Module 14 · API DDoS & Bot Mitigation

Manish Garg
Manish Garg Associate of (ISC)² · RingSafe
Apr 27, 2026
1 min read
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Last updated: April 29, 2026

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Why this module. APIs are bot magnets. Credential stuffing against /login, scraping of /products, account creation abuse, comment spam. Volumetric DDoS is solved at the edge; L7 abuse is a per-API battle.

Why this module. APIs are bot magnets. Credential stuffing against /login, scraping of /products, account creation abuse, comment spam. Volumetric DDoS is solved at the edge; L7 abuse is a per-API battle.

Bot patterns by endpoint

  • /login — credential stuffing, brute force
  • /signup — fake account creation for fraud / spam
  • /api/search — scraping / SEO attacks
  • /api/products — competitor scraping, price crawling
  • /api/checkout — gift-card cracking, CVV cracking
  • /forgot-password — account-existence enumeration

The defence layers

  1. Edge rate limiting — Cloudflare, AWS WAF. Per IP, per ASN. Easy.
  2. Authenticated rate limiting — per user account. Harder but more accurate.
  3. Behavioural fingerprintingTLS handshake (JA3/JA4), HTTP/2 fingerprint, browser-traits. Catches headless browsers.
  4. CAPTCHA / challenges — hCaptcha, Turnstile, reCAPTCHA Enterprise. Cost the bot, not the human.
  5. Anomaly — UEBA-style on API events. Account suddenly searches 10K SKUs in an hour.

Per-endpoint patterns

  • /login — strict rate limit per username (3-5 attempts/15 min); CAPTCHA after threshold; account lockout on extreme.
  • /signup — CAPTCHA + rate limit per IP + new-account-anomaly detection (signups from same IP in close time).
  • /api/products — auth required + per-user rate limit + bot-detection on user-agent + TLS fingerprint.
  • /forgot-password — return same response whether email exists or not (prevent enumeration); rate limit per email.

The bot business model

Sophisticated bots use residential proxy networks (real ISPs, real IPs). Each IP makes 1-2 requests/min. Aggregate hits your endpoint hard. Per-IP rate limiting fails entirely.

Defences that scale: ASN-level limits + behavioural fingerprinting + authenticated requests only.

Defender’s checklist

  • Per-endpoint rate-limit policies tuned to expected traffic.
  • Per-account limits in addition to per-IP.
  • Bot management (CDN-tier or dedicated).
  • Anomaly detection on authenticated traffic.
  • CAPTCHA for unauthenticated sensitive endpoints.
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