Enable and configure JavaScript Challenge
Implementation Effort: Low
User Impact: Medium
Overview
Bots generate a significant portion of internet traffic and are a common source of application abuse, including credential stuffing, scraping, and denial‑of‑service conditions that directly impact availability and business operations. When left unchecked, automated traffic can overwhelm application resources, degrade user experience, and increase operational risk.
The JavaScript Challenge in Azure Web Application Firewall (WAF) provides a lightweight, browser‑based verification mechanism that validates client behavior before access to protected application resources is allowed. When a request matches a rule configured with this action, the client browser must complete a short JavaScript computation; requests that fail the challenge are blocked. JavaScript Challenge can be applied through Bot Manager managed rules or custom WAF rules, enabling targeted protection for high‑risk endpoints such as authentication, registration, and checkout flows. This capability aligns with Zero Trust principles by verifying clients explicitly and assuming breach, while preserving a low‑friction experience for legitimate users.