AWS Best Practices for DDoS Resiliency - Attack Surface Reduction | Deep Dive.

Here’s twtech deep dive into AWS Best Practices for DDoS Resiliency- Attack Surface Reduction.

Focus:

•        Explaining the why, how, and architecture patterns across the stack (Edge → Application → Origin).

 Breakdown:

•        Concept Overview of Attack Surface Reduction,
•        Core AWS Architecture Layers,
•        Edge Layer (Public Entry Points),
•        Application Layer (Controlled Access & Authentication),
•        Origin Layer (VPC & Resource Protection),
•        Control Plane (IAM & Governance),
•        Sample Attack Surface Reduction Flow,
•        Monitoring and Continuous Hardening,
•        Combined Defense Strategy.

Concept Overview of Attack Surface Reduction

Goal:

•        Minimize the number of entry points and resources that can be targeted by an attacker.
•        This is the first  layer of AWS DDoS Resiliency Strategy , before detection or mitigation, reduce what can be attacked.

Attack Surface Reduction is about:

•         Limiting public exposure.
•         Isolating sensitive resources.
•         Using AWS-managed entry points that are inherently more resilient.
•         Enforcing least privilege and scoped access.

 Core AWS Architecture Layers

1. Edge Layer (Public Entry Points)

Best Practices

Practice	Description	AWS Services
Use AWS Edge Services as primary entry points	Terminate all external requests at AWS-managed edge (CloudFront, Global Accelerator, Route 53) instead of direct access to origins.	Amazon CloudFront, AWS Global Accelerator, Amazon Route 53
Avoid exposing IPs directly	Do not allow direct traffic to EC2 or ALB public IPs. Always front them with CloudFront or GA.	AWS Shield, CloudFront
Use AWS WAF and Shield Advanced	Protect against application and network layer DDoS before it reaches your origin.	AWS WAF, AWS Shield Advanced
Geographic restriction	Limit requests to specific countries or regions to reduce threat vectors.	CloudFront Geo Restriction
Rate limiting and token validation	Reduce abuse of unauthenticated endpoints.	WAF rate-based rules, Lambda@Edge token checks

 Sample Architecture

2. Application Layer (Controlled Access & Authentication)

Best Practices

Practice	Description	AWS Services
Authenticate early	Use Cognito or OIDC before application logic to reject unauthenticated traffic fast.	Amazon Cognito, API Gateway Authorizers
Use private APIs where possible	Internal or partner traffic should not use public endpoints.	API Gateway Private Endpoints, VPC links
Use tokenized or signed URLs	Prevent hotlinking and unauthorized requests.	CloudFront Signed URLs/Cookies
Cache responses	Reduce load on origin by leveraging CloudFront caching and Lambda@Edge normalization.	CloudFront, Lambda@Edge
Minimal open ports & protocols	Only expose ports required (e.g., HTTPS 443). Disable 80 unless redirecting.	Security Groups, Network ACLs

 Additional Strategies

•         Block unwanted HTTP methods (PUT, TRACE, etc.)
•         Validate input lengths and headers to block malformed or oversized requests.

3. Origin Layer (VPC & Resource Protection)

Best Practices

Practice	Description	AWS Services
Use private VPC subnets for origins	Keep application servers and databases isolated from the internet.	Amazon VPC, Private Subnets
Use VPC endpoints for AWS service calls	Avoid public endpoints for S3, DynamoDB, etc.	VPC Endpoints
Restrict access via Security Groups & NACLs	Allow traffic only from CloudFront or ALB security groups.	AWS Security Groups, NACLs
Auto Scaling & Load Balancing	Automatically absorb volumetric spikes (legitimate or attack).	EC2 Auto Scaling, ALB, ECS
Limit Route 53 exposure	Use private hosted zones for internal resolution.	Route 53 Private Zones

4. Control Plane (IAM & Governance)

Best Practices

Practice	Description	AWS Services
Use least privilege IAM	Prevent attackers from exploiting misconfigured identities.	AWS IAM, SCPs
Centralize management of edge protections	Manage CloudFront, WAF, and Shield configurations via IaC or AWS Firewall Manager.	AWS Firewall Manager
Enable logging and monitoring	Visibility is key for rapid response and forensic analysis.	CloudWatch, CloudTrail, WAF logs, S3 access logs

 Sample Attack Surface Reduction Flow

NB:

•        Only CloudFront is public.
•        All downstream resources are reachable only via trusted AWS infrastructure, dramatically reducing the exposed attack surface.

 Monitoring and Continuous Hardening

Category	Tools		Purpose
Edge Traffic		CloudFront + WAF logs	Identify attack patterns
Origin Access		VPC Flow Logs	Detect unauthorized access attempts
Security Events		GuardDuty + Security Hub	Automated threat detection
Compliance		AWS Config	Detect drift in public exposure
Remediation		Lambda or Systems Manager Automation	Auto-remediate security group misconfigurations

Combined Defense Strategy

Attack Surface Reduction works in tandem with:

1.     Resilient Architecture – Auto Scaling, distributed deployment, stateless workloads.

2.     Detection & Mitigation – Shield Advanced, WAF anomaly detection.

3.     Response & Recovery – Runbooks, playbooks, AWS SRT engagement.