Protecting OTP & Magic Link Endpoints from Abuse: IP Reputation, Rate Limiting, and Suspicious IP Throttling

OTP and magic link endpoints are attractive targets for bots and fraudsters because they're exposed before full authentication. A layered defense strategy is essential, combining IP reputation analysis (filtering datacenter IPs, VPNs, TOR nodes, and known bad actors), dynamic risk scoring (0–100+ scale with proportional responses), rate limiting (3–5 requests per IP/email per minute), and IP throttling to gradually slow suspicious traffic. Simple allow/block approaches are obsolete against modern distributed attacks using residential proxy networks. Effective protection correlates multiple signals—geolocation, device fingerprinting, behavioral velocity, email/phone reputation—in real time to block abuse while preserving legitimate user experience. Failure to secure these endpoints risks fake account inflation, SMS/email cost abuse, MFA fatigue attacks, and regulatory non-compliance under GDPR, SOC 2, and PCI DSS.