API Security
Protect your business-critical API interfaces against modern security threats � from broken authentication and BOLA to AI-powered attacks. Our API security consulting combines OWASP API Security Top 10 coverage, zero-trust architectures, and automated penetration testing for comprehensive protection of your data and services.
- ✓Comprehensive protection for REST, SOAP, GraphQL, and other API types
- ✓Secure authentication, authorization, and access control
- ✓Prevention of OWASP API Top 10 security risks
- ✓Comprehensive monitoring and threat detection for APIs
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Comprehensive API Security for Your Digital Transformation
Our Strengths
- In-depth expertise in modern API security and architecture
- Experienced team with comprehensive knowledge of API security frameworks and standards
- Pragmatic approach with a focus on balancing security and usability
- Proven track record in securing complex API landscapes
Expert Tip
The traditional perimeter-based security approach is insufficient for APIs. Our experience shows that the most effective API security strategy is based on a Zero Trust model that strictly authenticates and authorizes every API request regardless of its origin. Integrating API security into the entire development lifecycle (shift-left security) also demonstrably reduces the cost of remediating security issues by up to 60% compared to retroactive implementation.
ADVISORI in Numbers
11+
Years of Experience
120+
Employees
520+
Projects
Securing your API infrastructure requires a methodical, risk-focused approach. Our proven methodology ensures that your API security strategy is comprehensive, effective, and smoothly integrated into your existing processes.
Our Approach:
Phase 1: Assessment – Thorough analysis of your existing API landscape, architecture, and security controls, as well as identification of risks and vulnerabilities
Phase 2: Strategy – Development of a tailored API security strategy with clear objectives, priorities, and an aligned control framework
Phase 3: Implementation – Stepwise introduction of API security measures with a focus on critical APIs and the highest risks
Phase 4: Validation – Conducting security tests and penetration tests to verify the effectiveness of the implemented controls
Phase 5: Continuous Improvement – Establishing processes for the ongoing monitoring, assessment, and improvement of your API security
"API security is not a one-time initiative, but a continuous process. The most successful organizations treat API security as an integral part of their product lifecycle and implement security measures as early as the design phase. This leads not only to more secure APIs, but also to significantly higher development efficiency and lower overall costs."

Sarah Richter
Head of Information Security, Cyber Security
Expertise & Experience:
10+ years of experience, CISA, CISM, Lead Auditor, DORA, NIS2, BCM, Cyber and Information Security
Our Services
We offer you tailored solutions for your digital transformation
API Security Assessments
Comprehensive assessment of your existing API security posture through thorough analysis of your API landscape, architecture, controls, and practices. We identify vulnerabilities, assess risks, and provide clear recommendations for improving your API security.
- Inventory and classification of your API landscape
- Assessment of authentication and authorization mechanisms
- Analysis of API design and implementation security
- Review for OWASP API Top 10 vulnerabilities
API Gateway Security
Design, implementation, and optimization of secure API gateway solutions that serve as a central control point for your API infrastructure. Our solutions offer comprehensive security functions, performance optimization, and straightforward management.
- Secure authentication with OAuth 2.0, OpenID Connect, and API keys
- Granular access controls and permission management
- Protection against API-specific threats and attacks
- Rate limiting, quotas, and traffic management
API Penetration Testing
Specialized penetration tests for APIs, specifically designed to identify API-specific vulnerabilities and security gaps. Our experienced security experts simulate real attacks to verify the solidness of your API security.
- Manual and automated testing procedures for comprehensive coverage
- Testing for broken authentication, BOLA, and other API-specific vulnerabilities
- Security analysis of API documentation and specifications
- Detailed reports with practical remediation recommendations
API Security Monitoring & Threat Detection
Implementation of advanced monitoring and threat detection solutions specifically designed for API security. Our solutions enable early detection of attacks, unusual activities, and security incidents in your API infrastructure.
- Real-time monitoring of API traffic and usage patterns
- Anomaly detection and behavior-based analysis
- Automated responses to detected threats
- Integration into existing SIEM and SOC environments
Our Competencies in Security Architecture
Choose the area that fits your requirements
Protect your cloud environments with a holistic security strategy. Our cloud security consultants guide you through the Shared Responsibility Model, implement CSPM and CASB solutions, and ensure compliance with ISO 27001, BSI C5, DORA and NIS2 � across all cloud platforms.
DevSecOps integrates security at every stage of your CI/CD pipeline � not as a final checkpoint, but as a continuous, automated process. ADVISORI implements SAST, DAST, container security, and Security-as-Code to enable faster, more secure software releases.
Develop a future-ready Enterprise Security Architecture based on SABSA, TOGAF and Zero Trust principles. Our tailored solutions link business risks with technical security controls and provide a structured framework for the effective design, implementation and continuous improvement of your IT security — from cloud protection to meeting regulatory requirements such as DORA and NIS2.
Protect your network infrastructure with professional network security consulting: from network segmentation and Zero Trust Network Access (ZTNA) to IDS/IPS and next-generation firewalls. Our experts design tailored security architectures that meet ISO 27001, DORA, NIS2 and MaRisk requirements — delivering effective network protection in a world without traditional perimeter boundaries.
Frequently Asked Questions about API Security
What is API Security and why is it so important?
API Security encompasses all strategies, processes, and technologies for protecting application programming interfaces (APIs) against threats and misuse. As critical components of modern application architectures, APIs provide direct access to data and functions, making them particularly attractive targets for attackers.
🔐 Fundamental importance of API Security:
📈 Current trends increasing the importance:
🛡 ️ Core aspects of an effective API security strategy:
What are the most common API security threats?
APIs are exposed to specific security threats that differ from traditional web application vulnerabilities. The OWASP API Security Project identifies the most critical risks that organizations should consider when securing their APIs.
🔍 Critical API security threats according to OWASP API Top 10:
💡 Other common API security threats:
⚠ ️ API-specific attack methods:
How do you implement secure API authentication and authorization?
Secure API authentication and authorization form the foundation of an effective API security strategy. Correct implementation of these core components is essential to prevent unauthorized access and ensure the integrity of your API infrastructure.
🔐 Modern authentication standards for APIs:
🛡 ️ Best practices for solid API authorization:
⚙ ️ Implementation strategies:
🔄 Continuous improvement:
How should an API security testing program be structured?
A comprehensive API security testing program is essential for identifying and remediating security vulnerabilities early, before they can be exploited by attackers. An effective program combines various testing methods and integrates security testing throughout the entire development lifecycle.
🔄 Components of a comprehensive API security testing program:
📋 Methodical testing approaches:
🔧 Integration into the development lifecycle:
📊 Measurement and improvement:
How can I ensure the security of my GraphQL APIs?
GraphQL APIs offer unique advantages for frontend developers through their flexibility in data requests, but they also present specific security challenges. Unlike traditional REST APIs, where each endpoint returns a fixed resource type, GraphQL APIs enable complex, nested queries with potentially unlimited depth and breadth.
🔍 Specific security challenges of GraphQL APIs:
⚙ ️ Effective security measures for GraphQL APIs:
🔒 Access controls and authentication:
🛡 ️ Protection against specific attacks:
📊 Monitoring and logging:
1 query problems
🚀 Implementation strategies:
1 problems
How can API keys be managed securely?
API keys are a fundamental authentication mechanism for APIs that remains widely used despite more modern alternatives such as OAuth 2.0 and JWT. Secure management of these keys is essential to prevent unauthorized access to your API resources and to avoid data protection breaches.
🔑 Fundamentals of API key management:
128 bits)
🛡 ️ Secure storage and transmission:
⚙ ️ Implementation strategies:
📊 Monitoring and security controls:
🏢 Organizational aspects:
How can API vulnerabilities be detected through automated testing?
Automated security tests are indispensable for the continuous monitoring and improvement of API security. They enable the early identification of vulnerabilities in the development cycle and ensure that APIs remain secure even after changes. A comprehensive testing approach combines various methods for complete coverage.
🔄 Types of automated API security tests:
⚙ ️ Building an automated API security testing program:
🎯 Important test scenarios and techniques:
🔧 Best practices for effective automated tests:
📈 Measuring success and effectiveness:
What role does API security play in a Zero Trust architecture?
Zero Trust is a security paradigm based on the principle that trust is never granted implicitly but must be continuously verified. This principle is particularly relevant for APIs, which function as critical access points to enterprise data and functions. Integrating API security into a Zero Trust architecture requires a comprehensive, multi-layered approach.
🔍 Core principles of Zero Trust for APIs:
🛡 ️ Implementation strategies:
📊 Benefits of Zero Trust for API security:
What are the best practices for API authentication?
API authentication is the process of verifying the identity of a client attempting to access an API. Solid authentication is the first line of defense for your APIs. There are various methods, each with its own strengths and weaknesses.
🔑 Key authentication methods:
🛡 ️ Best practices for API authentication:
What is the difference between authentication and authorization in APIs?
Authentication (AuthN) and authorization (AuthZ) are two fundamental but distinct security concepts that are often confused. Both are essential for securing APIs, but they serve different purposes.
👤 Authentication (Who are you?):
🔑 Authorization (What are you allowed to do?):
* client has.
🔄 Interaction:
* authorization. It is necessary to know *who
* the client is before deciding *what
* they are allowed to do.
💡 Why the distinction matters:
How do I protect my APIs against injection attacks?
Injection attacks are among the most common and dangerous vulnerabilities for web applications and APIs. They occur when untrusted data is sent to an interpreter as part of a command or query. The goal is to trick the interpreter into executing unintended commands or granting unauthorized access to data.
💉 Types of injection attacks on APIs:
🛡 ️ Protective measures against injection attacks:
What are the OWASP API Security Top 10 and why are they important?
The OWASP (Open Web Application Security Project) API Security Top
10 is a list of the most critical security risks for APIs, compiled by security experts worldwide. It serves as a standard awareness document for developers, architects, security teams, and organizations to understand and avoid the most common and serious API vulnerabilities.
🎯 The OWASP API Security Top
10 (Version 2023):
2023
2023
2023
2023
2023
2023
2023
2023
2023
2023
💡 Why are the OWASP API Security Top
10 important?
10 is an essential step toward developing and operating secure APIs in the modern digital landscape.
How does rate limiting work and why is it important for APIs?
Rate limiting is a technique for controlling the frequency with which a client (user, application, IP address) may call an API within a defined time period. It is a critical security and stability measure for APIs.
⏱ ️ How rate limiting works:
429 Too Many Requests`.
🛡 ️ Why is rate limiting important?
⚙ ️ Implementation strategies and algorithms:
📊 Best practices for rate limiting:
What is an API gateway and what security functions does it provide?
An API gateway is a management component that serves as a central entry point (single point of entry) for all or a group of API requests from external or internal clients. It acts as a reverse proxy that receives, processes, and forwards requests to the appropriate backend services. API gateways play a critical role in securing, managing, and scaling APIs.
🚪 How it works:
🛡 ️ Key security functions of an API gateway:
10 risks (SQLi, XSS, etc.).
✨ Additional benefits of an API gateway (beyond security):
How do I secure APIs in a microservices architecture?
Securing APIs in a microservices architecture presents particular challenges, as the attack surface is larger and communication becomes more complex (both north-south and east-west traffic). A multi-layered approach is required.
🧭 Challenges:
🛡 ️ Security strategies for microservices APIs:
* microservices:
*
* Enforces encrypted and mutually authenticated connections between all services. Prevents eavesdropping and spoofing within the internal network.
*
* Defines which services are allowed to communicate with each other (e.g., Service A may call Service B, but not Service C).
*
* Implements Zero Trust principles at the network level.
What is API schema validation and how does it help with security?
API schema validation is the process of verifying whether incoming API requests and outgoing API responses conform to a predefined structure (schema). This schema describes the expected data format, data types, required fields, length restrictions, and other rules for API usage. It is a fundamental security practice.
📜 What does an API schema define?
⚙ ️ How does validation work?
*
* For RESTful APIs (version 2.0 was called Swagger).
*
* A general standard for describing JSON data structures, often used within OpenAPI.
*
* For GraphQL APIs.
*
* For XML-based APIs (e.g., SOAP).
*
* The request/response conforms to the schema and can be processed further.
*
* The request/response deviates from the schema and is rejected (typically with a `
400 Bad Request` for requests or an internal error for responses).
🛡 ️ How does schema validation help with security?
💡 Implementation:
What is the difference between API security and web application security?
Although API security and web application security are closely related and often overlap, there are important differences in focus and in the specific threats involved.
🌐 Web Application Security (Traditional):
🛡 ️ API Security:
🔄 Overlaps and differences:
10 2023) are particularly critical, as attackers often attempt to directly access data or functions for which they have no permission by manipulating IDs or parameters.
💡 Conclusion:API security is a specialized discipline within the broader field of application security. While many fundamental security principles apply, the specific nature and usage patterns of APIs require a particular focus on authentication, authorization at various levels, rate limiting, and securing the programmatic interface itself. A modern security strategy must comprehensively address both aspects – web application security and API security.
How can I protect sensitive data in API responses?
APIs often return data, some of which may be sensitive (e.g., personally identifiable information – PII, financial data, health data). It is essential to adequately protect this data in API responses to avoid data protection breaches and compliance violations.
🔒 Strategies for protecting sensitive data in API responses:
10 2023).
**** ****
**** 1234` for a credit card number, `***@example.com` for an email address).
* protect the data itself if the response is intercepted or compromised on the client. It is a necessary but not sufficient measure.
What are "shadow APIs" and "zombie APIs" and how do I find them?
Shadow APIs and zombie APIs are terms describing undocumented, forgotten, or no longer managed APIs that are still active and reachable. They represent a significant security risk, as they often do not meet current security standards, are not monitored, and provide an unnoticed attack surface (see API9:
2023 – Improper Inventory Management of the OWASP Top 10).
👻 Shadow APIs:
🧟 Zombie APIs:
🔍 How do I find and manage shadow/zombie APIs?
What security considerations are there for GraphQL APIs compared to REST APIs?
Although many fundamental security principles apply to both GraphQL and REST APIs (authentication, authorization, input validation, rate limiting, HTTPS), the different architecture and operation of GraphQL give rise to specific security considerations.
🌐 REST API – Security considerations (typical):
10 for web applications/APIs are directly applicable.
🚀 GraphQL API – Specific security considerations:
*
* Must be more complex than simply counting the number of requests. The *complexity
* of the query must be taken into account (query cost analysis).
*
* Traditional endpoint-based WAF rules are less effective.
*
* Complex queries can overload the server (CPU, memory, database). Protective measures such as query depth limits, complexity analysis (query cost), timeouts, and pagination are essential.
*
* Clients can bundle many operations into a single request.
*
* The schema clearly defines the available data and operations, which facilitates validation.
*
* By default, GraphQL allows schema introspection. Attackers can use this to explore the entire API structure and find vulnerabilities. Introspection should be disabled or restricted in production environments.
200 OK` status even when errors have occurred. Error details are returned in the `errors` array of the JSON response. It is important not to expose sensitive information (stack traces, etc.) in error messages.
💡 Summary of differences in focus:
*
* Focus on resource/endpoint security, HTTP method permissions.
*
* Focus on query complexity, schema security (introspection), fine-grained field authorization, and protection against resource exhaustion through flexible queries.Both API types require careful security planning, but GraphQL requires additional, specific controls to address the challenges of its flexible nature.
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