What is API Security? Key Threats, Tools & Best Practices

Key Takeaways

API security protects against unauthorized access, data leaks, and service disruption by securing how APIs are built, deployed, and managed.
OWASP’s API Top 10 identifies Broken Object Level Authorization, Broken Authentication, and Resource Consumption as the most critical API vulnerabilities. Pynt’s analysis compares OWASP’s list with real-world API security trends.
Real-world breaches like those at T-Mobile and Peloton highlight the dangers of missing authentication, weak rate limiting, and exposed endpoints.
Accurate API inventory, runtime protection, and continuous security monitoring are essential for mitigating risks across modern, distributed API ecosystems.
Pynt’s shift-left dynamic scanning integrates into CI/CD pipelines, enabling early vulnerability detection with reduced false positives and minimal developer friction.

What Is API Security?

API security is the practice of protecting Application Programming Interfaces from attacks, misuse, and unauthorized access. It focuses on how APIs are built, deployed, and managed to prevent data leaks and system exposure. The goal is to keep APIs functioning safely without risking sensitive information or service integrity.

What Is API-to-API Security?

API-to-API security addresses the protection of interactions between two or more APIs. These exchanges often occur behind the scenes between internal services, making them harder to observe and control. Strong authentication, encrypted communication, and strict access policies are essential to prevent unauthorized data sharing or tampering between connected APIs.

Why Is API Security Important?

APIs are important for modern software, but without proper security, they expose critical systems and data to serious risks. Here’s why API security matters:

APIs expose sensitive data: APIs handle personal, financial, and business-critical information. If not secured, attackers can extract or manipulate this data.
They are prime attack targets: APIs are directly accessible over the internet, making them attractive entry points for attackers aiming to disrupt services or breach systems.
A single flaw can compromise entire systems: Weaknesses in one API can lead to lateral movement, privilege escalation, or complete application takeover.
Business continuity depends on them: Downtime caused by API abuse or denial-of-service attacks can lead to service disruption, lost revenue, and user frustration.
Compliance requirements demand it: Regulations like GDPR, CCPA, and HIPAA require secure handling of personal data, which includes data processed through APIs.
Growing API ecosystems increase risk: As organizations adopt microservices and integrate with third-party services, the API attack surface grows, requiring continuous monitoring and protection.

Application Security vs. API Security

While both aim to protect systems from malicious activity, application security and API security operate at different layers and require distinct approaches. Understanding their differences helps prioritize the right controls and tools based on where the risks lie. Here’s how they compare across key dimensions:

Category	Application Security	API Security
Scope	Covers the entire application stack, including front-end, back-end, and data layers.	Focused specifically on securing APIs and their interactions with other systems.
Focus Areas	Secure coding, UI logic, data validation, session handling, and overall architecture.	Endpoint authentication, access control, data flow validation, and rate limiting.
Primary Risks	SQL injection, XSS, insecure session management, and business logic flaws.	Unauthorized API access, data exposure, abuse of endpoints, and injection attacks.
Data Exposure	Typically limited to what’s shown in the user interface.	Direct access to internal services or databases, often bypassing UI restrictions.
User Authentication	Session-based authentication, typically tied to user credentials and browser sessions.	Token-based mechanisms like OAuth 2.0 or API keys with fine-grained scopes.
Threat Detection	App-level logging, behavior monitoring, and post-deployment scans.	Real-time traffic inspection, anomaly detection, and API-specific monitoring.

OWASP API Security Top 10 Risks

The OWASP API Top 10 is a widely recognized list of the most critical API security threats. Updated in 2023, it helps teams identify common weaknesses in API design and prioritize remediation efforts to reduce risk.

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

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.
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.
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.
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.
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.
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.
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.
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.
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.
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.

Good to Remember

OWASP is a valuable baseline but your real API risks depend on architecture, auth design, and traffic patterns. Always validate against real usage, not just theoretical lists.

Pynt vs OWASP: Top 10 API Vulnerabilities

Explore the comparison between OWASP and Pynt API Top 10 Vulnerabilities for 2023. While both lists address common API risks like authorization flaws and misconfigurations, Pynt also identifies emerging threats such as Missing Authentication, Injection, and Local File Access.

#	OWASP API Top 10 2023	PYNT API Top 10 2023
API1	Broken Object Level Authorization (BOLA)	Missing Authentication
API2	Broken Authentication	Injection
API3	Broken Object Property Level Authorization	Broken Object Level Authorization (BOLA)
API4	Unrestricted Resource Consumption	Broken Authentication
API5	Broken Function Level Authorization	Security Misconfiguration
API6	Unrestricted Access to Sensitive Business Flows	Mass Assignment
API7	Server Side Request Forgery	Broken Function Level Authorization
API8	Security Misconfiguration	Unrestricted Resource Consumption
API9	Improper Inventory Management	Server Side Request Forgery
API10	Unsafe Consumption of APIs	Local File Access

Sources: OWASP Top 10 API Vulnerabilities, 2023, Pynt Top 10 API Security Vulnerabilities Research Report, 2023

Other Key API Security Vulnerabilities

While the OWASP API Top 10 highlights critical risks, APIs also face additional threats beyond that list. These issues often target operational gaps, business logic, and evolving technologies.

Denial of Service (DoS) attacks: Attackers overwhelm APIs with excessive requests, making them unresponsive to legitimate users. Distributed versions (DDoS) amplify the effect by using botnets to flood services at scale.
Account Takeovers (ATOs): Through credential stuffing, phishing, or social engineering, attackers gain control of legitimate accounts and use them to access APIs, make fraudulent transactions, or extract data.
Inventory denial attacks: Common in eCommerce, these attacks involve reserving or hoarding product inventory through APIs, preventing real customers from completing purchases and causing business loss.
API sprawl and shadow APIs: As organizations grow, undocumented or forgotten APIs emerge. These shadow APIs often lack security oversight, increasing the chance of exposure and attack.
AI and API security: AI-driven systems increasingly rely on APIs for input and output. If attackers manipulate the data sent through APIs, they can alter model behavior, trigger incorrect predictions, or extract proprietary training data. AI APIs also face risks like prompt injection, model inversion, and inference manipulation.

Real-World Examples of API Exploits

API vulnerabilities have led to serious data breaches across industries. These incidents highlight how poor authentication, missing access controls, or exposed endpoints can open the door to major compromise.

T-Mobile API Breach Exposed Data of 37 Million Customers

T-Mobile confirmed in 2023 that a malicious actor exploited one of its APIs to collect personal data from over 37 million customer accounts. The exposed information included names, emails, phone numbers, and billing details. The breach stemmed from an unauthenticated API that allowed access to customer data without proper rate limiting or identity checks.

Peloton API Exposed Private User Data Without Authentication

In 2021, Peloton’s public API was found to expose user account data, including location, gender, and workout metrics, even for profiles marked as private. The API failed to enforce proper authentication or authorization, which allowed anyone to query and retrieve information from millions of user accounts. The issue raised serious concerns about privacy controls and access validation across fitness platforms.

Facebook Graph API Flaw Exposed Access Tokens and Profile Data

In 2018, Facebook disclosed a vulnerability in its Graph API that allowed attackers to steal access tokens and scrape personal profile data. The issue arose from overly permissive access controls, allowing attackers to pivot from one account to another in their network. Over 50 million users were affected.

Google+ API Bug Leaked Private Profile Details to Third Parties

Google identified a critical vulnerability in its People API back in 2018 that exposed private profile fields - such as emails, occupations, and gender - to 438 third-party applications. Approximately 500,000 users had their data exposed, even though it was not marked as publicly accessible.

Major API security breaches: T-Mobile (2023), Peloton (2021), Facebook (2018), Google+ (2018) with user impact numbers.

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

Build an Accurate API Inventory

Security teams cannot secure what they cannot see. Building an accurate inventory of all API assets is a foundational step in protecting the API landscape. This includes every known and unknown API across environments, covering legacy services, third-party integrations, and internal tools. A reliable inventory helps identify exposed API endpoints, track the full API lifecycle, and align protection strategies with the level of data sensitivity each interface manages. Keeping this catalog current reduces blind spots and supports compliance, testing, and audit efforts.

Monitor API Activity and Audit Logs

Continuous visibility into API activity is critical for detecting suspicious behavior. Logging each API call with its associated metadata, including the endpoint accessed, the requesting user, and the time of the call, creates a valuable audit trail. These logs make it easier to uncover signs of API abuse, such as excessive call volumes or unauthorized data access attempts. By centralizing and analyzing these records - often using tools like Postman, Kong, or runtime observability platforms - security teams can improve incident response, reduce dwell time, and reinforce web API security policies in real time.

Enforce Rate Limiting and Throttling

High-frequency API traffic often signals attack attempts rather than legitimate use. Without rate limiting, malicious actors can overwhelm APIs with automated traffic or flood sensitive endpoints with repeated API calls. Throttling API access according to user roles, origin, and request type adds an important layer of control. This practice helps prevent API abuse, protects resource availability, and supports REST API security standards. Enforcing rate controls also reduces the impact of denial-of-service attacks and narrows the window for credential stuffing campaigns to succeed.

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

API security best practices like data classification, access control, input validation, building an accurate API inventory, monitoring, and rate limiting.

How to Secure Back-End APIs?

Back-end APIs often serve as the core infrastructure for internal services, data pipelines, and microservice communication. While not exposed directly to end users, these APIs still face serious security risks. Misconfigured API endpoints, missing authentication layers, and unchecked API calls can lead to unauthorized access, data leakage, or full system compromise.

Securing them requires deliberate design choices and proactive controls:

Authenticate every request: Never assume back-end APIs are safe by design. Use mutual TLS, signed tokens, or identity-aware proxies to validate each call.
Limit access scopes: Apply the principle of least privilege across roles, services, and systems to reduce the chance of unauthorized data access.
Conduct regular API testing: Use automated scanners and runtime observability tools to identify logic flaws or integration errors that surface during the API lifecycle.
Encrypt all communication: Use TLS 1.2 or above for all connections to prevent interception of sensitive data, even within trusted environments.
Monitor for abuse patterns: Track anomalies in usage that may point to API abuse, excessive API calls, or privilege escalation attempts.

Tzvika Shneider

CEO, Pynt

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

Expert Tip: Boost API Security with These Actionable Steps

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.

Different Types of API Security: REST API vs SOAP vs GraphQL Security

Different API architectures come with varying models of security, strengths, and risks. Comparing them side by side helps teams choose the right protocol based on their use case and security requirements.

Category	REST API Security	SOAP Security	GraphQL Security
Authentication & Authorization	Typically uses OAuth 2.0 (with adoption moving toward OAuth 2.1), API keys, or JWT. Fine-grained control depends on implementation.	Built-in support for WS-Security, including XML Signature and XML Encryption.	Relies on OAuth or token-based auth. Needs layered validation for complex queries.
Data Exposure Risk	Can overexpose data via loosely defined endpoints. Input validation is critical.	Responses are tightly structured, reducing accidental data exposure.	High risk of over-fetching or exposing nested data unless queries are restricted.
Common Threats	Injection attacks, CSRF, excessive data exposure, and broken access control.	XML-based attacks like XML injection, schema poisoning, and parser exploits.	Injection attacks, denial of service via complex queries, and introspection abuse, where attackers query the API schema to reveal available fields or operations.
Security Complexity	Moderate to high, depending on design. Requires strong endpoint governance.	High due to verbosity and strict protocol rules, but also more structured.	High. Requires careful query limiting, validation, and rate limiting.
Tooling & Standards	Widely supported by modern security tools, including API gateways and DAST scanners.	Fewer modern tools, but strong support for enterprise-grade SOAP toolkits.	Still evolving. Some tools now support GraphQL-specific security scanning.

What is API Security Management?

API security management is the process of protecting APIs from threats, ensuring they function securely while handling sensitive data. It involves implementing security measures to prevent unauthorized access, data breaches, and cyberattacks.

Key Components of API Security Management

Authentication & Authorization – Control access with OAuth 2.0, JWTs, OpenID Connect, and RBAC.
Firewalls & WAFs – Use Web Application Firewalls (WAFs) and network firewalls to block malicious traffic.
Data Encryption – Protect data in transit and at rest with TLS/SSL encryption.
Input Validation – Sanitize user input to prevent SQL injection and XSS attacks.
Rate Limiting – Restrict request frequency to prevent abuse and overload.
Monitoring & Testing – Test APIs to track API vulnerabilities and fix issues.

An API gateway helps enforce these security measures, acting as a protective layer between clients and APIs.

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

Key Features of API Security Solutions

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.

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.

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

Securing APIs Early: Pynt’s Shift-Left Approach

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.

Comparison table of Pynt API Security Testing vs. Generic DAST tools on automation, accuracy, CI/CD integration, and ease of use.

Conclusion

APIs are at the core of modern digital services, but their expanding complexity demands stronger security measures. Misconfigurations, weak authentication, and unmonitored endpoints can expose systems to serious threats that affect data integrity, service availability, and customer trust.

Organizations can strengthen their API defenses by applying proven security best practices, maintaining a complete and accurate API inventory, and using specialized tools for monitoring, testing, and access control. Securing APIs is not a one-time task but an ongoing effort that must evolve alongside the technologies and threats shaping the software ecosystem. As APIs continue to power AI systems, mobile applications, and cross-platform integrations, protecting them is more than a technical necessity. It is a foundational step toward building lasting digital trust and ensuring resilience in a constantly shifting threat landscape.

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FAQs

What are API security standards?

API security standards guide how APIs should be secured across their lifecycle, from design to deprecation. Key standards include:

OWASP API Security Top 10: Helps identify and prioritize common API security risks
OAuth 2.0 / 2.1 and OpenID Connect: For secure authorization and identity federation
TLS 1.2+: Ensures encrypted communication between clients and servers
NIST SP 800-53 and ISO/IEC 27001: Establish broad security and compliance frameworks
OpenAPI Specification (OAS): Can define security requirements directly within API contracts

What is a zombie API?

A zombie API is an outdated or deprecated API endpoint that remains publicly accessible despite no longer being maintained or documented. These forgotten interfaces often arise from microservice sprawl or incomplete decommissioning in CI/CD pipelines. Since they typically escape version control and security testing, they become high-risk targets for exploitation.

How to secure an API without authentication?

Securing an API without authentication is only appropriate for low-risk scenarios, such as open data feeds or internal systems that do not handle sensitive information. In these cases, security relies on layered compensating controls. Rate limiting, throttling, and IP filtering can restrict traffic volume and origin, while limiting endpoints to read-only access ensures that no data can be modified. Input validation and schema enforcement help prevent injection and misuse.

Logging every request adds visibility into usage patterns and supports anomaly detection. Finally, using API keys or allow lists—even without full authentication—can help control access in a basic but effective way.

What is the API security lifecycle?

The API security lifecycle involves securing APIs across all phases of development and use:

Design: Define access scopes, threat models, and data classification
Development: Implement secure coding practices, input sanitization, and secure token handling
Deployment: Enforce authentication, authorization, encryption, and rate limiting
Monitoring: Track usage patterns, detect anomalies, and log traffic for analysis
Retirement: Revoke access, decommission unused endpoints, and update the API inventory

How do you protect an API with SSL?

APIs are protected using TLS (the modern version of SSL) through the following:

Enforce HTTPS and disable outdated protocols like TLS 1.0 or SSLv3
Use valid TLS 1.2 or 1.3 certificates issued by a trusted certificate authority
Enable HSTS headers to prevent downgrade attacks
Rotate, revoke, and renew certificates on a scheduled basis
In sensitive environments, implement mutual TLS (mTLS) for client-server authentication

How do API gateways handle security internally?

API gateways serve as centralized points of enforcement for API traffic. They help secure APIs by:

Authenticating users via OAuth 2.0, JWT tokens, or API key
Enforcing rate limits, quotas, and IP restrictions
Validating request schemas and rejecting malformed payloads
Applying access control policies to route traffic securely
Logging and analyzing request data for threat detection and alerting
Optionally integrating with WAFs for attack pattern recognition (e.g., SQLi, XSS)

How are APIs encrypted?

APIs use encryption to protect data both in transit and at rest:

In transit: Secured via TLS 1.2 or 1.3, which encrypts communication between client and server
At rest: Protected using encryption methods such as AES-256 at the disk, database, or application layer

What is API security scanning?

API security scanning is the process of testing APIs to identify security flaws throughout their lifecycle. It combines early-stage testing during development with continuous monitoring in production environments.

One method focuses on shift-left testing, where simulated attacks are used during the build phase to identify issues such as broken authentication, excessive data exposure, or insecure logic. The other involves real-time scanning of live API traffic to detect threats such as abuse patterns, unauthorized access attempts, or anomalous behavior.

Together, these approaches reduce risk, prevent data leaks, and help ensure APIs remain secure from development through deployment and beyond.

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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

Penetration Testing