Anomalous Third-Party Vendor Guest Account or API Activity

Ankit Mehta@Secvyn

•updated Sep 9, 2026•1•0•3

This rule detects anomalous activity involving guest users (external identities) or service principals in Azure AD (Microsoft Entra ID). It baselines typical behavior—including IP addresses, countries, and sign-in frequency—over a 14-day period and alerts when activity in the last 24 hours deviates significantly. This includes sign-ins from new IP addresses or countries, sudden spikes in sign-in volume, after-hours access, or failed authentication attempts, which may indicate account takeover or misuse of third-party vendor access.