API Shield
What is it?
API Shield is Cloudflare's suite of tools for discovering, securing, and managing APIs (Application Programming Interfaces). As more of the internet shifts from traditional web pages to API-driven applications and microservices, API Shield ensures that APIs are protected from abuse, misuse, and attacks.
What problem does it solve?
APIs are now the backbone of the modern internet — they power mobile apps, single-page web apps, IoT devices, and machine-to-machine communication. But APIs face unique security challenges:
- They're often invisible: Unlike web pages, APIs aren't browsed by humans, making it easy to lose track of which APIs exist (sometimes called "shadow APIs").
- Traditional security doesn't fit: WAFs are designed for HTML web pages, not JSON API payloads. API attacks look different.
- Schema violations: APIs expect data in a specific format. Sending unexpected data can cause crashes, data leaks, or exploitation.
- Abuse patterns: Unlike websites, API abuse often looks like "legitimate" requests — just too many of them, or in the wrong sequence.
How does it work?
API Shield provides several layers of protection:
API Discovery: Cloudflare automatically detects all APIs your infrastructure exposes by analyzing traffic patterns — even ones you didn't know about (shadow APIs).
Schema Validation: Upload your API's schema (OpenAPI/Swagger format) and Cloudflare will reject any request that doesn't conform to the expected structure. This stops malformed or malicious payloads before they reach your server.
Mutual TLS (mTLS): Instead of just verifying the server's identity (standard TLS), mTLS also verifies the client's identity using certificates. This is critical for IoT devices and machine-to-machine communication where there's no username/password.
Sequence Detection: Monitors the order of API calls to detect abuse patterns. For example, a legitimate user would browse products before checking out — a bot might skip straight to the checkout endpoint.
Rate Limiting: API-specific rate limiting to prevent abuse without affecting legitimate users.
Why it matters strategically
API traffic is growing much faster than traditional web traffic, and it's becoming the primary attack surface for most organizations. API Shield positions Cloudflare as the security layer for the entire modern application stack, not just traditional websites. This is important for expanding Cloudflare's relevance with enterprise customers who are increasingly API-first.