Malicious Inbox Rule Hiding Security Mail to RSS Feeds via M365 (via m365)

ATT&CK techniques

Defense Evasion → Collection

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1564.008Email Hiding Rules
Cred Access
Discovery
Lateral Movement
Collection
- T1114.003Email Forwarding Rule
C2
Exfiltration
Impact

What it detects

This rule detects creation of an Exchange Online inbox rule that moves messages into the RSS Feeds folder and marks them as read. This is a common business email compromise technique to hide security notifications and replies from the compromised user. Concealing warning mail lets the attacker operate the mailbox and pursue fraud undetected.

Reporting behind it

Related detections9 linkedT1114.003 — drag to rearrange

Malicious Exchange Inbox Rule Hiding Direct Deposit and Bank Emails via Payroll Pirate Compromise (via m365)

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Windows PowerShell: New-InboxRule/Set-InboxRule Script Block Activity

Microsoft 365 Audit Logs: Inbox Rule Creation or Update with Email Hiding Actions

O365 Mail Forwarding and Redirecting Rule Changes

Suspicious Inbox Rule Hiding Mail to Deleted Items via M365 Exchange

Suspicious Mailbox Forwarding Rule Creation Following AiTM Phishing

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

Suspicious Inbox Rule Creation With Forwarding or Deletion via M365 Exchange

Malicious Inbox Rule Hiding Security Mail to RSS Feeds via M365 (via m365)

Pivot detection · T1114.003 · 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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