Mail Forwarding/Redirecting Activity Via ExchangePowerShell Cmdlet

Detects email forwarding or redirecting activity via ExchangePowerShell Cmdlet

title: Mail Forwarding/Redirecting Activity Via ExchangePowerShell Cmdlet
id: 0c7686d5-c74e-4292-b224-2a08e956ebc4
related:
    - id: c726e007-2cd0-4a55-abfb-79730fbedee5
      type: similar
    - id: 15b7abbb-8b40-4d01-9ee2-b51994b1d474
      type: obsolete
status: experimental
description: Detects email forwarding or redirecting activity via ExchangePowerShell Cmdlet
references:
    - https://redcanary.com/blog/email-forwarding-rules/
    - https://github.com/PwC-IR/Business-Email-Compromise-Guide/blob/fe29ce06aef842efe4eb448c26bbe822bf5b895d/PwC-Business_Email_Compromise-Guide.pdf
author: Nasreddine Bencherchali (Nextron Systems), Marco Pedrinazzi (@pedrinazziM) (InTheCyber)
date: 2026-03-01
tags:
    - attack.collection
    - attack.stealth
    - attack.t1114.003
    - attack.t1564.008
    - attack.exfiltration
    - attack.t1020
    - detection.threat-hunting
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection_cmdlet:
        ScriptBlockText|contains:
            - 'New-InboxRule'
            - 'Set-InboxRule'
            - 'Set-Mailbox'
    selection_params:
        ScriptBlockText|contains:
            - 'ForwardAsAttachmentTo'
            - 'ForwardingAddress'
            - 'ForwardingSmtpAddress'
            - 'ForwardTo'
            - 'RedirectTo' # Also covers "RedirectToRecipients"
    condition: all of selection_*
falsepositives:
    - Legitimate mail forwarding rules created by users or administrators to forward email to designated internal or external recipients for business or operational purposes.
level: medium

• T1020Automated Exfiltration
• T1114.003Email Forwarding Rule
• T1564.008Email Hiding Rules

• https://redcanary.com/blog/email-forwarding-rules/↗
• https://github.com/PwC-IR/Business-Email-Compromise-Guide/blob/fe29ce06aef842efe4eb448c26bbe822bf5b895d/PwC-Business_Email_Compromise-Guide.pdf↗