BEC Email Forwarding Rule to External Domain Outside Business Hours
This rule detects the creation or modification of inbox rules in Office 365 that involve email forwarding or redirection to external domains. It calculates a risk score based on whether the action occurred outside of typical business hours (08:00-18:00 local time/weekends) and whether the user is performing this action from a previously unseen IP address, which may indicate a compromised account attempting to exfiltrate or redirect emails.
Splunk (SPL)

