Sunturai
Back to results
MediumElastic detection rulesElastic

Entra ID User Sign-In via Unusual Legacy Authentication Client

Detects a successful sign-in by a Member user principal through a legacy authentication client (such as Authenticated SMTP, IMAP4, POP3, Exchange ActiveSync, Exchange Web Services, or other basic-authentication…

Description

Detects a successful sign-in by a Member user principal through a legacy authentication client (such as Authenticated SMTP, IMAP4, POP3, Exchange ActiveSync, Exchange Web Services, or other basic-authentication clients) in Microsoft Entra ID, where the user principal has not been seen using a legacy client in the last 7 days. Legacy authentication clients rely on basic authentication, do not support modern authentication or interactive multi-factor authentication, and are frequently abused by adversaries for password spraying and account takeover because they translate into single-factor Resource Owner Password Credentials (ROPC) grants. This is a New Terms rule that surfaces the first occurrence of legacy client authentication for a given user, which is unusual in most modern environments.

Detection logic

Its licence does not clear it for publishing here

Sunturai publishes a detection's own text where the licence it arrived under has been reviewed and permits it, and Elastic License 2.0 has not. The query as its source wrote it, its canonical form and the hash that pins this revision are in the workspace record.

Sign in to read itCreate an account

Detection requirements

Platform
ContainersESXiIaaSIdentity ProviderLinuxmacOSNetwork DevicesOffice SuiteSaaSWindows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
event_index

Detections can measure how the public catalogue is used — which detections people look for, and which pages bring them here. It sets a cookie that recognises this browser for 180 days. It is never linked to an account and never follows you to other sites. Privacy notice