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Merge pull request #3298 from nterl0k/nterl0k-t1567-o365-sus-file-exfil
Nterl0k - T1567 - Suspect File Exfiltration Behaviors
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‎detections/cloud/o365_exfiltration_via_file_access.yml‎

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name: O365 Exfiltration via File Access
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id: 80b44ae2-60ff-43f1-8e56-34beb49a340a
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version: 1
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date: '2024-10-14'
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author: Steven Dick
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status: production
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type: Anomaly
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description: The following analytic detects when an excessive number of files are access from o365 by the same user over a short period of time. A malicious actor may abuse the "open in app" functionality of SharePoint through scripted or Graph API based access to evade triggering the FileDownloaded Event. This behavior may indicate an attacker staging data for exfiltration or an insider threat removing organizational data. Additional attention should be take with any Azure Guest (#EXT#) accounts.
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data_source:
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- Office 365 Universal Audit Log
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search: |-
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`o365_management_activity` Operation IN ("fileaccessed") UserId!=app@sharepoint NOT SourceFileExtension IN (bmp,png,jpeg,jpg)
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| eval user = replace(mvindex(split(lower(UserId),"#ext#"),0),"_","@"), user_flat = replace(UserId, "[^A-Za-z0-9]","_")
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| where NOT match(SiteUrl,user_flat)
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| stats values(user) as user, latest(ClientIP) as src values(ZipFileName) as file_name, values(Operation) as signature, values(UserAgent) as http_user_agent, dc(SourceFileName) as count, min(_time) as firstTime, max(_time) as lastTime by Workload,UserId,SiteUrl
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| eventstats avg(count) as avg stdev(count) as stdev by Workload
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| rename SiteUrl as file_path,Workload as app
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| where count > 50 AND count > (avg + (3*(stdev)))
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| `security_content_ctime(firstTime)`
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| `security_content_ctime(lastTime)`
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| `o365_exfiltration_via_file_access_filter`
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how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
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known_false_positives: It is possible that certain file access scenarios may trigger this alert, specifically OneDrive syncing and users accessing personal onedrives of other users. Adjust threshold and filtering as needed.
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references:
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- https://attack.mitre.org/techniques/T1567/exfil
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- https://www.varonis.com/blog/sidestepping-detection-while-exfiltrating-sharepoint-data
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- https://thedfirjournal.com/posts/m365-data-exfiltration-rclone/
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drilldown_searches:
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- name: View the detection results for - "$user$"
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search: '%original_detection_search% | search user = "$user$"'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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- name: View risk events for the last 7 days for - "$user$"
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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)`'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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- name: Investigate file access by $user$
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search: '`o365_management_activity` Operation IN ("fileaccessed") UserId="$UserId$"'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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rba:
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message: The user $user$ accessed an excessive number of files [$count$] from $file_path$ using $src$
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risk_objects:
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- field: user
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type: user
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score: 20
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threat_objects:
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- field: src
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type: ip_address
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tags:
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analytic_story:
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- Data Exfiltration
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- Office 365 Account Takeover
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asset_type: O365 Tenant
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mitre_attack_id:
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- T1567
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- T1530
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product:
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- Splunk Enterprise
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- Splunk Enterprise Security
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- Splunk Cloud
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security_domain: threat
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tests:
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- name: True Positive Test
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attack_data:
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- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1567/o365_sus_file_activity/o365_sus_file_activity.log
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source: o365
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sourcetype: o365:management:activity

‎detections/cloud/o365_exfiltration_via_file_download.yml‎

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name: O365 Exfiltration via File Download
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id: 06b23921-bfe2-4576-89dd-616f06e129da
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version: 1
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date: '2024-10-14'
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author: Steven Dick
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status: production
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type: Anomaly
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description: The following analytic detects when an excessive number of files are downloaded from o365 by the same user over a short period of time. O365 may bundle these files together as a ZIP file, however each file will have it's own download event. This behavior may indicate an attacker staging data for exfiltration or an insider threat removing organizational data. Additional attention should be taken with any Azure Guest (#EXT#) accounts.
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data_source:
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- Office 365 Universal Audit Log
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search: |-
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`o365_management_activity` Operation IN ("filedownloaded")
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| eval user = replace(mvindex(split(lower(UserId),"#ext#"),0),"_","@"), user_flat = replace(UserId, "[^A-Za-z0-9]","_")
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| stats values(user) as user, latest(ClientIP) as src values(ZipFileName) as file_name, values(Operation) as signature, values(UserAgent) as http_user_agent, dc(SourceFileName) as count, min(_time) as firstTime, max(_time) as lastTime by Workload,UserId,SiteUrl
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| rename SiteUrl as file_path,Workload as app
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| where count > 50
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| `security_content_ctime(firstTime)`
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| `security_content_ctime(lastTime)`
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| `o365_exfiltration_via_file_download_filter`
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how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
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known_false_positives: It is possible that certain file download scenarios may trigger this alert, specifically OneDrive syncing. Adjust threshold and filtering as needed.
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references:
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- https://attack.mitre.org/techniques/T1567/exfil
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- https://www.varonis.com/blog/sidestepping-detection-while-exfiltrating-sharepoint-data
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- https://thedfirjournal.com/posts/m365-data-exfiltration-rclone/
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drilldown_searches:
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- name: View the detection results for - "$user$"
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search: '%original_detection_search% | search user = "$user$"'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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- name: View risk events for the last 7 days for - "$user$"
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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)`'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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- name: Investigate file downloads by $user$
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search: '`o365_management_activity` Operation IN ("filedownloaded") UserId="$UserId$"'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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rba:
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message: The user $user$ downloaded an excessive number of files [$count$] from $file_path$ using $src$
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risk_objects:
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- field: user
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type: user
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score: 25
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threat_objects:
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- field: src
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type: ip_address
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tags:
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analytic_story:
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- Data Exfiltration
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- Office 365 Account Takeover
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asset_type: O365 Tenant
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mitre_attack_id:
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- T1567
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- T1530
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product:
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- Splunk Enterprise
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- Splunk Enterprise Security
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- Splunk Cloud
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security_domain: threat
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tests:
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- name: True Positive Test
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attack_data:
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- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1567/o365_sus_file_activity/o365_sus_file_activity.log
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source: o365
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sourcetype: o365:management:activity

‎detections/cloud/o365_exfiltration_via_file_sync_download.yml‎

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name: O365 Exfiltration via File Sync Download
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id: 350837b5-13d3-4c06-b688-db07afbe5050
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version: 1
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date: '2024-10-14'
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author: Steven Dick
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status: production
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type: Anomaly
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description: The following analytic detects when an excessive number of files are sync from o365 by the same user over a short period of time. A malicious actor abuse the user-agent string through GUI or API access to evade triggering the FileDownloaded event. This behavior may indicate an attacker staging data for exfiltration or an insider threat removing organizational data. Additional attention should be taken with any Azure Guest (#EXT#) accounts.
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data_source:
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- Office 365 Universal Audit Log
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search: |-
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`o365_management_activity` Operation IN ("filesyncdownload*") UserAgent="*SkyDriveSync*"
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| eval user = replace(mvindex(split(lower(UserId),"#ext#"),0),"_","@"), user_flat = replace(UserId, "[^A-Za-z0-9]","_")
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| where NOT match(SiteUrl,user_flat)
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| stats values(user) as user, latest(ClientIP) as src values(ZipFileName) as file_name, values(Operation) as signature, values(UserAgent) as http_user_agent, dc(SourceFileName) as count, min(_time) as firstTime, max(_time) as lastTime by Workload,UserId,SiteUrl
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| rename SiteUrl as file_path,Workload as app
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| where count > 50
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| `security_content_ctime(firstTime)`
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| `security_content_ctime(lastTime)`
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| `o365_exfiltration_via_file_sync_download_filter`
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how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
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known_false_positives: It is possible that certain file sync scenarios may trigger this alert, specifically OneNote. Adjust threshold and filtering as needed.
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references:
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- https://attack.mitre.org/techniques/T1567/exfil
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- https://www.varonis.com/blog/sidestepping-detection-while-exfiltrating-sharepoint-data
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- https://thedfirjournal.com/posts/m365-data-exfiltration-rclone/
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drilldown_searches:
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- name: View the detection results for - "$user$"
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search: '%original_detection_search% | search user = "$user$"'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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- name: View risk events for the last 7 days for - "$user$"
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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)`'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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- name: Investigate file sync downloads by $user$
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search: '`o365_management_activity` Operation IN ("filesyncdownload*") UserId="$UserId$"'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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rba:
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message: The user $user$ synced an excessive number of files [$count$] from $file_path$ using $src$
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risk_objects:
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- field: user
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type: user
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score: 25
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threat_objects:
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- field: src
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type: ip_address
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tags:
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analytic_story:
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- Data Exfiltration
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- Office 365 Account Takeover
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asset_type: O365 Tenant
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mitre_attack_id:
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- T1567
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- T1530
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product:
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- Splunk Enterprise
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- Splunk Enterprise Security
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- Splunk Cloud
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security_domain: threat
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tests:
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- name: True Positive Test
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attack_data:
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- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1567/o365_sus_file_activity/o365_sus_file_activity.log
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source: o365
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sourcetype: o365:management:activity

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