How to prevent DDoS attack against public files in S3

Preventing DDoS attacks against public files hosted in Amazon S3 involves a combination of AWS services and best practices to mitigate the risk and impact of such attacks. Here are several strategies you can implement to protect your S3 resources:

1. Use AWS CloudFront

Using Amazon CloudFront, a content delivery network (CDN), in front of Amazon S3 can help protect your files from DDoS attacks. CloudFront can absorb a significant amount of network traffic and attack patterns before they reach your S3 bucket.

• Caching: CloudFront can cache copies of your S3 content at edge locations, reducing the number of direct requests to your S3 bucket.
• DDoS Protection: CloudFront is integrated with AWS Shield, a managed DDoS protection service. AWS Shield Standard provides basic protection at no extra cost, while AWS Shield Advanced offers enhanced protections for higher-level security needs.

2. AWS WAF (Web Application Firewall)

AWS WAF can be integrated with CloudFront to provide additional layers of security controls, enabling you to block malicious web traffic based on customizable web security rules.

• Rule Configuration: Set up rules to block common attack patterns, such as SQL injection or cross-site scripting, and rules based on geographic location, IP addresses, HTTP headers, and more.
• Rate-Based Rules: Implement rate-based rules to block IP addresses that are making requests at a high frequency, which is common in DDoS attacks.

3. Logging and Monitoring

Enable logging and monitoring to detect and respond to potential DDoS activities:

• S3 Access Logs: Enable S3 bucket logging to track requests made to your S3 bucket. This can help identify suspicious patterns.
• CloudWatch: Use Amazon CloudWatch to monitor logs and set alarms based on metrics like request rates or error rates that could indicate a DDoS attack.
• CloudTrail: Use AWS CloudTrail for auditing API calls to your AWS resources, including S3.

4. Bucket Policies and IAM

Restrict access to your S3 buckets using bucket policies and IAM roles:

• Limit Permissions: Apply the principle of least privilege by granting only necessary permissions to your S3 resources.
• Secure Policies: Use secure bucket policies to prevent unauthorized access or modifications to your S3 bucket settings.

5. Origin Access Identity (OAI)

For S3 buckets used with CloudFront, configure an Origin Access Identity (OAI). This allows only CloudFront to access files in your S3 bucket, blocking direct public access to the S3 URLs.

6. Geographic Restrictions

Use geographic restrictions with CloudFront to block requests from regions from which you do not expect traffic or that are known sources of attack.

7. Scalability

Ensure your architecture is scalable to handle spikes in traffic. CloudFront and S3 are inherently scalable, but proper configuration and caching strategies are crucial to handle unexpected surges effectively.

8. AWS Shield

If you are under constant attack or require a higher level of protection:

• AWS Shield Standard: Automatically provides protection against most common DDoS attacks.
• AWS Shield Advanced: Offers additional protection against larger and more sophisticated attacks, including access to the AWS DDoS Response Team (DRT).