Network security threats are increasingly complex, and the content delivery network is the first line of defense for enterprise traffic, and its security configuration directly affects service availability and data security. IP whitelisting and geo-blocking are the core tools of CDN security policy, which can effectively defend against malicious attacks, control access rights, and meet compliance requirements. How to achieve precise deployment of CDN access control?
1. Adaptation of basic principles to scenarios
The essence of IP whitelisting and geo-blocking is to filter traffic through the rule engine. IP whitelists allow only specified IP addresses or IP address segments to access resources. The whitelist applies to scenarios where access permissions are strictly restricted, such as the management background and API interfaces. Geolocation is based on IP geolocation databases (such as MaxMind GeoIP) to block or pass requests from specific countries, often to meet data sovereignty regulations (such as GDPR) or to defend against regional attacks.
Typical application scenarios include API interface defense, which allows only partners' IP addresses to invoke critical interfaces to prevent unauthorized access. Financial compliance to limit cross-border user access to sensitive data and avoid legal risks; DDoS mitigation blocks IP address segments in areas with high incidence of attack sources to reduce the impact of malicious traffic. Content distribution control, blocking video streaming requests in specific areas based on copyright agreements.
2. Detailed explanation of mainstream CDN platform configuration
Cloudflare
1. Set the IP whitelist
The Firewall Rules page is displayed, and a new rule is created.
Conditions: IP Source Address Select in List and enter the allowed IPv4/IPv6 address (support CIDR format, such as 192.168.1.0/24).
Operation Select Allow and set the priority to the highest (minimum) value to ensure that the whitelist matches the priority.
After saving, synchronize to the global edge node (takes effect in about 30 seconds).
2. Configure geographic blocking
Add a condition to the firewall rule: 'Country' selects the target country (for example, "CN" stands for China);
The action selects "Block" or "Challenge," the latter filtering the robot by captCHA;
Rules can be refined in conjunction with ASN (Autonomous System Number), such as blocking abnormal traffic from a specific ISP.
Note: The free edition only supports country-level blockades, while the Enterprise edition can be refined to cities or ASN.
3. fine strategy design and risk avoidance
Dynamic IP processing scheme
When a user's IP address changes dynamically (for example, a floating IP address is assigned by a mobile terminal or ISP), the traditional whitelist may become invalid. In this case:
Two-way certificate authentication: the client installs a private certificate, and the CDN verifies the validity of the certificate.
Token verification: Add a dynamic token (such as JWT) to the request header to verify the validity of CDN edge nodes;
Behavior analysis: Combine UserAgent, request frequency and other characteristics to identify legitimate traffic through machine learning.
False seal and missing seal response
Log monitoring: Periodically analyze CDN access logs (such as S3 logs of AWS CloudFront) to identify legitimate IP addresses that are intercepted by mistake. Gray release, the new rule is first applied to the test domain name, verified and synchronized to the production environment; Emergency channel: Retain the whitelist of the management IP address segment to ensure that you can log in to the console to adjust the configuration even after being blocked.
Balance of performance and security
Layered protection is the front-end CDN for coarse-grained blocking (such as national level), back-end WAF for fine-grained rule matching (such as URL path, request parameters); The edge computing logic uses Cloudflare Workers or AWS Lambda@Edge to execute custom interception scripts on edge nodes to reduce back source latency. The caching policy optimizes that requests to blocked areas return static error pages (HTTP 451) to avoid penetrating the source site and consuming resources.
4. Advanced scenarios and compliance practices
Compliance adaptation for multinational enterprises
Data localization requirements: geoblocking ensures that EU user requests are processed only by nodes in Frankfurt or Ireland and data storage is GDPR compliant;
Copyright content distribution: Dynamically return differentiated video content based on the user's IP country (such as Netflix's regional copyright policy).
Defend against large-scale DDoS attacks
The IP reputation database integrates Spamhaus or AbuseIPDB database to automatically block historical malicious IP addresses. Rate Limiting: Set the threshold of "requests per client IP per second" in Cloudflare (such as 10 per second), beyond which JS challenge or direct blocking is triggered; The Smart Threat Score enables Cloudflare's threat Score to implement progressive interception (from questioning to outright banning) of high-risk IP.
The IP whitelisting and geo-blocking configurations must be dynamically adjusted based on service features, threat intelligence, and compliance frameworks. With the popularity of IPv6 and the development of edge computing, the traditional IP-based protection mode may face challenges (such as the dynamic nature of IPv6 addresses). Enterprises need to establish continuous monitoring and iteration mechanisms, find the best balance between security, performance and user experience, and build a truly intelligent CDN security ecology.
