What is API security?
API security is the practice of protecting application programming interfaces from threats throughout their entire lifecycle. This means implementing authentication, authorization, encryption, and monitoring controls to prevent unauthorized access and data exposure. APIs face threats from both external attackers and internal misconfigurations, making security controls essential at every stage from design through deprecation.
APIs sit at the intersection of application, information, and network security. Unlike traditional web applications, APIs expose business logic and data pathways directly, which means a single weak endpoint can compromise multiple systems.
Effective API security addresses several interconnected concerns:
Access control: Ensuring only authorized users and systems can reach specific endpoints
Content validation: Verifying that incoming requests conform to expected formats and reject malicious payloads
Rate limiting: Preventing abuse by capping request volume per client
Monitoring: Detecting anomalies and unauthorized access attempts in real time
Advanced API Security Best Practices [Cheat Sheet]
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Why is API security important?
APIs have become the primary attack vector in modern applications because they expose business logicand data pathways that traditional perimeter defenses cannot protect. When an API is compromised, the blast radius extends far beyond a single application.
The business consequences are severe. Broken or exposed APIs consistently rank among the top causes of major data breaches, often leaking significantly more data than traditional security incidents. Without proper controls, organizations face data theft, system compromises, and regulatory violations that can take months to remediate.
Effective API security preserves data confidentiality, ensures authorized-only access, and maintains data integrity throughout transmission and storage.
OWASP API security: Top 10 risks
The OWASP Top 10 is a list of security risks curated to help developers design applications with security in mind. Let's take a look at how these points relate to APIs:
1. Broken object-level authorization
Broken object-level authorization occurs when an API fails to verify that a user has permission to access a specific object. Attackers exploit this by manipulating object IDs in API requests to access data belonging to other users. In 2018, the United States Postal Service experienced this vulnerability due to weak access controls, compromising over 60 million users' data.
2. Broken authentication
Without strong authentication mechanisms, it can be possible for attackers to gain access to APIs and use them for malicious ends. In June 2021, an exposed API lacking proper authentication was exploited, compromising the personal data of approximately 1.3 million individuals. Simple token or key authentication could have thwarted this attack.
3. Broken object-property-level authorization
Developers occasionally return superfluous data, assuming APIs will be accessed solely by authenticated users. This issue, which focuses on improper authorization at the object property level, combines previous OWASP categories like Excessive Data Exposure and Mass Assignment. However, attackers can exploit this excess data. HealthEngine suffered from this vulnerability in their feedback API, leaking over 59,000 patients' personal information.
4. Unrestricted resource consumption
Unrestricted resource consumption occurs when APIs lack proper rate limiting and resource controls. Each API request consumes network bandwidth, memory, and compute resources. Without limits, attackers can overwhelm APIs with excessive requests, causing service outages for legitimate users. In cloud environments, this also translates to runaway infrastructure costs that can accumulate before teams detect the abuse.
5. Broken function-level authorization
Many systems have access control policies that are complex. If function-level authorizations aren't implemented, attackers can access unauthorized functions. A recent case in September 2022 saw an attacker infiltrate Uber's IT infrastructure due to this API vulnerability.
6. Unrestricted access to sensitive business flows
Excessive access to critical business flows can disrupt operations. In 2011, CITI suffered a data breach affecting 350K North American cardholders due to an attack that manipulated its business flows.
7. Server-side request forgery (SSRF)
Server-side request forgery occurs when an API fetches data from a user-supplied URL without proper validation. Attackers exploit this to make the API request internal resources that should be inaccessible from outside. In cloud environments, SSRF is particularly dangerous because attackers can target cloud metadata services to steal credentials and escalate access across the infrastructure.
8. Security misconfiguration
Insecure configurations can lead to various API attacks that expose sensitive data and gain unauthorized access. These vulnerabilities arise from myriad factors, such as missing patches, outdated systems, or exposed error details.
9. Improper inventory management
With APIs often exposing more endpoints than traditional web applications, maintaining accurate documentation is essential. Poor inventory management can result from insecure storage, weak encryption, or inadequate access controls.
10. Unsafe consumption of APIs
API consumption often hinges on the trust developers place in third-party responses. Many developers believe third-party APIs, especially those offered by well-known companies, are inherently secure. This misplaced trust can lead to vulnerabilities. Instead of directly targeting your APIs, attackers might exploit these third-party integrations. Incidents, like the SSRF attacks, can manifest because of inadequate validation and sanitization of responses.
By understanding these risks and implementing proper security measures, organizations can significantly mitigate the potential threats associated with APIs. Visit OWASP's API Security Top 10 to get a detailed breakdown of each risk.
API security for SOAP, REST, and GraphQL
Each of the three primary API architectures, SOAP, REST, and GraphQL, has its own unique security implications.
| API Architecture | Security Implications |
|---|---|
| SOAP API Security | SOAP is a streamlined, XML-based messaging protocol designed for exchanging structured data in decentralized computer networks. It's adaptable across various protocols such as HTTP and SMTP. SOAP's security layers incorporate both transport layer security (like HTTPS) to encrypt data in transit and message-level security, including XML digital signatures, to uphold message integrity. By following Web Services (WS) specifications, which offer standardized guidelines, SOAP provides security features such as WS-ReliableMessaging for enhanced error handling. |
| REST API Security | REST APIs employ JSONs for data representation and rely on HTTP/s for data transfers, streamlining the development process. Since REST lacks inherent security mechanisms, its security is contingent upon the design of the API. Implementing security measures in data transmission, deployment, and client interactions is essential. Typically, REST APIs rely on protocols such as HTTPS and employ token-based authentication to enhance security. |
| GraphQL API Security | GraphQL, an open-source API language, functions both as a query language and a runtime for query execution. Its strictly typed schema ensures data consistency. However, its flexibility can be a double-edged sword: complex, unfiltered queries could lead servers astray, potentially running malicious requests. Adopting security practices like throttling, setting query depth limits, and implementing query timeouts can mitigate these vulnerabilities. |
Is your company developing applications with GenAI? Just like any other multi-tenant service, GenAI-incorporating applications can suffer from traditional API vulnerabilities. Learn how to deploy generative AI models as part of your multi-tenant cloud apps securely.
10 API security best practices
Securing APIs requires a multi-layered approach that addresses authentication, data protection, and threat monitoring. These API best practices provide proven strategies to eliminate common vulnerabilities and build robust API defenses against evolving threats.
1. Discover and inventory all APIs
Your API security tool should offer and inventory of all APIs that are detected and effectively exposed to internet
Shadow APIs create dangerous blind spots that attackers actively exploit. These undocumented endpoints, often created during development or by teams operating outside formal processes, typically lack security controls entirely. You cannot secure APIs you do not know exist, which makes automated discovery the foundation of any API security program.
Automated discovery tools continuously scan your environment to detect all APIs, including endpoints, parameters, data types, and third-party integrations. This comprehensive inventory enables you to apply security policies consistently and prioritize high-risk APIs for immediate attention.
2. Identify API risks and vulnerabilities
Risk identification means systematically evaluating APIs for vulnerabilities across their entire lifecycle. This proactive approach uncovers security flaws before attackers can exploit them.
Assessment should be comprehensive. Evaluate APIs against OWASP's top API risks, including broken authentication and injection vulnerabilities. Use automated scanners and penetration testing to detect configuration flaws, code weaknesses, and dependency issues.
Third-party APIs require special attention since developers tend to trust data from these sources more than user input, introducing risks beyond your direct control. Regular monitoring ensures integrated APIs maintain security standards.
3. Encrypt
Encrypt all data in transit using TLS 1.2 or higher, and consider encrypting sensitive fields within API responses for defense in depth. Even if an attacker intercepts traffic, properly implemented encryption renders the data unusable.
Review your encryption settings regularly to ensure compliance with modern standards. Avoid outdated protocols like TLS 1.0 and 1.1, which contain known vulnerabilities. Implement key rotation practices and store encryption keys separately from the data they protect.
4. Implement strong authentication and authorization
Strong authentication and authorization form the backbone of API security by controlling who can access your APIs and what they can do.
Authentication verifies identity using methods like OAuth 2.0 tokens to ensure only legitimate users and systems gain access. Authorization controls permissions through role-based access control (RBAC) or attribute-based access control (ABAC) to enforce granular restrictions on API operations.
Ongoing maintenance is essential. Regularly audit access controls, rotate API keys and tokens, and implement multi-factor authentication for sensitive operations to prevent unauthorized access and privilege escalation.
5. Use rate limits and throttling
Rate limiting prevents abuse by capping the number of API calls a client can make within a set timeframe. This helps protect against denial-of-service (DoS) and distributed denial-of-service (DDoS) attacks that can disrupt services. Throttling adds an additional layer of API protection by slowing down excessive requests to avoid overwhelming the system.
Implement customized rate limits for different user roles or API clients to balance performance and security. Regularly monitor and adjust these thresholds based on usage patterns to ensure legitimate users are not inadvertently blocked while protecting your API from abuse.
6. Use an API gateway
An API gateway acts as a centralized enforcement point for managing and securing API traffic. It handles authentication, input validation, rate limiting, and request routing to backend services. Modern gateways often integrate with Web Application Firewalls to protect against injection attacks and other common threats.
However, gateways alone are insufficient. They must be properly configured and continuously monitored. A misconfigured gateway can create a false sense of security while leaving APIs exposed. Consolidating security policies within a gateway reduces complexity, but you still need visibility into what happens beyond the gateway at the application layer.
7. Validate all input data
Input validation ensures that APIs only accept data that adheres to predefined formats and expected types. Rejecting malformed or unexpected inputs protects against injection attacks, buffer overflows, and other exploit attempts. Validation should be applied to all data, including query parameters, headers, and payloads.
In addition to validation, sanitize inputs to remove malicious scripts or code fragments. Use strict schemas, such as JSON Schema, to enforce validation rules across all endpoints. Consistent input validation reduces the risk of attacks and ensures data integrity.
8. Monitor and log API activity
Monitoring API traffic provides visibility into potential threats, such as unauthorized access attempts or unusual request patterns. Logging requests and responses in a centralized system streamlines incident detection and response. Logs should include essential details like timestamps, user identifiers, and IP addresses to aid forensic investigations.
Set up automated alerts for anomalies, such as sudden traffic spikes or repeated failed login attempts. Regularly review logs to identify trends and refine your security measures.
9. Restrict data exposure
APIs should minimize the amount of data they expose. Limit responses to only the fields necessary for the requested operation, and avoid including sensitive information in default responses. Use filtering and masking techniques to protect private data while maintaining functionality.
Conduct regular reviews of API responses to ensure compliance with privacy regulations and security best practices. Additionally, restrict error messages to prevent disclosing implementation details, which could provide attackers with useful information.
10. Update and patch regularly
Unpatched APIs and outdated components are common targets for attackers. Establish a process to apply security patches as soon as vulnerabilities are disclosed. Automated tools can help track and deploy patches to ensure updates are not delayed.
Test patches in a staging environment to verify compatibility and functionality before rolling them out to production. Proactively updating APIs and their dependencies reduces the risk of exploitation and ensures your systems remain secure.
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Key API security testing approaches
A strong API testing strategy is the foundation for keeping your APIs secure at every stage of their lifecycle. Here are the key approaches to consider:
Penetration testing
Manual security testing uncovers vulnerabilities that automated scanners miss, particularly business logic flaws and authorization bypasses. Penetration testers attempt to bypass authentication, exploit injection flaws, and manipulate API endpoints to assess how defenses perform under realistic attack conditions.
Regular penetration testing is especially valuable for public-facing APIs and those handling sensitive data. Test with different authentication contexts, including unauthenticated, low-privilege, and administrative access, to identify authorization gaps across user roles.
Fuzz testing
Fuzz testing pushes APIs to their limits by sending unexpected, malformed, or random inputs. The goal is to see how the API handles abnormal data without crashing, leaking information, or exposing vulnerabilities. This method is particularly effective for uncovering edge cases that traditional tests might overlook.
To get the most value from fuzz testing, focus on exposed endpoints, query parameters, and headers. Modern tools can automate this process, allowing for continuous testing to identify issues in real time and reinforce API stability.
Automated vulnerability scanning
Automated vulnerability scanning helps detect common API flaws like misconfigurations, broken authentication, and injection vulnerabilities. By integrating these tools into your development pipeline, you can catch and fix security issues early, before APIs go live.
These scans are particularly useful in dynamic environments where APIs are frequently updated. While they don't replace manual testing, they provide continuous assessments and complement other methods to create a more comprehensive security strategy.
Integrating security testing into CI/CD pipelines
Embedding these testing methods into your CI/CD pipeline ensures security becomes a natural part of your development process. Automated scans can run with each build, while periodic penetration and fuzz tests help validate your API's security before release. This proactive approach reduces vulnerabilities in production and keeps your APIs ready to face evolving threats.
Enhance your API security posture with Wiz
Traditional API security tools rely on agents or network scanners that create deployment complexity and leave visibility gaps. Wiz takes a different approach by combining API security with cloud context in a single platform.
The Wiz Dynamic Scanner uses agentless scanning across all major cloud providers to analyze every layer of your deployment. This reveals which APIs are exposed to the internet, what data they can access, and what permissions they hold. By mapping API risks alongside cloud resources, data sensitivity, and external exposure, Wiz surfaces toxic combinations that represent real attack paths, not just isolated vulnerabilities.
This context-driven approach helps teams cut through alert noise and prioritize the API risks that actually matter. Schedule a demo to see how Wiz can improve your API security posture from code to cloud.
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API Security FAQs