AWS WAF Challenge used to block large-scale bot attacks at the network edge

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A web security consultant was called in after a client's login page endured a week-long bot attack generating millions of requests from a vast number of IP addresses, making IP-based blocking ineffective. The attackers also rotated JA3 and JA4 fingerprints and industrialized token acquisition, partially bypassing an existing Cloudflare Turnstile integration by solving challenges in one country and replaying tokens from another. Because Turnstile validation occurred deep in the application stack, each rejected request still consumed CDN, load balancer, PHP, and database resources, driving up costs and degrading performance at scale. The consultant deployed AWS WAF's Challenge feature, which intercepts requests lacking a valid token at the network edge, before they reach any application infrastructure. This approach was applied across two attack scenarios — a legacy server-side HTML app and a modern single-page app calling a JSON API — using both integration modes offered by AWS WAF Challenge.

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