Abnormal successful Microsoft 365 Exchange login event
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Goal
Detect an Impossible Travel event by a user logging in to Microsoft Exchange.
Strategy
The Impossible Travel detection type’s algorithm compares the GeoIP data of the last and the current Microsoft-365 mailbox login event (@evt.name:MailboxLogin) to determine if the user {{@usr.name}} traveled more than 500km at over 1,000km/hr.
Triage and response
- Determine if
{{@usr.name}} should be connecting from {{@impossible_travel.triggering_locations.first_location.city}}, {{@impossible_travel.triggering_locations.first_location.country}} and {{@impossible_travel.triggering_locations.second_location.city}}, {{@impossible_travel.triggering_locations.second_location.country}} in a short period of time. - If the user should not be connecting from
{{@impossible_travel.triggering_locations.first_location.city}}, {{@impossible_travel.triggering_locations.first_location.country}} and {{@impossible_travel.triggering_locations.second_location.city}}, {{@impossible_travel.triggering_locations.second_location.country}}, then consider isolating the account and reset credentials. - Use the Cloud SIEM - User Investigation dashboard to audit any user actions that may have occurred after the illegitimate login.
Changelog
- 15 September 2025 - Excluded logins from corporate VPNs and service accounts to reduce false positives.
