Suspicious Legacy Authentication via BAV2ROPC User Agent (via m365)

ATT&CK techniques

Initial Access → Defense Evasion

Recon
Resource Dev
Initial Access
- T1078.004Cloud Accounts
Execution
Persistence
- T1078.004Cloud Accounts
Priv Esc
- T1078.004Cloud Accounts
Defense Evasion
- T1078.004Cloud Accounts
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects Entra ID sign-ins using the BAV2ROPC user agent that indicates legacy resource owner password credential authentication over IMAP or SMTP. Threat actors abusing OAuth applications used this legacy flow to bypass modern authentication controls for mailbox access.

Reporting behind it

Related detections9 linkedT1078.004 — drag to rearrange

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Suspicious Legacy Authentication via BAV2ROPC User Agent (via m365)

Pivot detection · T1078.004 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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