Securing Application Programming Interfaces (APIs) is critical for modern digital businesses, as APIs serve as the communication backbone for applications, microservices, and connected devices. A comprehensive strategy involves security from the initial design phase through continuous management and monitoring. 

Secure API design principles

• Implement strong authentication and authorization:
  • Authentication verifies the identity of the user or service accessing the API. Modern, token-based standards like OAuth 2.0 are recommended for this purpose.
  • Authorization determines what a verified user or service is permitted to do. Use fine-grained controls such as Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC) to apply the principle of least privilege.
• Use an API Gateway: Place all API endpoints behind an API Gateway to act as a centralized control point. It provides a single entry point for applying security policies, managing traffic, and handling authentication.
• Encrypt all communications: Enforce HTTPS with strong Transport Layer Security (TLS) versions (1.2 or higher) to encrypt data in transit. For sensitive internal communications, consider using Mutual TLS (mTLS) to ensure both the client and server are mutually authenticated.
• Validate all input and output:
• Input validation checks that all data sent to the API is valid and conforms to expected formats and constraints. This helps prevent common attacks like SQL injection and cross-site scripting (XSS).
• Output sanitization and filtering should ensure that APIs never expose more data than necessary.
• Implement rate limiting and throttling: Rate limiting restricts the number of requests a user can make over a specific period, protecting APIs from abuse and denial-of-service (DoS) attacks. Throttling can be used to manage traffic spikes and ensure fair resource distribution.
• Avoid sensitive data in URLs and payloads: Never include credentials or sensitive data in API endpoint URLs, as these can be captured in server logs and browser history. If sensitive data must be in the payload, use JSON Web Encryption (JWE) for confidentiality.
• Follow the Zero Trust model: Operate on the principle of "never trust, always verify." Every request, whether from inside or outside the network, must be authenticated and authorized.