Name:O365 Email Transport Rule Changed id:11ebb7c2-46bd-41c9-81e1-d0b4b34583a2 version:7 date:None author:Steven Dick status:production type:Anomaly Description:The following analytic identifies when a user with sufficient access to Exchange Online alters the mail flow/transport rule configuration of the organization. Transport rules are a set of rules that can be used by attackers to modify or delete emails based on specific conditions, this activity could indicate an attacker hiding or exfiltrated data. Data_source:
-Office 365 Universal Audit Log
search:`o365_management_activity` Workload=Exchange AND Operation IN ("Set-*","Disable-*","New-*","Remove-*") AND Operation="*TransportRule" | eval object_name = case('Parameters{}.Name'=="Name",mvindex('Parameters{}.Value',mvfind('Parameters{}.Name',"^Name$")),true(),ObjectId), object_id = case('Parameters{}.Name'=="Identity",mvindex('Parameters{}.Value',mvfind('Parameters{}.Name',"^Identity$")),true(),Id) | stats values(object_name) as object_name, min(_time) as firstTime, max(_time) as lastTime, count by object_id, UserId, Operation, signature | rename UserId as user | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_email_transport_rule_changed_filter`
how_to_implement:You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. known_false_positives:Legitimate administrative changes for business needs. References: -https://attack.mitre.org/techniques/T1114/003/ -https://cardinalops.com/blog/cardinalops-contributes-new-mitre-attck-techniques-related-to-abuse-of-mail-transport-rules/ -https://www.microsoft.com/en-us/security/blog/2022/09/22/malicious-OAuth-applications-used-to-compromise-email-servers-and-spread-spam/ drilldown_searches: name:'View the detection results for - "$user$"' search:'%original_detection_search% | search user = "$user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'7d' latest_offset:'0' name:'Investigate changes by $user$' search:'`o365_management_activity` Workload=Exchange AND Operation IN ("Set-*","Disable-*","New-*","Remove-*") AND Operation="*Transport*" UserId=$user$' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' analytic_story:['Data Exfiltration', 'Office 365 Account Takeover']
