速率限制与 DDoS 防护

Protecting your edge applications is crucial. In this lesson, we'll explore two powerful security mechanisms: Rate Limiting and DDoS Protection.

These features help keep your applications stable, secure, and available, even under heavy load or malicious attacks.

Rate limiting controls how many requests a user or IP address can make to your application within a specific timeframe. It's like a bouncer, ensuring fair access and preventing abuse.

• Prevent Abuse: Stops bots and malicious actors from scraping data or brute-forcing logins.
• Protect Resources: Reduces strain on your serverless functions and databases.
• Control Costs: Limits excessive usage that could lead to higher billing.

Cloudflare offers robust, configurable rate limiting directly at the edge. This means requests are evaluated and potentially blocked before they even reach your Worker or origin server.

You can define rules based on various criteria like URL path, HTTP method, IP address, and even custom headers.

When setting up a rate limit, you typically define:

• Threshold: The maximum number of requests allowed (e.g., 100 requests).
• Period: The time window over which the threshold applies (e.g., 60 seconds).
• Action: What happens when the limit is exceeded (e.g., block, challenge, or log).
• Matching Criteria: Which requests the rule applies to (e.g., specific URL, method).

Imagine you want to protect your login endpoint from brute-force attacks. You could set a rule like this:

If: 10 requests to "/api/login"
From: The same IP address
Within: 60 seconds
Then: Block the IP for 5 minutes

This simple rule significantly enhances your application's security against common threats.

A Distributed Denial of Service (DDoS) attack aims to overwhelm your application or server with a flood of traffic, making it unavailable to legitimate users.

Unlike simple rate limiting, DDoS attacks often come from many different sources (a "botnet"), making them harder to defend against manually.

Cloudflare provides always-on DDoS protection that automatically detects and mitigates attacks across its global network. This happens transparently, often without you needing to configure anything specific.

It works by analyzing traffic patterns, identifying malicious requests, and filtering them out before they reach your infrastructure.

Cloudflare offers different security levels you can adjust for your domain, impacting how aggressively it challenges suspicious traffic:

• Essentially Off: Minimal protection.
• Low: Challenges the most threatening visitors.
• Medium: Challenges moderate threat visitors.
• High: Challenges all visitors that have previously exhibited threatening behavior.
• I'm Under Attack!: Challenges all visitors to mitigate advanced DDoS attacks.

Consider the following scenarios. Which security measure is best suited to address each?

You've learned how Rate Limiting prevents abuse and resource exhaustion from individual sources, while DDoS Protection shields your application from large-scale, coordinated attacks.

Leveraging Cloudflare's edge capabilities for these features means your applications are more resilient, performant, and secure right where they need to be.