Windows BITS Upload Activity
Description
This analytic detects explicit BITS upload configuration through BITSAdmin /Create or /Transfer with /Upload or /Upload-Reply, or PowerShell Start-BitsTransfer with -TransferType Upload or UploadReply. Adversaries can abuse BITS to send collected files to remote infrastructure.
Query · spl
| tstats `security_content_summariesonly`
count min(_time) as firstTime
max(_time) as lastTime
FROM datamodel=Endpoint.Processes WHERE
Processes.process="*upload*"
(
`process_bitsadmin`
OR
(
`process_powershell`
Processes.process="*Start-BitsTransfer*"
)
)
BY Processes.action Processes.dest Processes.original_file_name
Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
Processes.process Processes.process_exec Processes.process_guid
Processes.process_hash Processes.process_id Processes.process_integrity_level
Processes.process_name Processes.process_path Processes.user
Processes.user_id Processes.vendor_product
| `drop_dm_object_name(Processes)`
| where
(
(
lower(process_name)="bitsadmin.exe"
OR
lower(original_file_name)="bitsadmin.exe"
)
AND match(process, "(?i)(?:^|\s)/(?:create|transfer)\s")
AND match(process, "(?i)(?:^|\s)/upload(?:-reply)?(?![\w-])")
)
OR
(
(
lower(process_name) IN ("powershell.exe", "pwsh.exe", "powershell_ise.exe")
OR
lower(original_file_name) IN ("powershell.exe", "pwsh.dll", "powershell_ise.exe")
)
AND match(process, "(?i)\bStart-BitsTransfer\b")
AND match(process, "(?i)-TransferType\\s+[\"\\x27]?Upload(?:Reply)?(?:[\"\\x27\\s;]|$)")
)
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `windows_bits_upload_activity_filter`
Implementation guide
The detection is based on data that originates from Endpoint Detection and Response (EDR) agents.
These agents are designed to provide security-related telemetry from the endpoints where the agent is installed.
To implement this search, you must ingest logs that contain the process GUID, process name, and parent process.
Additionally, you must ingest complete command-line executions.
These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product.
The logs must also be mapped to the Processes node of the Endpoint data model.
Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
Known false positives
- Administrative support bundles, diagnostics, file publishing and authorized tests may explicitly upload files using BITS. Verify the job purpose and destination before tuning the filter macro. An upload command alone does not establish exfiltration.
Analyst notes
Known false positives: Administrative support bundles, diagnostics, file publishing and authorized tests may explicitly upload files using BITS. Verify the job purpose and destination before tuning the filter macro. An upload command alone does not establish exfiltration.