Suspicious M365 Legacy Authentication via BAV2ROPC Client via m365

ATT&CK techniques

Initial Access → Lateral Movement

Recon
Resource Dev
Initial Access
- T1078.004Cloud Accounts
Execution
Persistence
- T1078.004Cloud Accounts
Priv Esc
- T1078.004Cloud Accounts
Defense Evasion
- T1078.004Cloud Accounts
- T1550.001Application Access Token
Cred Access
Discovery
Lateral Movement
- T1550.001Application Access Token
Collection
C2
Exfiltration
Impact

What it detects

This rule detects non-interactive Microsoft 365 sign-ins using the BAV2ROPC legacy authentication client. In the Railway PaaS token replay campaign, operators used BAV2ROPC to silently refresh stolen tokens and access mailboxes without triggering interactive MFA, so this client string on sign-ins indicates likely token abuse and legacy protocol exploitation.

Reporting behind it

Related detections9 linkedT1550.001 — drag to rearrange

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Suspicious M365 Legacy Authentication via BAV2ROPC Client via m365

Pivot detection · T1550.001 · 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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