API Security Tutorial

What is API Security?

In 2024, API security remains a critical concern for organizations relying on interconnected digital systems. A recent survey revealed that 84% of enterprises experienced at least one API-related security incident in the past year, highlighting the pressing need for robust protective measures. ​

Effective API security focuses on safeguarding the integrity, confidentiality, and availability of APIs. This is achieved through implementing authentication, authorization, encryption, and continuous monitoring protocols to ensure that only authorized users and applications can access these interfaces.​

As the number of APIs continues to grow, organizations must prioritize comprehensive security strategies to mitigate potential vulnerabilities and protect sensitive data.

Looking ahead, the explosive growth of APIs is creating substantial management challenges. According to IDC Insights,

“By 2026, less than 40% of enterprise APIs will be managed, as explosive API growth outstrips the capacity of traditional management tools.”

In summary, API security is a multi-layered discipline that addresses various vulnerabilities to provide comprehensive protection in an increasingly interconnected world.

API Security vs APP Security

Security teams are stretched thin despite requiring more resources than ever. Companies are paying for expensive API security solutions yet applying endless amounts of duct tape and super glue to make them work while finding workarounds for everywhere they can’t work. And despite all this effort, the frequency, severity, and damage of API attacks keeps getting worse. Little wonder, then, that there’s been a strong push to reunite application security and API security under one umbrella.

On one front, that push is coming from legacy WAF vendors. Big names in this space have recently acquired API security vendors and begun to talk about WAF and API as two sides of the same application security coin. There has not been the same effort from the startups in the API security space to add WAFs to the product line — perhaps because they have a vested interest in maintaining a separate dichotomy.

On another front, Gartner put its weight behind the concept of integrating WAF and API security. It used to have a Magic Quadrant dedicated to WAF vendors (it never had one dedicated to API security vendors), but several years ago it updated that quadrant to encompass Web Application and API Protection (WAAP).

Few know the tech landscape as well as Gartner, so for them to draw an explicit link between web application and API security speaks loudly about how these tools function together and where the vendor landscape is headed — integrated not independent.

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API Discovery

At its core, API discovery involves identifying, cataloging, and documenting all APIs within an organization, both internal and external. This process is essential for maintaining a secure and efficient API environment. Automated API management platforms can assist in this endeavor by continuously scanning and mapping the API landscape, ensuring that all APIs are accounted for and properly managed.

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"....60% of enterprises will lag in their digital transformation initiatives due to the lack of API discovery capabilities...”

- Gartner

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In a large organization, it's impractical for anyone to keep track of every API and the data each one exposes. It isn't surprising that there is the problem of shadow APIs (similar to shadow IT), API endpoints that exist within an organization's environment but are not known or managed by the organization's IT/DevSecOps teams.

The challenge of maintaining an API inventory intensifies when considering projections that by 2025, fewer than half of the APIs will be actively managed.

Finally, APIs go through their lifecycle. As an API evolves, new versions of an API come up, or an API may even be deprecated but continue to operate temporarily for backward compatibility and then be forgotten or gradually fall off the radar because they receive very little traffic.

API discovery is a race between API providers and hackers; the latter can easily exploit APIs once discovered! To identify your APIs before an attacker does, you must first analyze your API traffic from across different sources. This data is sourced from API gateways, load balancers, Linux kernel (eBPF), or directly from network traffic. It's then processed by a specialized engine that produces a comprehensive list of APIs.

This list can subsequently be compared with the catalogs of APIs available through an API management layer.

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Real-time API Protection

‍75% of enterprises experiencing API-related security incidents due to inadequate real-time safeguards.

- Outshift by Cisco

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Real-time API protection is crucial for defending APIs against swiftly changing cyber threats. This preventative strategy includes ongoing monitoring, threat identification, and prompt reaction to vulnerabilities and attacks. Real-time API protection utilizes cutting-edge technologies such as machine learning and behavioral analytics to detect anomalies and potential threats as they emerge.

By persistently examining API traffic and patterns, these systems can identify and counteract issues like unauthorized access, data breaches, and denial-of-service attacks instantaneously.

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AI-enabled API Protection

With the arrival of GenAI tools such as ChatGPT, Gemini, and Dall-E, the global API ecosystem was forced to adapt to the artificial intelligence era. AI systems use APIs for a wide range of processes, including linking AI models with the data streaming platform or service it needs to access.

By creating a cohesive ecosystem that employs data streaming with highly efficient AI/Machine Learning/LLM models, humans have managed to scale systems and services that are continuously improving living conditions and business output.

While the oldest tricks in the book (like Broken User Authentication, Phishing, DDoS, and SQL Injections) continue to claim the top spots, organizations also have to protect themselves from brute force attacks like Cross-site Scripting (XSS) and credential stuffing attempts. And in more recent years, AI, Machine Learning (ML) and LLM tools have found their way into cyberattacks. As a result, the frequency of API-based attacks on corporations and businesses has escalated significantly.

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“...1 out of 4 companies faced a cyber attack in the first few months of 2024..”

- Check Point Research

AI-powered pattern recognition systems can detect irregular activity across API surfaces, while data analytics has the capability to analyze long-term patterns to detect Common Vulnerabilities and Exposures (CVEs) that may be exploited later on.

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Threat Discovery

From data gathering to anomaly detection, AI algorithms meticulously analyze patterns and user behavior to establish standard baselines for API activity. Through constant monitoring of API traffic, InfoSec teams can swiftly pinpoint deviations from these established norms, enhancing security measures effectively.

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Predictive Analytics

AI excels at empowering organizations with the ability to anticipate and preemptively tackle imminent security threats. Leveraging historical data and pattern recognition, AI forecasts potential vulnerability areas, enabling security teams to proactively mitigate risks before they're exploited by cybercriminals.

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Real-time Response & Remediation

Upon detecting an API threat, AI can swiftly enact actions like blocking suspicious traffic, alerting security teams, or temporarily restricting access to shield the API from additional harm. This instantaneous response is vital for threat mitigation and damage reduction.

Behavioral Biometrics

AI can enhance API security through the integration of behavioral biometric, which identifies users by analyzing their distinct behavioral traits, which could include typing speed, mouse movements, and even navigation habits. Continuously monitoring these patterns enables AI to swiftly detect deviations, indicating possible account compromise, account takeover (ATO) or fraudulent behavior.

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The Competitive Advantage of AI in API Security is Unparalleled as it propels API Security to the forefront of the Industry.

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API Security Leaks

API Leaks refer to the accidental or intentional exposure of sensitive data through Application Programming Interfaces (APIs). If not secured properly, APIs can expose sensitive information, such as personal data, financial information, or other types of confidential data, to unintended parties. API leaks can occur due to misconfigured API settings, vulnerabilities in the code of the API, or inadequate security protocols. These leaks can lead to severe consequences, including data breaches, identity theft, and financial loss.

There are several types of API leaks, including:

1. Data leaks: These are the most common type of API leaks, where sensitive data such as personal information, passwords, and financial data are made accessible through APIs.
2. Access leaks: In this type of leak, unauthorized users are granted access to restricted APIs, giving them access to sensitive data that they should not have access to
3. Integration leaks: This type of leak can occur when APIs are integrated with other applications without proper security measures in place
4. Supply chain leaks: These leaks occur when third-party APIs with vulnerabilities are included in the supply chain, giving attackers a means to exploit the weak points in the API
5. Configuration leaks: This type of leak happens due to misconfigured APIs, where settings are not set to the desired level of security, making data vulnerable to attacks.

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API Security OWASP TOP 10 Vulnerabilities

• API1:2023 (Broken Object Level Authorization): To address BOLA, detect vulnerabilities in both development and production, and consider using an inline API security tool to block attacks, especially when immediate code fixes are challenging. Risk Rating: 6.0

• API2:2023 (Broken Authentication): Start with detective controls to catch and block attacks, assess API vulnerabilities, prioritize high-risk ones, and work on fixes. If you don't control the app, collaborate with vendors with evidence and priorities. Risk Rating: 8.0

• API3:2023 (Broken Object Property Level Authorization): Identify vulnerable API endpoints, instruct developers to fix issues, and report third-party vulnerabilities. An inline API security tool can provide protection when quick fixes aren't feasible. Risk Rating: 5.3

• API4:2023 (Unrestricted Resource Consumption): Create a threat model for resource consumption, set external limits, and make risk mitigation decisions even without direct control over application code. Risk Rating: 8.0

• API5:2023 (Broken Function Level Authorization): Restrict function access in the code, maintain good API hygiene, and consider monitoring and blocking tools for better mitigation. Risk Rating: 8.0

• API6:2023 (Unrestricted Access to Sensitive Business Flows): Understand your business flows, use automated tools sparingly, employ blunt-force approaches, and maintain good API governance. Risk Rating: 5.3

• API7:2023 (Server Side Request Forgery): Ideally, restrict at the resource-fetching mechanism. If not, apply controls at the network or application layer, or use a dedicated tool to block SSRF attacks. Risk Rating: 5.3

• API8:2023 (Security Misconfiguration): Implement good security governance, create API specifications, and prioritize where to apply resources to eliminate misconfigurations. Risk Rating: 9.0

• API9:2023 (Improper Inventory Management): Begin with API discovery for better documentation, build API specifications into your development process, and request them from vendors to manage inventory properly. Risk Rating: 5.3

• API10:2023 (Unsafe Consumption of APIs): For APIs you control, implement best practices and evaluate against a checklist. For third-party APIs, validate their compliance with your checklist and establish a response plan for non-compliance. Risk Rating: 7.0

• Injection (formerly API8:2019): Injection attacks remain the most dangerous threat for APIs. Be especially aware of their risk and take proactive measures to prevent them. Risk Rating: 9.0

Top Open Source API Testing Tools

In 2025, as APIs continue to dominate application architectures, testing tools play a vital role in ensuring robust security and performance. Open source API testing tools help teams automate functional, load, and security tests, and identify issues early in the development pipeline. Below are some of the top open source tools actively used by security and QA teams today:

GoTestWAF

GoTestWAF by Wallarm is a powerful open-source tool for testing both traditional Web Application Firewalls (WAFs) and modern API protection solutions. It simulates real-world attacks and validates whether your API security mechanisms detect and block malicious traffic.

Key features:

• Built-in test suites for OWASP Top 10, API Top 10, and common attack vectors
  
  
• Supports SOAP, REST, GraphQL, gRPC, XMLRPC and WebSocket APIs
  
  
• Custom payloads and scenarios to simulate complex attack chains
  
  
• CI/CD-ready for automated security testing in pipelines
  
  
• Real-time dashboards and JSON reports for integration with external systems
  

Postman

Postman remains a staple for API development and testing. While traditionally used for functional validation, it also supports basic security testing and automation.

Key features:

• Automated API test suites and test scripting with JavaScript
  
  
• CI/CD integrations via Newman CLI
  
  
• Environment and variable management for staging vs. production
  
  
• Response time monitoring and performance insights
  
  
• Supports REST, SOAP, and GraphQL APIs
  

Swagger (OpenAPI)

Swagger (now part of the OpenAPI Initiative) continues to help teams design and document APIs. It enables testing through code generation and mock servers.

Key features:

• Top-down and bottom-up API design options
  
  
• Auto-generates documentation and SDKs
  
  
• Integrates with testing tools to simulate and validate endpoints
  
  
• OpenAPI 3.1 support with improved schema capabilities
  
  
• Rich ecosystem of tools like Swagger Editor and Swagger UI
  

JMeter

Apache JMeter has evolved beyond just load testing and can now be adapted for API security testing with custom scripts and plugins.

Key features:

• Load testing of REST, SOAP, and GraphQL APIs
  
  
• Parameterized testing with CSV or JSON inputs
  
  
• Integration with Jenkins, GitHub Actions, and other CI systems
  
  
• Scripting via JSR223 (Groovy, Java) for advanced validation
  
  
• Real-time performance metrics and visualization
  

SoapUI

SoapUI, both in its open-source and pro versions, is widely used for testing web services, including APIs used in enterprise systems.

Key features:

• Supports REST, SOAP, GraphQL, and JMS APIs
  
  
• Drag-and-drop interface for test creation
  
  
• Assertions for security and functional validation
  
  
• Reusable test cases across environments
  
  
• Pro version includes advanced reporting and data-driven testing
  

Karate

Karate DSL combines API test automation, performance testing, and mocking in a single framework using BDD-style syntax.

Key features:

• Write tests in Gherkin syntax with no Java code required
  
  
• Parallel test execution and performance testing built-in
  
  
• Mock server capabilities to simulate upstream/downstream services
  
  
• CI/CD integrations and report generation
  
  
• Native support for JSON, XML, and GraphQL
  

Fiddler Everywhere

Fiddler remains relevant as a network proxy and debugging tool with enhanced API testing capabilities.

Key features:

• Inspect and replay HTTP/HTTPS traffic from any client
  
  
• Modify headers, cookies, and payloads to simulate edge cases
  
  
• Support for scripting and custom rules
  
  
• Cross-platform support for Windows, macOS, and Linux
  
  
• Collaboration features for teams to share sessions and test scenarios

API Security Best Practices - Top-15 Standards:

We talked to many product security experts about where they think everyone should begin their API security program. Here is what they said.

1. Inventory all APIs 

Security and engineering leaders should easily answer key questions: How many APIs are in use and where is sensitive data transferred? In 99% they can’t. It's crucial to have an up-to-date inventory of API methods and which of them handle PII and PHI data. While specialized products exist, open-source solutions like APIClarity can also aid in API discovery.

2. Discovery deprecated (Zombie) and undocumented (Shadow) APIs

Zombie, Shadow, and Orphan APIs pose an enormous risk (see 2023 State of the API Report). Proper API Governance includes the process for producing and managing specifications in Dev, as well as identifying noncompliance with specs. OSS tool APIClary can help here, too. 

3. Deploy API gateways

Utilize API gateways for managing, monitoring, and securing API traffic (note: a lot of APIs are actually unmanaged!). This adds an essential API security layer with capabilities like Rate Limiting, Caching, Authentication, Access Control, and CORS. A lot of powerful gateways are open-sourced and have premium options including Kong API Gateway and Tyk.

4. Automate API security testing

It’s always better to discover dangerous security misconfiguration and other issues in dev environment vs in production. While not exhaustive, open-source tools like ZAP, openapi-fuzzer, and RESTler provide significant value. There is not best recipe but most companies have a combination of DAST, SAST, and IAST and devtools to help developers develop secure code (such as plugins for IDEs)

5. Proactively look for API Leaks

API secrets leakage can lead to serious incidents. Regularly scan for exposed credentials, including API keys, in GitHub repositories, Postman collections, and similar platforms to prevent unauthorized access. Code repositories are often spots where engineers accidentally leak API keys. Find leaked credentials with tools like TruffleHog.

6. Risk score APIs to prioritize security efforts

Don’t be overwhelmed by the number of APIs to secure. Once APIs are identified, you can prioritized testing and audit based on risk factors suitable for your specific case. Consider aspects like data sensitivity (endpoints handling PII data such as names or SSN), exposure level (external vs. internal API), and the number of parameters.

7. Audit existing tools to make sure they support APIs

Many security tools you trusted for years, including scanners and WAFs, may not fully protect your app estate emerging API threats. Moreover, often they don't provide protection for your API stack at all - for example, they may not analyze traffic in GraphQL or gRPC. Test your tools' protocol support using open-source projects like GoTestWAF (read guide) or use our online service - API Security testing platform.

8. Comply with the OWASP Top-10 API Security Recommendations

The best place to get familiar with API threats is the OWASP API Security Top-10, or the summary we prepared for you (see the relevant section here). This list is a must-read for both security and eng teams and provides an extensive examination of significant API vulnerabilities and mitigation techniques.

9. Extend Beyond OWASP

Wallarm publishes quarterly and annual API ThreatStats reports covering emerging API threats, drawing from an analysis of all known CVEs and billions of observed attacks. Consider this a dynamic and up-to-date complement to the OWASP API Security Top-10

10. Use only industry-standard methods for authentication and authorization

Do not reinvent AuthN/AuthZ methods.  Rely only on OAuth 2.0, JWT, OpenID Connect, and Bearer Tokens, or other industry standards for your authentication. Couple with stringent authorization checks at each API endpoint for access control. Even minor oversights in authorization have led to catastrophic data breaches in APIs over the past few years. 

11. Find APIs which can be abused and get ready

APIs are developed to be consumed by software and hence inherently prone to abuse. Figure out which APIs are likely to be abused and prepare a plan of action. Rate limiting and throttling are effective but not sufficient against advanced abuses. For such cases, building protection at the application level or employing specialized products is necessary.

12. Use encryption for external and internal microservices

In a zero-trust environment, using mTLS between microservices is a best practice.

13. Actively enforce API policies on traffic

Thoroughly validate and sanitize all user inputs to avert typical vulnerabilities such as SQL injection, SSRF, and other forms of injection attacks. A proven strategy is to validate all API calls against their specs to screen out potentially harmful requests. An effective tool for this is the open-source API firewall, which functions as a reverse proxy, validating API requests and responses based on OpenAPI and GraphQL schemas.

14. Implement API logging

Maintain API logs and implement real-time monitoring to detect and respond to abnormal actions (including on the session level). This can all help to isolate ongoing incidents swiftly.

15. Pay Attention to LowCode & NoCode Tools

Be aware of the implications of LowCode and NoCode tools, especially those with direct data access, as their security aspects are often overlooked. Most of them are using APIs for integrations.

‍‍API Authentication Methods

The task of verifying users’ identity is imperative as it keeps ill-usage of API at bay and verifies user authenticity before granting him the access to the stored information kept for better Web API Security. It involves verifying the identity of someone who tries to view or edit the API resources, allowing only authenticated users for the same.

1. Host-based authentication

The host-based authentication schema is widely used for IOT devices and raw network authentication. It is not recommended for web technologies since it can be bypassed with spoofing. This process comprises verifying the host or server so that only the verified users can access resources deployed on the servers. It doesn’t demand any key or other means to initiate the process. However, the server should be competent to validate the login keys beforehand to keep the incidents of DNS spoofing, routing spoofing, and IP spoofing under control. 

In the process and manner, it’s very much similar to RSA. 

The argument used here is either yes or no. By default, no argument is set. The host-based verification of users can be done by an administrator by creating a private key for the local host or extracting the public key used for the localhost. 

2. Basic authentication

One of the most straightforward API identity-confirmation schemes, this method is crafted using HTTP protocol and process as the client dispatches an HTTP request with a pre-built header for verification of authenticity and demanding credentials like account’s password and username. This basic check is done in a browser-powered environment.

Being supported by every possible browser and server makes basic identity-confirmation the most common one. The credential details are shared over the network in the form of cleartext and are encoded using base64. The credential details are shared over the network in the form of cleartext (or base64) by default, this is a bad practice since it gives man-in-the-middle attack vectors. The good practice is to encrypt the credentials using algorithms such as RSA, SHA-256 or even custom made ones.

It is functional over proxy servers and grants access to resources not hosted on IIS servers. As it fails to add encryption, not much security can be expected out of it. Also, it’s more prone to replay attacks.

3. OAuth

OAuth is the open method of identity confirmation. It is a customary API authenticity-verification technique that covers users’ identity verification and defining authorization criteria. The protocol is used widely for allowing applications to authorize their users based on tokens, published from OAuth server (such as Google).

It requires asking for a token when someone tries logging into the system. The token serves here as the means of verifying and approving the user identity. The person/request-creator has to forward the request to accessing the resource to the authentication server. Based on the quality and result of identity-verification, the server can accept or reject the request. 

OAuth is safer and more secure than other processes making it the first choice for many. The three key ingredients of OAuth are OAuth provider, Google and Facebook are the common ones, OAuth Client, refers to the information-owning website/page, and owner, denotes the user making an access request.

4. OAuth 2.0

A widely used protocol of API access management, OAuth 2.0 is an updated version of OAuth. Its functioning involves keeping the API client access limited by using HTTP services for the client application enabling. Some HTTP services needed for this sort of protocolare GitHub and Facebook. It takes the help of a code for identity-verification and doesn’t ask for user credentials.

The three factors involved in OAuth 2.0 are the user, who is possessing the data to which the API wants the view or edit permission, the application, and the API.

Using this method for identity confirmation, it’s easy to interpret user data using different resources. It can be deployed for the verification and approval of web-based, mobile-based, and desktop-based applications/devices.  

5. SAML

SAML stands for Security Assertion Markup Language and is a standard API process for identity confirmation using single-sign-on technology. It denotes confirming the user as per the provided details. Once the process completes and the user is verified, access to assorted applications/resources is granted. Presently, its SAML 20 version is running. It’s very much similar to the ID. Only user identity assessment is done with its help.

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What Does API Security Entail? 

APIs, related to the app that you own, can only be controlled. This is why security API is focused on securing APIs that are exposed to a user, directly or indirectly. APIs, offered by other parties, that a user consumes are not a prime priority of Web API security as valuable insights related to such APIs can be gained by detailed analysis of outgoing API traffic. 

One another key point to note here is that API security practice implementation involves multiple teams and systems. Network security principles like throttling, rate limiting, along with key data security concepts like identity-based security and analytics are a part of API security.

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API Protocols

Based on the requirements, APIs can be used in various forms and styles. The chosen API style (REST, SOAP, GraphQL, gRPC, Websocket or Webhooks) decides how API security should be applied and implemented.  Different API protocols, such as gRPC, GraphQL, and others, introduce their own unique security threats and attack vectors. For instance, GraphQL, due to its flexible querying capability, can be prone to resource exhaustion attacks if queries aren't properly validated and rate-limited. Each protocol, with its distinct architectural and operational nuances, requires specialized security considerations to address potential vulnerabilities and defend against tailored exploitation techniques.

Comparing REST, SOAP, and GraphQL API Security

Modern APIs primarily follow one of two architectural styles:

• SOAP – A structured messaging protocol that supports multiple transport layers.
• REST – A lightweight framework that operates over HTTP/S and commonly exchanges data in JSON format.

Both SOAP and REST utilize HTTP requests and Secure Sockets Layer (SSL) for encryption, but their security models differ significantly.

SOAP API Security

• SOAP includes built-in security extensions designed to enhance protection.
• It adheres to security standards set by W3C and OASIS, such as SAML authentication, XML encryption, and digital signatures.
• It supports Web Services Security (WS-Security), enabling strong enterprise-grade protection for web services.
• SOAP’s error-handling capabilities are reinforced through WS-ReliableMessaging, ensuring message integrity.

REST API Security

• REST does not inherently provide security mechanisms—protection must be implemented in the API’s design.
• Security considerations include data encryption, secure deployment, and client-server interaction safeguards.
• Unlike SOAP, REST lacks built-in mechanisms for error recovery and requires data to be resent when failures occur.
• A common security strategy involves deploying REST APIs behind an API gateway, which acts as an intermediary to enforce security policies and mitigate threats.

Summary: SOAP inherently integrates robust security measures, whereas REST APIs require additional security layers depending on their implementation.

Securing GraphQL APIs

GraphQL is a query language that enables clients to request specific data from an API in a structured format. Unlike traditional REST or SOAP approaches, GraphQL allows clients to define and retrieve exactly the information they need from one or multiple sources.

Since GraphQL permits highly complex queries, servers must be equipped to handle potential abuse. Without proper safeguards, excessive or malicious requests can overload the server, leading to performance issues or downtime.

Key Strategies for GraphQL Security

• Query Timeouts – Setting a maximum execution time for each request prevents long-running queries from overwhelming system resources.
• Depth Limitation – Restricting the depth of queries ensures that clients cannot exploit deeply nested structures to generate excessive computational loads.
• Complexity Scoring – Assigning a complexity score to API requests based on processing demands helps restrict expensive operations that exceed a defined threshold.
• Rate Limiting – Limiting the frequency of requests prevents repeated medium-sized queries from consuming too many server resources, ensuring balanced usage.

By implementing these measures, GraphQL APIs can be fortified against attacks and optimized for performance, minimizing risks associated with excessive or malicious queries.

API Protocol Comparison

How To Secure API ?

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Our seasoned API security team is skilled enough to secure APIs in any sort of environment. We have mastered the art and science of API security in AWS, GCP, Azure and IBM Cloud ecosystem, regardless of the type of deployment.