AWS WAF: A Deep Dive — Managed Rules, Rate Limiting, and Bot Protection for Web Defense (with GCP Cloud Armor & Azure WAF Comparisons)
Introduction: A WAF Isn’t a “Last Line of Defense”—It’s an Operational System That Works Through Design
As a web app or API grows, attacks tend to evolve from “messy” to “practical.” Beyond classic threats like SQL injection and XSS, you’ll increasingly see traffic that directly harms the business: automated login attempts, scraping, inventory/reservation hoarding, and high-frequency abuse of search endpoints. For these application-layer (Layer 7) threats, AWS WAF (Web Application Firewall) is a powerful way to add controls in the cloud quickly while keeping governance manageable. 0
AWS officially describes AWS WAF as a service that monitors HTTP(S) requests forwarded to protected resources and takes actions such as allow, block, or count (detect-only) based on defined conditions. Supported resources include CloudFront, API Gateway (REST API), Application Load Balancer, AppSync, Cognito, App Runner, Verified Access, Amplify, and more. 1
This article goes a step beyond “just turning it on” and explains—in practical terms—how to assemble rules, reduce false positives, understand cost structure, and design logging/operations. It also lines up GCP Cloud Armor and Azure Web Application Firewall (WAF) so your decision-making stays consistent even in multi-cloud environments. 2
Who This Helps: Which Teams Benefit Most
1) App development teams (backend/frontend) who tend to “push security to later”
WAFs can look like security-only tooling, but in practice they’re deeply tied to app quality. Rate-limit abused search APIs, reduce login bots, and block known exploit patterns early—these improve availability and cost as much as security. AWS WAF is commonly introduced as supporting blocks for general patterns like SQLi and XSS, as well as monitoring/blocking/rate limiting for bots. 3
2) SRE/operations teams who struggle to distinguish “attack vs. bug” during incidents
When traffic spikes, it’s easy to hesitate: DDoS-like behavior, social media virality, bots, or an app regression? With WAF logs and disciplined rule operation, triage becomes much faster. Think of the WAF not just as monitoring, but as an operational audit trail.
3) IT/security teams who must provide “defensible controls” for audits and customer requirements
Saying “we use a WAF” is increasingly insufficient. You’re asked what rules you use, how you manage false positives, and how exceptions are governed. AWS WAF’s pricing and control model (Web ACLs, rules, request counts) makes it comparatively straightforward to document in designs and audits. 4
1. AWS WAF Overview: Define “What Requests Are Allowed” with Web ACLs and Rules
The core unit in AWS WAF is the Web ACL (Access Control List). Within a Web ACL, you place rules (or rule groups). For each incoming request, AWS WAF evaluates the rules in order and applies actions such as allow/block/count when conditions match.
Operationally, “evaluate rules in order” matters a lot because what should be blocked vs. allowed depends on how your application works. For example, CMS or search-heavy applications may naturally include many symbols in query strings, which can trigger false positives in managed rules. AWS notes that managed rules can save time, but it’s realistic to assume from day one that you’ll need app-specific tuning. 5
2. What You Can Protect: Put AWS WAF at the “Entrance” First
AWS WAF monitors HTTP(S) requests forwarded to protected resources and can be attached to multiple “entry” services such as CloudFront, API Gateway (REST API), and Application Load Balancer, among others. 6
A practical approach is simple:
- Identify every external entry point (CDN, load balancer, API endpoints, etc.)
- Place WAF at those entry points so traffic can be stopped before reaching the app
- Split responsibilities: the WAF blocks what it can at the edge; the app handles authorization and app-native controls
Because a WAF isn’t omnipotent, deciding early what “belongs to the app” vs. “belongs to the WAF” prevents rule design from drifting.
3. Rule Design Basics: Start with “Managed Rules + Rate Limiting”
A major advantage of AWS WAF is that you don’t need to build everything from scratch with regex rules. You can use managed rule groups for common attacks and add custom rules only where needed. AWS documentation and product materials commonly highlight coverage for general patterns like SQLi and XSS and emphasize time-saving managed rules. 7
Recommended order of implementation (least likely to cause conflict in real teams)
- Start with Count (detect-only)
If you jump straight to Block, false positives can lock out legitimate users. Start with Count, collect logs, and learn what triggers which rules. - Add Rate-based rules (rate limiting)
High-frequency abuse is valuable to suppress early even when it’s hard to classify. Works well for login, search, password reset, inventory checks, etc. - Add business-driven exceptions (Allow / scope-down)
Explicitly encode operational needs: admin IP allowlists, health check exclusions, specific paths, etc.
This sequence lets you strengthen WAF safely while improving the app side in parallel (input validation, response behavior, bot resilience).
4. Understanding Cost: WAF Cost Builds on “Web ACLs, Rules, Requests”
AWS WAF pricing is described in terms of a monthly fee per Web ACL, a monthly fee per rule (or rule group), and charges per number of processed web requests (per million). U.S. pricing pages often illustrate values like $5/Web ACL/month, $1/rule/month, and $0.60 per million requests, with example calculations. 8
Key cost-control levers:
- Don’t over-fragment Web ACLs (necessary boundaries are fine, but excessive splitting increases fixed cost)
- Avoid rule sprawl (duplicate intent across many rules bloats cost and operations)
- High-traffic entry points make rule efficiency important (avoid over-inspecting everything)
Also note: bot-focused add-ons (e.g., Bot Control) may be priced separately depending on what you enable, so clarify requirements before estimating. 9
5. Practical Templates: Keep These Three “Patterns” Ready
Below are adoption patterns that are easy to share within teams. The focus is the thinking, not the exact code.
Template A: Minimal set for APIs — “Managed Rules + Rate Limiting”
Goal: Block classic attacks (SQLi/XSS) and rate-limit abuse-prone APIs.
- Rule 1: AWS-managed rule group (start with Count → move to Block after validation) 10
- Rule 2: Rate limiting for
/loginand/password-reset(e.g., per-IP N requests per minute) - Exceptions: allow internal IPs and monitoring health checks (Allow / scope-down)
This is especially effective for products that prioritize speed: stop high-impact bad traffic first instead of seeking perfect classification.
Template B: For static sites/frontends — Organize by “Country / IP / Path”
Goal: Reduce attack volume when it’s concentrated in certain regions or networks.
- Rule 1: Geo-based blocks for clearly irrelevant countries
- Rule 2: Block known bad IP ranges (kept in an updatable operational format)
- Rule 3: Admin paths (e.g.,
/admin) block everyone except allowlisted IPs/VPN
Geo-blocking often collides with business goals, so record the decision rationale (“which countries and why”) to avoid future conflict.
Template C: When false positives are scary — “Count → staged Block” operation
Goal: Prevent UX damage from false positives right after deployment.
- Weekly review of Count logs to identify false positives
- Add exceptions (path/header/query-based)
- Promote only clearly malicious rules to Block first
- Keep uncertain rules in Count (accept “configured but not enforced” as a valid state)
WAF strength comes from operational strengthening over time, not from trying to ship a perfect ruleset on day one.
6. AWS WAF vs. AWS Shield: Different Layers, Clear Division of Roles
AWS guidance commonly frames AWS WAF as filtering HTTP/S traffic at the application layer (Layer 7) to protect web apps and help address common web attacks such as SQLi/XSS/CSRF. 11
This distinction matters: trying to solve large-scale network-layer DDoS purely with WAF can distort your design. Keep the division clear: use WAF for Layer 7 attacks/bots/malicious patterns, and rely on other protections (service capabilities / DDoS protection) for large network-layer events.
7. Comparison with GCP Cloud Armor: Operate WAF + DDoS Protection via “Policies”
GCP Cloud Armor is often discussed as combining WAF and DDoS protection. Its pricing pages present axes such as “security policy (protected resource)” and “requests (per million).” 12
Enterprise-level materials also describe pricing in units like policies/rules/requests and may include baseline fees (e.g., monthly per project) and per-protected-resource charges. 13
A helpful comparison framing:
- AWS: You “stack” Web ACLs and rules (rule groups) 14
- GCP: You manage around security policies, tying them to protected resources and requests 15
In practice, both share the same operational essence: filter at the entrance, encode exceptions, and tune via logs. The differences show up most in pricing units and management structure.
8. Comparison with Azure WAF: Choose It Together with Your “Entrance Service”
Azure’s Web Application Firewall is often presented as part of Azure Front Door Premium, and pricing structures may include fixed monthly elements plus request-based components (depending on the service edition). 16
English pricing materials also show items like time-based billing for WAF policy (e.g., hourly) tied to specific gateway products, illustrating how WAF cost and structure are linked to the entry service. 17
In Azure, the “shape” of the decision often depends on the entrance:
- Do you want global/CDN-style protection (Front Door)?
- Or regional load-balancer-style protection (Application Gateway)?
- Do you already have that entrance service, or are you selecting it now?
Because pricing and capabilities are bundled with the entrance service (or WAF policy time billing), it’s especially important to finalize the entrance architecture early. 18
9. Stable Multi-Cloud Comparison Axes: Use These 6 Criteria
Before getting lost in fine feature differences, align evaluation with these six items:
- Where it sits (entry resource)
- What it stops (SQLi/XSS, bots, rate limiting, geo/IP restrictions, etc.) 19
- How exceptions are created (admin panels, health checks, legitimate crawlers)
- False-positive operations (Count → staged Block, review cadence)
- Logging/audit design (who reviews, where stored, retention)
- Pricing units (AWS: Web ACL/rules/requests; GCP: policy/requests; Azure: often tied to entrance services) 20
Once these six are aligned, your “decision foundation” stays consistent across clouds, and meetings become dramatically easier.
10. Conclusion: AWS WAF’s Value Comes from How You “Grow It,” Not How You “Install It”
AWS WAF is officially described as a WAF that monitors HTTP(S) requests and controls them by conditions, and it can be applied to multiple entry services like CloudFront, API Gateway, and ALB. 21
Its strengths include leveraging managed rules for common attacks like SQLi/XSS and addressing real-world nuisance traffic through bot monitoring/blocking/rate limiting. 22
Because pricing accumulates based on Web ACLs, rules (rule groups), and request volume, you can forecast cost behavior relatively clearly during design. 23
GCP Cloud Armor tends to be policy-centered in both management and pricing expression, while Azure WAF is frequently evaluated in tandem with Front Door or Application Gateway (entrance services). 24
Still, the core is consistent across clouds: “block what you can at the entrance, tune false positives operationally, and encode exceptions as rules.” That’s what creates durable defense.
If you want a practical next step, start with just one:
- Enable a managed rule group in Count mode and visualize false positives for one week
- Add rate limiting to abuse-prone APIs like login/search
- IP-restrict the admin entrance and turn “exceptions” into rules (not just procedures)
Start small—but operate carefully. Done that way, a WAF grows into a reliable system that improves not only security, but also availability and cost control.
Reference Links (Official Sources-Focused)
- AWS WAF (Developer Guide: Overview) 25
- AWS WAF (Product Page) 26
- AWS WAF Pricing (Global) 27
- AWS WAF Pricing (Japanese) 28
- Choosing AWS WAF vs. AWS Shield (Decision Guide) 29
- Google Cloud Armor Pricing 30
- Cloud Armor Enterprise Overview (Pricing Model Thinking) 31
- Azure Web Application Firewall Pricing (Japanese) 32
- Azure Web Application Firewall Pricing (English) 33