We are pleased to announce the General Availability (GA) of the JavaScript Challenge feature for Azure Web Application Firewall (WAF) on Azure Front Door. This capability equips organizations with a seamless, invisible anti-bot verification layer that distinguishes legitimate users from malicious scripts helping protect web applications from automated threats while preserving a smooth user experience.
Azure WAF JavaScript Challenge
Modern bot attacks are increasingly evasive, often bypassing traditional defenses like IP based blocking or simple rate limits. The JavaScript Challenge introduces a lightweight, browser-based verification step that helps distinguish legitimate users from automated scripts without requiring user interaction. Benefits of the JavaScript Challenge include:
- Low friction for legitimate users: Genuine users experience minimal latency or interruption since no manual interaction is required.
- Stronger bot protection: Automated tools and scripts fail to pass the computational challenge, enabling more effective blocking of bad bots.
- Flexible enforcement: You can target specific endpoints (e.g., login, registration, checkout flows), apply to bot manager or custom rules, and adjust cookie lifetimes to align with your user experience goals.
How JavaScript Challenge Works
The JavaScript Challenge is configured as an action in either custom rules or in the Bot Manager ruleset. When a client’s HTTP/S request matches a rule with this action, Azure WAF directs the browser to a lightweight challenge page. The page runs a short computational task automatically usually invisible to the user.
If the browser successfully completes the computation, the request is validated and allowed to proceed, confirming that it originated from a legitimate user. If the challenge fails, the request will be blocked, preventing automated bots from accessing the application.
Getting Started
If you have been using JavaScript Challenge during the public preview, your existing configurations will continue to work. For new users, simply enable the JavaScript Challenge action in your WAF policy and define the triggering conditions.
For more details on configuration and best practices, check out our earlier blogs:
- Azure WAF Public Preview: JavaScript Challenge | Microsoft Community Hub
- Azure WAF’s Bot Manager 1.1 and JavaScript Challenge: Navigating the Bot Threat Terrain | Microsoft Community Hub
Documentation
Microsoft