Use this page to find answers to common security questions about Alibaba Cloud CDN.
Security
Block and filter traffic
How do I block malicious requests from specified IP addresses? Add specific IP addresses to an IP blacklist so CDN rejects their requests before they reach your origin server.
Why can an IP address in the IP blacklist still be used to request resources? IP blacklist rules have specific propagation and matching behaviors. Learn why a listed IP may still get through and how to address it.
Troubleshoot HTTP errors
Why is the HTTP 503 status code caused by the security features that are configured for the origin server returned when users access my domain name? Your origin server's own security rules may be blocking CDN edge nodes. Learn how to identify the cause and allowlist CDN IP ranges.
Why is the HTTP 403 status code returned to users when hotlink issues are detected? Hotlink protection is blocking the request because the Referer header doesn't match your allowlist. Learn how to troubleshoot and update your hotlink protection rules.
Defend against DDoS and HTTP flood attacks
How can I protect domain names accelerated by Alibaba Cloud CDN from DDoS or HTTP flood attacks? Configure rate limiting and integrate with Anti-DDoS to defend accelerated domain names against DDoS attacks and HTTP flood attacks.