What are the most important API security best practices?

The core practices are: strong authentication (OAuth 2.0 or API keys with rotation), proper authorisation (users only access their own data), rate limiting to prevent abuse, input validation to reject malicious requests, encrypted transport (TLS everywhere), and monitoring for anomalous behaviour.

What is the OWASP API Security Top 10?

The OWASP API Security Top 10 is a list of the most critical API security risks: broken object-level authorisation, broken authentication, excessive data exposure, lack of rate limiting, broken function-level authorisation, mass assignment, security misconfiguration, injection, improper asset management, and insufficient logging.

How do I test API security?

API security testing combines automated scanning with manual testing — probing authentication flows, testing authorisation boundaries (can user A access user B's data?), checking input handling, and verifying that error responses do not expose internal details. Testing should be done in a controlled environment.

AI Security

API Security Best Practices

The six core API security practices are: strong authentication, proper authorisation, rate limiting, input validation, encrypted transport, and monitoring for anomalous behaviour. For APIs used by AI agents, each of these has additional implications given the larger attack surface.

By Maksym Miedvied

APIs are the connective tissue of modern business systems. They connect AI agents to CRMs, portals to ERPs, and external partners to internal data. Each connection is an attack surface. Securing APIs is not an optional step — it is the baseline for operating any connected system safely.

Authentication

Every API request must be authenticated. Use OAuth 2.0 for user-facing APIs and API keys with regular rotation for service-to-service communication. Never trust unauthenticated requests, and never pass credentials in query strings.

Authorisation

Authentication confirms who is making a request. Authorisation determines what they are allowed to do. Object-level authorisation — ensuring a user can only access their own resources — is the most commonly exploited gap in API security.

Rate Limiting

Without rate limiting, APIs are vulnerable to credential stuffing, data scraping, and denial-of-service attacks. Apply limits at the user, IP, and endpoint level. Return 429 responses with appropriate retry headers.

Input Validation

Validate and sanitise every field in every request before processing. Reject unexpected data types, oversized payloads, and fields not in your API schema. This is the primary defence against injection attacks.

Encrypted Transport

All API traffic must use TLS. There are no exceptions. Redirect HTTP requests to HTTPS and reject connections with outdated TLS versions. This is table stakes — not a differentiator.

Monitoring

Log every API request with timestamp, endpoint, user identity, and response code. Set up anomaly alerts for unusual patterns — high error rates, unexpected access patterns, spikes in specific endpoints. Without monitoring, breaches go undetected.

Key Points

Authenticate every request — no exceptions
Enforce object-level authorisation so users only see their own data
Rate limit at user, IP, and endpoint level
Validate and sanitise every input field
TLS everywhere — HTTP is not acceptable for any API
Log every request; alert on anomalies in real time