Nterl0k - T1114.003 O365 Transport Rule Changed

detections/cloud/o365_email_transport_rule_changed.yml

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+name: O365 Email Transport Rule Changed
+id: 11ebb7c2-46bd-41c9-81e1-d0b4b34583a2
+version: 1
+date: '2025-01-15'
+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
+  | rename UserId as user, Operation as signature
+  | `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 ("$user$") starthoursago=168  | 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: $info_min_time$
+  latest_offset: $info_max_time$
+- 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: $info_max_time$
+rba:
+  message: The user [$user$] altered the exchange transport rule id $object_id$ [$object_name$]
+  risk_objects:
+  - field: user
+    type: user
+    score: 25
+  threat_objects:
+  - field: object_id
+    type: signature
+  - field: object_name
+    type: signature   
+tags:
+  analytic_story: 
+  - Data Exfiltration
+  - Office 365 Account Takeover
+  asset_type: O365 Tenant 
+  mitre_attack_id: 
+  - T1114.003
+  - T1564.008
+  product: 
+  - Splunk Enterprise
+  - Splunk Enterprise Security
+  - Splunk Cloud
+  security_domain: threat
+tests:
+- name: True Positive Test
+  attack_data:
+  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1114.003/transport_rule_change/transport_rule_change.log
+    source: o365
+    sourcetype: o365:management:activity