waf

SKILL.md

AWS WAF

Overview

Domain expertise for configuring AWS WAF, the web application firewall that filters HTTP and HTTPS
traffic to CloudFront distributions, Application Load Balancers, API Gateway REST APIs, and AppSync
GraphQL APIs. Covers web ACL creation and association, AWS Managed Rules, rate-based rules, match
rules (IP set and geographic), Bot Control and the signal-forwarding workflows built on top of it,
Fraud Control for logins and signups, AI and LLM crawler management, and the logging that every
tuning workflow depends on.

This skill is a router. Each customer task maps to a procedure file under references/. Read the
matching reference in full before acting, then follow its constraints and steps. The reference
files are self-contained: each carries its own decision tables, constraints, procedure, and
troubleshooting.
Execute commands using the AWS MCP server when connected (sandboxed execution, audit logging,
observability). Fall back to the AWS CLI otherwise. A web ACL's scope is fixed at creation: a
CloudFront web ACL must be created in us-east-1 with CLOUDFRONT scope, while a regional web ACL
(Application Load Balancer, API Gateway, AppSync) is created in the resource's Region with
REGIONAL scope.

Which WAF task do you need?

Goal
Reference

Create a web ACL and attach it to a resource
creating a web ACL and associating it with a resource

Set up logging and sampling before tuning anything
setting up logging and request sampling

Add AWS Managed Rules and tune false positives
adding managed rules and tuning with count mode

Throttle HTTP floods and brute force
adding rate-based rules

Allow or block by IP range or country
using ip sets and geographic match rules

Detect and control bots (the on-ramp)
protecting against bots with bot control

Collapse bot labels into one confidence signal
turning bot control labels into a confidence signal

Forward all signals to the origin with one rule
forwarding signals with dynamic label interpolation

Decide what the app does with the forwarded signal
adaptive mitigation playbook for forwarded signals

Stop attackers from spoofing forwarded headers
stripping inbound waf headers before trusting them

Recover the real client IP behind a CDN
recovering the real client ip behind a cdn

Protect logins and signups from fraud
protecting logins and signups with fraud control

See and manage AI and LLM crawler traffic
seeing and managing ai crawler traffic

Routing notes

Logging comes before tuning. Every Count-mode tuning workflow assumes logging and request
sampling are on. If the customer has not set up logging, run that reference first; otherwise
Count-mode tuning has nothing to read.

Web ACL scope is fixed at creation. A CloudFront web ACL is CLOUDFRONT scope in
us-east-1; a regional resource needs a REGIONAL web ACL in its own Region. Scope cannot be
changed later, so the creating reference settles it before anything is built.

Bot Control is a chain, not one task. Protecting against bots is the on-ramp (turn on, choose
Common vs Targeted, observe). Turning labels into a confidence signal, forwarding that signal,
and deciding what the application does with it are three separate references that build on it in
that order. The header-stripping reference is the mandatory safety companion whenever a signal is
forwarded to the origin.

Common vs Targeted is not a soft choice. Common only catches self-identifying bots and
known-bad IPs. For login, checkout, or any high-value endpoint facing evasive bots, Targeted with
the application integration SDK is required. The bots reference pushes Targeted for real bot
threats rather than presenting it as optional.

Rate limiting vs Fraud Control. Rate-based rules blunt volumetric HTTP floods. Credential
stuffing and fake-account creation are account-based abuse that rate limiting misses; those go to
the Fraud Control reference (ATP and ACFP), not the rate-based reference.

Forwarded headers need the strip rule. Any time the customer forwards a signal or the client
IP to the origin in x-amzn-waf-* headers, the inbound-header-stripping reference is required to
prevent spoofing. The confidence-signal, interpolation, and client-IP references all point at it.

What lives in other skills. L3/L4 DDoS protection and Shield cost-protection credits are the
shieldadvanced skill. Multi-account WAF rollout is the firewallmanager skill. CloudFront and
Application Load Balancer configuration are their own skills. This skill builds the WAF rules; it
does not configure the resources it protects.

Security Considerations

AWS WAF is itself a security control, so misconfiguration directly weakens an application's defenses.
Apply these across every reference:

Least-privilege IAM. You MUST grant only the specific wafv2: actions a task needs (for
example wafv2:CreateWebACL, wafv2:GetWebACL, wafv2:UpdateWebACL, wafv2:AssociateWebACL,
wafv2:PutLoggingConfiguration) rather than wafv2:* or the AWSWAFFullAccess managed policy.

Ephemeral credentials. You MUST use IAM roles with temporary credentials (such as an EC2
instance profile, SSO session, or aws sts assume-role) rather than long-lived IAM user access
keys when running these WAF CLI commands.

Monitor configuration changes. You SHOULD enable AWS CloudTrail on wafv2 management events
and set CloudWatch alarms on critical web ACL configuration changes (such as DeleteWebACL and
UpdateWebACL rule removals) and on the web ACL's BlockedRequests and CountedRequests
metrics, so rule changes and sudden spikes in blocked or counted traffic are detected.

Misconfiguration opens access. A web ACL that is created but never associated, or one whose
default action is left at Allow with no enforcing rules, filters nothing. You MUST confirm the
web ACL is associated and that its posture matches the intended default (block vs allow) before
reporting setup complete.

Protect log destinations. Logs can capture credentials and session data. You MUST redact
sensitive fields (such as the authorization header and cookie) and MUST enable encryption at
rest on the log destination (CloudWatch Logs, Amazon S3, or Amazon Data Firehose).

Header-spoofing risk. Any x-amzn-waf-* signal forwarded to the origin can be forged inbound.
You MUST add the inbound-header-stripping rule whenever a signal or client IP is forwarded (see
stripping-inbound-waf-headers-before-trusting-them).

Additional Resources

AWS WAF Developer Guide

How AWS WAF works (AWS WAF Developer Guide)

AWS WAF pricing