O365 Mailbox Email Forwarding Enabled
The following analytic identifies instances where email forwarding has been enabled on mailboxes within an Office 365 environment. It detects this activity by monitoring the Set-Mailbox operation within the…
Description
The following analytic identifies instances where email forwarding has been enabled on mailboxes within an Office 365 environment. It detects this activity by monitoring the Set-Mailbox operation within the o365_management_activity logs, specifically looking for changes to the ForwardingAddress or ForwardingSmtpAddress parameters. This activity is significant as unauthorized email forwarding can lead to data exfiltration and unauthorized access to sensitive information. If confirmed malicious, attackers could intercept and redirect emails, potentially compromising confidential communications and leading to data breaches.
Detection logic
Detection requirements
- Platform
- LinuxmacOSOffice SuiteWindows
The rule states no platform. This is derived from the ATT&CK technique it maps to.
Known benign triggers
- Email forwarding may be configured for legitimate purposes, filter as needed.
MITRE ATT&CK mappings
0 exclusive techniques.This is coverage no other published rule has; it is not this rule's total technique count.
References
| Reference | Cited by |
|---|---|
| attack.mitre.org/techniques/T1114/003/ | 4 |
| learn.microsoft.com/en-us/exchange/recipients/user-mailboxes/email-forwarding?view=exchserver-2019 | Only this detection cites it |
From the source
- At source
- Open at source
- Upstream identifier
- 0b6bc75c-05d1-4101-9fc3-97e706168f24
- Tagged by the source as
- Office 365 Collection TechniquesO365 TenantcloudSplunk CloudSplunk EnterpriseSplunk Enterprise Securitythreat
Licence
- Published under
- Apache License 2.0Read the licence
- Attribution
- Required
- Obtained under
- Apache-2.0Read the origin licence
Authorship
- Written by
- Published
- Aug 26, 2026
- Version
- 1