Name:O365 Email New Inbox Rule Created id:449f525a-7b42-47be-96a7-d9724e336c19 version:1 date:2025-01-20 author:Steven Dick status:production type:Anomaly Description:The following analytic identifies the creation of new email inbox rules in an Office 365 environment. It detects events logged under New-InboxRule and Set-InboxRule operations within the o365_management_activity data source, focusing on parameters that may indicate mail forwarding, removal, or obfuscation. Inbox rule creation is a typical end-user activity however attackers also leverage this technique for multiple reasons. Data_source:
-Office 365 Universal Audit Log
search:`o365_management_activity` Workload=Exchange AND (Operation=New-InboxRule OR Operation=Set-InboxRule) Parameters{}.Name IN (SoftDeleteMessage,DeleteMessage,ForwardTo,ForwardAsAttachmentTo,RedirectTo,MoveToFolder,CopyToFolder) | eval file_path = mvappend(MoveToFolder,CopyToFolder), recipient=mvappend(ForwardTo, ForwardAsAttachmentTo, RedirectTo), user = lower(UserId), signature = Operation, src = if(match(ClientIP, "^\["), ltrim(mvindex(split(ClientIP, "]:"), 0), "["), mvindex(split(ClientIP,":"),0)), desc = Name, action = 'Parameters{}.Name'
| stats values(action) as action, values(src) as src, values(recipient) as recipient, values(file_path) as file_path, count, min(_time) as firstTime, max(_time) as lastTime by user, signature, desc | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_email_new_inbox_rule_created_filter`
how_to_implement:You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. known_false_positives:Users may create email rules for legitimate purposes. Filter as needed. References: -https://attack.mitre.org/techniques/T1114/ -https://www.hhs.gov/sites/default/files/help-desk-social-engineering-sector-alert-tlpclear.pdf -https://intelligence.abnormalsecurity.com/attack-library/threat-actor-convincingly-impersonates-employee-requesting-direct-deposit-update-in-likely-ai-generated-attack 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 Inbox Rules for $user$' search:'`o365_management_activity` Workload=Exchange AND (Operation=New-InboxRule OR Operation=Set-InboxRule) AND UserId = "$user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Office 365 Collection Techniques' asset_type:O365 Tenant mitre_attack_id: - 'T1114.003' - 'T1564.008' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' security_domain:audit
