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What Is Cloud WAF?

A cloud web application firewall (WAF) is a cloud-based security tool that monitors, filters, and blocks malicious HTTP traffic to and from web applications and APIs. WAFs help defend against and advanced attacks like SQL injection, cross-site scripting, credential stuffing, abusive bots, and layer 7 DDoS attacks. . Cloud-based WAFs are deployed and managed as a service at the edge, rather than housed physically in a data center.

How a cloud WAF works

While implementations vary, most cloud WAFs work as follows:

Traffic is routed through the WAF
Commonly via reverse-proxy/DNS changes, edge network integration, or via an agent-based/hybrid architecture, depending on the vendor. 

Requests are inspected and scored
The WAF analyzes request attributes like headers, parameters, patterns, client behavior and application context.

Policies and rules are applied

Managed rulesets for common vulnerabilities (like those on the OWASP Top 10) are applied. Custom rules for your application paths, APIs, login endpoints, and known bad behaviors are also applied.

Enforcement happens in real time
The WAF allows, blocks, challenges, or rate-limits requests based on detection and policy.

Logging and analytics support tuning
Teams review events, tune false positives, and tighten policies. Strong solutions will enable this effort, without slowing down releases.

Key capabilities of a cloud WAF

Key capabilities to look for in a cloud WAF include: 

  • Managed WAF rulesets, which the vendor keeps current

  • Custom rules and security policies for application and API needs

  • API protection

  • Bot mitigation, from basic automation to advanced bot defense capabilities

  • Rate limiting to reduce brute force, scraping, and abusive traffic

  • Layer 7 DDoS resilience

  • Visibility and reporting for attacks, trends, and rule efficacy

  • Integrations with things like SIEM, SOAR, CI/CD, ticketing,  and workflow support

Benefits of a cloud WAF

  • Faster time to protection: Cloud WAFs allow teams to deploy quickly and start blocking common attacks sooner.

  • Elastic scaling: Cloud WAFs can handle sudden traffic spikes or attack bursts automatically, without re-sizing appliances.

  • Reduced operations burden: Cloud WAFs require fewer upgrades and patches and less infrastructure management.

  • More current defenses: With cloud-based WAFs,  providers can push frequent managed rules and threat intelligence updates out to customers.

  • Edge proximity: By blocking closer to attackers, cloud WAFs can reduce the load on origins and improve resilience.

How is a cloud WAF different from a traditional WAF?

A non-cloud-based WAF is usually an appliance or virtual appliance you deploy and operate yourself. You must manage sizing, patching, upgrades, rule tuning, availability, and scaling. 

Instead, a cloud WAF is delivered “as-a-service,” so you can:

  • Deploy faster

  • Scale elastically with traffic spikes

  • Get continuously updated protections (managed rules and threat intel updates)

  • Reduce operational overhead by using less hardware and less resources to tune and manage the WAF

Cloud WAF vs. traditional WAF differences

Category

Cloud WAF

Traditional WAF

Deployment

Often DNS, proxy, edge integration or agents. Rollout is fast.

Appliance or VM deployment, network changes can be more labor-intensive

Scaling

Elastic by default

You size capacity, scaling requires add-ons and instances

Updates

Managed rules and threat intel frequently updated by provider

You own patching, upgrades, rule content updates 

Operations

Lower infrastructure overhead, some tuning still required

Higher infrastructure overhead, tuning and upkeep required

Performance

Often benefits from provider edge footprint, architecture of individual vendors varies.  

Depends on your placement and capacity planning

Control

Strong policy control; some managed abstractions

Deep control, but more hands-on management

Best fit

Teams that want speed, scale, and managed delivery

Regulated, legacy environments or teams needing full self-managed control

What are the use cases for a cloud WAF?

  • Protecting public web apps like marketing sites, customer portals, SaaS front end

  • Shielding API endpoints (REST/GraphQL) from abuse and injection attempts

  • Reducing credential stuffing and brute force on login and checkout flows, via rate limiting and bot management capabilities

  • Virtual patching when you can’t immediately remediate an application vulnerability

  • Mitigating Layer 7 attacks and vulnerability scanning automation

  • Supporting rapid releases where security controls must keep up with frequent changes

How Fastly can help

Fastly offers a modern web app and API security solution, with advanced protection for your applications, APIs, and microservices, wherever they live, from a single unified solution. Fastly takes a fundamentally different approach to application security, enabling increased protection without tuning, deployment anywhere you need, and industry-leading time-to-value.

You can learn more here

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