API security protects application programming interfaces from unauthorised access, data theft, and malicious abuse. Well-designed API security enables secure resource sharing whilst preventing unauthorised access and exploitation.
API Authentication
API Keys - simple credentials identifying applications accessing APIs. API keys should be treated as secrets, transmitted only over HTTPS. Keys enable basic access control and rate limiting per key.
OAuth 2.0 - secure delegation enabling users granting applications API access without sharing passwords. OAuth is industry standard for third-party API access.
Mutual TLS (mTLS) - both client and server authenticate using certificates, providing stronger authentication than simple API keys. mTLS is common for service-to-service APIs.
JWT Tokens - stateless authentication where tokens contain signed user information. Tokens enable scalable authentication without server-side session storage.
API Authorisation
API authentication verifies identity; authorisation determines what authenticated users can access. Role-based access control (RBAC) and attribute-based access control (ABAC) enforce fine-grained permissions.
Principle of least privilege grants minimum necessary access, reducing damage potential if credentials are compromised.
Rate Limiting
Rate limiting restricts request frequency per user or IP address, preventing brute force attacks and denial-of-service (DoS) attacks.
Tiered rate limits provide different limits for different user types (free, paid, enterprise), protecting infrastructure from excessive free tier usage.
Input Validation
All API inputs must be rigorously validated:
- Type validation ensuring inputs match expected types
- Length validation preventing buffer overflows and resource exhaustion
- Format validation ensuring inputs match expected patterns
- Whitelist validation accepting only known-good inputs
Injection attacks exploiting inadequate validation can enable unauthorised database access or code execution.
Output Encoding
API responses should be properly encoded preventing injection attacks through response data.
JSON responses should avoid embedding user data directly without encoding, preventing stored XSS attacks.
HTTPS and TLS
All API communications must use HTTPS/TLS encrypting data in transit. APIs exposing unencrypted data are vulnerable to man-in-the-middle attacks and interception.
Versioning and Deprecation
API versioning enables introducing changes without breaking existing integrations. Old API versions should be deprecated with appropriate notice periods.
Breaking changes should be announced in advance enabling client migration to newer versions.
Error Handling
APIs should avoid exposing sensitive information in error messages. Generic error messages hide implementation details preventing information disclosure attacks.
Detailed error logging on servers aids debugging without exposing information to clients.
PixelForce API Security
PixelForce's development of marketplace platforms, health applications, and enterprise solutions involves securing APIs managing sensitive business and personal data. Rigorous API security is integrated throughout our development process.
API Rate Limiting
Implementing rate limiting protects APIs from:
- Brute force attacks attempting password guessing
- Bot attacks overwhelming infrastructure
- Denial-of-service attacks disrupting service availability
Communicating rate limits to clients enables proper usage planning.
API Monitoring and Logging
Comprehensive logging tracks API access, modifications, and security events. Monitoring identifies suspicious patterns including:
- Unusual access patterns
- Rate limit violations
- Authentication failures
- Anomalous data access
CORS (Cross-Origin Resource Sharing)
CORS policies control which origins can access APIs from browsers. Restrictive CORS policies prevent unauthorised cross-site access.
Wildcards (allowing all origins) should be avoided, limiting CORS to trusted origins.
API Documentation Security
Documentation should not expose sensitive implementation details enabling attackers to identify vulnerabilities. Security considerations should be documented without revealing specific protections.
GraphQL Security
GraphQL APIs require additional consideration:
- Query complexity analysis preventing computationally expensive queries
- Depth limiting preventing deeply nested query exploitation
- Rate limiting per user and per query
- Proper error handling not exposing schema details
Webhook Security
APIs calling webhooks should:
- Verify webhook endpoint URLs are under client control
- Sign webhook requests enabling client verification of source
- Limit webhook payload sizes preventing resource exhaustion
- Implement webhook retries with exponential backoff
API Security Testing
Regular security testing including:
- Penetration testing identifying vulnerabilities
- Fuzzing testing random invalid inputs
- Authentication and authorisation testing
- Rate limiting testing
Certificate Pinning
Clients implementing certificate pinning validate specific server certificates, preventing man-in-the-middle attacks even if certificate authorities are compromised.
API Gateway Security
API gateways provide centralised security including:
- Authentication and authorisation
- Rate limiting and throttling
- Input validation
- Request/response logging
Third-Party API Integration
Organisations using third-party APIs should:
- Verify provider implements security best practices
- Understand data handling practices
- Review provider security credentials and certifications
- Monitor API usage for anomalies
API Key Rotation
API keys should be rotated periodically, and compromised keys should be invalidated immediately. Graceful key transition periods enable client migration.
OWASP API Security Top 10
The OWASP API Security Project identifies top 10 API vulnerabilities:
- Broken Object-Level Authorisation
- Broken User Authentication
- Excessive Data Exposure
- Lack of Resource & Rate Limiting
- Broken Function Level Authorisation
- Mass Assignment
- Security Misconfiguration
- Injection Attacks
- Improper Asset Management
- Insufficient Logging & Monitoring
Future API Security Trends
Zero-trust architecture requires continuous authentication and authorisation for all API access rather than perimeter-based security.
GraphQL-specific security standards and best practices are emerging as GraphQL adoption increases.