Multiple users email forwarded to same destination
This query over Office Activity audit data highlights cases where user mail is being forwarded. Identifies when multiple user mailboxes are configured to forward to the same destination.
This could be an attacker-controlled destination mailbox configured to collect mail from multiple compromised user accounts.
MITRE ATT&CK Tactics
Group policy change affecting multiple users email accounts
1. Review the affected O365 email accounts and destination email address.
2. Understand if this is a legitimate configuration within organization
3. Review SENT email content to understand if any attachments (confidential data) was sent out of organization.
4. Evaluate if destination email address is on any Threat Intelligence list.
5. Remove forwarder from Office 365 Admin Exchange