Microsoft 365 Token-Replay Attacks Compromise 97 Accounts at 79 Organizations
AI-summarised brief · reviewed before publication
Researchers at Huntress uncovered a Microsoft 365 token‑replay campaign that hijacked sign‑in sessions and replayed stolen access tokens to infiltrate 97 accounts across 79 organizations between July 14 and September 22, 2026. The attackers used an adversary‑in‑the‑middle login page to capture credentials and MFA codes, then harvested the resulting tokens and “sprayed” them at scale, achieving 497 successful sign‑ins from over 200,000 attempts traced to the 193.26.115.0/24 subnet. After gaining access, they added rogue authenticator apps and registered 48 fake Entra devices to maintain persistence, sometimes removing existing MFA within three hours. Hidden email rules were also deployed to delete or forward messages, and compromised mailboxes were used to send spam before Microsoft Entra ID Protection flagged the accounts as high risk. The operation originated from a Romanian IP linked to the AsyncRAT‑infected hosting provider 1337 Services GmbH, which has connections to previously seized RDP rental services.
💡 Why It Matters
- · By bypassing MFA through token replay, the attack demonstrates a scalable method to subvert modern authentication, forcing organizations to rethink token‑validation and device‑registration safeguards.