Suspicious Exchange Online Mail Flow Rule or Connector Creation via Compromised Account

ATT&CK techniques

Persistence → Collection

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1098.005Device Registration
Priv Esc
- T1098.005Device Registration
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
- T1114.002Remote Email Collection
C2
Exfiltration
Impact

What it detects

This rule detects creation or modification of Exchange Online transport rules, inbound connectors, or DKIM signing configuration, matching post-compromise mailbox tampering observed in the Kali365 device code phishing ecosystem. Adversaries add mail flow rules and connectors to reroute, hide, or spoof mail after taking over an account. These mailbox-infrastructure changes support business email compromise and mass phishing distribution.

Reporting behind it

Related detections9 linkedT1098.005 — drag to rearrange

Possible Rogue Device Registration in Entra ID (via azure)

Suspicious Bulk Mail and File Collection via MSGraph Application Access (via m365)

Suspicious Token Request Using Microsoft Authentication Broker Client to Obtain Primary Refresh Token (via azure)

Suspicious Azure Tenant Root Elevation via elevateAccess

Suspicious Inbox Rule Hiding Mail to Deleted Items via M365 Exchange

Suspicious AWS Virtual MFA Device Creation

Malicious Exchange Mailbox Export to ASPX via New-MailboxExportRequest

Suspicious SCATTERED SPIDER Exchange Transport Rule Creation to Suppress Alerts (via m365)

Suspicious Device Registration Following OAuth Token Theft

Suspicious Exchange Online Mail Flow Rule or Connector Creation via Compromised Account

Pivot detection · T1098.005 · 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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