Name:O365 Email Suspicious Behavior Alert id:85c7555a-05af-4322-81aa-76b4ddf52baa version:2 date:2024-09-30 author:Steven Dick status:production type:TTP Description:The following analytic identifies when one of O365 the built-in security detections for suspicious email behaviors are triggered. These alerts often indicate that an attacker may have compromised a mailbox within the environment. Any detections from built-in Office 365 capabilities should be monitored and responded to appropriately. Certain premium Office 365 capabilities further enhance these detection and response functions. Data_source:
-O365 Universal Audit Log
search:`o365_management_activity` Workload=SecurityComplianceCenter Operation=AlertEntityGenerated Name IN ("Suspicious email sending patterns detected","User restricted from sending email","Suspicious Email Forwarding Activity","Email sending limit exceeded") | fromjson Data | stats count min(_time) as firstTime max(_time) as lastTime by AlertId,ObjectId,Operation,Name | rename Name as signature, AlertId as signature_id, ObjectId as user | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_email_suspicious_behavior_alert_filter`
how_to_implement:You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. The alerts must be enabled in the o365 security portal. known_false_positives:Users emailing for legitimate business purposes that appear suspicious. References: -https://learn.microsoft.com/en-us/purview/alert-policies 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:'$info_max_time$' tags: analytic_story: - 'Suspicious Emails' - 'Office 365 Collection Techniques' - 'Office 365 Account Takeover' asset_type:O365 Tenant confidence:100 impact:90 message:The user $user$ triggered the O365 security alert [$signature$] mitre_attack_id: - 'T1114' - 'T1114.003' observable: name:'user' type:'User' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'AlertId' - 'ObjectId' - 'Operation' - 'Name' - 'Workload' risk_score:90 security_domain:threat
