LoFP / users and administrators can create inbox rules for legitimate purposes. verify if it complies with the company policy and done with the user's consent. exceptions can be added to this rule to filter expected behavior.

Techniques

• T1114

Sample rules

Microsoft 365 Inbox Forwarding Rule Created

• source: elastic
• technicques:
  • T1114

Description

Identifies when a new Inbox forwarding rule is created in Microsoft 365. Inbox rules process messages in the Inbox based on conditions and take actions. In this case, the rules will forward the emails to a defined address. Attackers can abuse Inbox Rules to intercept and exfiltrate email data without making organization-wide configuration changes or having the corresponding privileges.

Detection logic

event.dataset:o365.audit and event.provider:Exchange and
event.category:web and event.action:("New-InboxRule" or "Set-InboxRule") and
    (
        o365.audit.Parameters.ForwardTo:* or
        o365.audit.Parameters.ForwardAsAttachmentTo:* or
        o365.audit.Parameters.RedirectTo:*
    )
    and event.outcome:success