Sign-in via Legacy Protocol (MFA/CA Bypass)
This rule detects successful sign-ins to Microsoft 365 services that occur via legacy authentication protocols. These protocols (e.g., Exchange ActiveSync, IMAP4, POP3, SMTP AUTH) do not support modern authentication methods like Multi-Factor Authentication (MFA) or Conditional Access policies, making them a potential bypass vector for adversaries who have compromised user credentials. The rule identifies the user, the specific legacy client application used, and provides details on the source IP address and country.
Microsoft Sentinel (KQL)
