Hackers use FastHTTP in new high-speed Microsoft 365 password attacks

SpearTip discovered a global automated brute-force campaign (starting 2025-01-06) that uses the FastHTTP Go library to target Azure AD / Microsoft 365 sign-ins and to execute MFA‑fatigue attacks; actors achieve roughly a 9.7–10% successful account takeover rate, with most malicious traffic originating from Brazil. The report details attack telemetry, success/failure breakdowns, recommended detection steps (PowerShell and Sign-in log filters), and remediation actions (expire sessions, reset credentials, review MFA devices).