Payroll Pirate AiTM: Login:reprocess Error 50199 Followed by Cmsi:cmsi via Firefox 142.0
Detects a specific sign-in sequence indicative of a Payroll Pirate adversary-in-the-middle (AiTM) attack. The pattern involves a Microsoft Outlook interactive sign-in resulting in a 50199 error (Login:reprocess) followed within 10 minutes by a Cmsi:cmsi authentication attempt, both originating from the same user and the specific user-agent Firefox 142.0. This behavior is associated with 2FA proxying techniques where the attacker captures and replays session information.
Microsoft Sentinel (KQL)
