potential security vulnerabilities.

The first step usually involves understanding the API's structure and functionality. This requires analyzing the API's specification (such as the OpenAPI Specification) and the data it handles. 

Once the API's workings are understood, various testing techniques can be employed. These include fuzz testing (sending random, unexpected data to the API to see how it reacts), boundary value analysis (testing the API's response to values at the extremes of what it should accept), and penetration testing (attempting to 'hack' the API to uncover potential vulnerabilities).

Pynt's API security testing incorporates:

• Automated Dynamic Scanning: Real-time traffic analysis for immediate vulnerability detection.
• Context-Aware Analysis: Tailored security assessments based on each API's unique context.
• Seamless DevOps Integration: Embedding into CI/CD pipelines for continuous 'shift-left' testing.
• Rapid and Efficient: Designed for quick deployment, delivering results in a short amount of time.
• Minimized False Positives: Advanced algorithms to reduce incorrect threat identifications.
• Developer-Friendly: Easy integration, ensuring a smooth user experience for developers.

Learn more about Pynt’s API Security Testing

API Governance

API governance is an overarching component of API security. It involves defining and implementing policies, procedures, and standards for API usage and management. This not only helps maintain API security but also ensures the APIs are used effectively and efficiently, delivering maximum value to the organization.

API governance policies typically cover various aspects of API usage, such as authentication and authorization, rate limiting, data privacy, and error handling. Also important is monitoring and enforcing these policies. This can be achieved through various means, such as logging and auditing API usage, implementing API gateways to control and monitor API traffic, and using API management platforms to manage and enforce the API governance policies.

Learn more in our detailed guide to api governance

API Security Best Practices 

Classify Data Managed by APIs

Data classification involves categorizing the data handled by the APIs based on its sensitivity and then applying appropriate security measures based on these categories.

The first step in data classification is to understand what data the APIs handle. This involves analyzing the API's specification and the data it processes. Once the data is understood, it can be categorized into different sensitivity levels, such as public, internal, confidential, or restricted.

Once the data is classified, appropriate security measures can be applied based on its sensitivity. For example, public data may not require any special security measures, while confidential data may require encryption, strict access control, and rigorous auditing.

Implement Access Control

Implementing robust access control involves ensuring that only authorized users can access the APIs and that they can only perform actions they are permitted to.

Access control can be achieved through various means, such as using OAuth or OpenID Connect for authentication and authorization, implementing Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC) to control what actions a user can perform, and using API keys to identify and authenticate API users.

Related content: Read our guide to api exposure

Validate Input Parameters

Parameter validation involves checking the data sent to the APIs (the parameters) to ensure they are correct and safe.

Parameter validation can help prevent various API attacks, such as SQL Injection or Cross-Site Scripting (XSS). These attacks involve sending malicious data to the APIs in an attempt to exploit potential vulnerabilities. By validating the parameters, you can ensure they do not contain any harmful data.

Parameter validation should be implemented for all APIs, regardless of their exposure level or functionality. It should also be applied to all types of parameters, whether they are sent in the URL, the query string, the headers, or the body of the API requests. By validating the parameters, you can significantly enhance your API security, preventing potential attacks and maintaining the integrity and reliability of your APIs.

Learn more in our detailed guide to api attacks

Encrypt API Requests and Responses

Encrypting the data sent to and from the APIs is an effective way to prevent unauthorized access or tampering. Encryption can be achieved through various means, such as using HTTPS for secure API communication, implementing Transport Layer Security (TLS) to encrypt the data in transit, and using encryption algorithms such as AES or RSA to encrypt the data at rest.

Encrypting API requests and responses not only protects the data from potential eavesdropping or tampering but also helps maintain the privacy and integrity of the data. By encrypting your API communication, you can ensure the security of your data, even if it is intercepted or accessed by unauthorized parties.

Aim for Continuous API Security

Lastly, continuous security is an overarching best practice in API security. It involves continuously monitoring, testing, and improving the API security measures to ensure they remain effective in the face of evolving threats and changing API usage patterns.

Continuous security can be achieved through various means, such as continuously monitoring and analyzing API security events, regularly conducting API security testing to uncover and fix potential vulnerabilities, and integrating automated security tools into CI/CD pipelines to continuously check and enforce the API security measures.

Continuous security requires constant vigilance, regular reviews, and continuous improvement to ensure the APIs remain secure. It can help keep your APIs secure, even as the threat landscape evolves and your APIs grow and change.

Learn more in our detailed guide to API security best practices

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API Security with Pynt

Pynt's approach to API security emphasizes a 'shift-left' methodology, focusing on early discovery and resolution of vulnerabilities. This proactive stance in the software development life cycle allows for:

• Early Detection: Identifying API vulnerabilities early in the development process, reducing potential security risks.
• Leverages functional tests to detect complex business logic scenarios, providing targeted security insights.
• Seamless Integration: Facilitating easy integration with existing development tools and pipelines, enhancing developer productivity without compromising security.
• Comprehensive API Discovery: Automated discovery of APIs, ensuring complete visibility from development to production, crucial for identifying shadow APIs and other hidden risks.

These aspects collectively enhance the overall security posture by addressing API vulnerabilities at their inception, rather than as an afterthought.

Related content: Read our guide to api discovery

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See Additional Guides on Key Application Security Topics

Together with our content partners, we have authored in-depth guides on several other topics that can also be useful as you explore the world of application security.

API Security Testing

Authored by Pynt

• API Security Testing
• API Security Scanning: Process, Tools, and Best Practices

Operating System Security

Authored by Sternum 

• Memory Corruption: Examples, Impact, and 4 Ways to Prevent It 
• What Is the Double Free (CWE-415)?
• 7 Characteristics of Embedded Systems and What the Future Holds 

Cyber Attack

Authored by Imperva

• What is a Cyber Attack | Types, Examples & Prevention 
• What is Ransomware | Attack Types, Protection & Removal 
• What is Social Engineering | Attack Techniques & Prevention Methods