splunk-security_content/docs/_posts/2022-02-16-windows_powershell_start-bitstransfer.md

title, excerpt, categories, last_modified_at, toc, toc_label, tags

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Windows PowerShell Start-BitsTransfer	BITS Jobs, Ingress Tool Transfer	Endpoint	2022-02-16	true		BITS Jobs Defense Evasion Persistence Ingress Tool Transfer Command & Control Splunk Behavioral Analytics Endpoint_Processes

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Description

Start-BitsTransfer is the PowerShell "version" of BitsAdmin.exe. Similar functionality is present. This technique variation is not as commonly used by adversaries, but has been abused in the past. Lesser known uses include the ability to set the -TransferType to Upload for exfiltration of files. In an instance where Upload is used, it is highly possible files will be archived. During triage, review parallel processes and process lineage. Capture any files on disk and review. For the remote domain or IP, what is the reputation?

• Type: TTP
• Product: Splunk Behavioral Analytics
• Datamodel: Endpoint_Processes
• Last Updated: 2022-02-16
• Author: Michael Haag, Splunk
• ID: 0bafd086-8f61-11ec-996e-acde48001122

ATT&CK

ID	Technique	Tactic
T1197	BITS Jobs	Defense Evasion, Persistence

| T1105 | Ingress Tool Transfer | Command And Control |

Search

| from read_ssa_enriched_events() 
| eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)), cmd_line=lower(ucast(map_get(input_event, "process"), "string", null)), process_name=lower(ucast(map_get(input_event, "process_name"), "string", null)), process_path=ucast(map_get(input_event, "process_path"), "string", null), parent_process_name=ucast(map_get(input_event, "parent_process_name"), "string", null), event_id=ucast(map_get(input_event, "event_id"), "string", null) 
| where cmd_line IS NOT NULL AND process_name IS NOT NULL 
| where process_name="pwsh.exe" OR process_name="pwsh.exe" OR process_name="sqlps.exe" OR process_name="sqltoolsps.exe" OR process_name="powershell.exe" OR process_name="powershell_ise.exe" 
| where (like (cmd_line, "%start-bitstransfer%")) 
| eval start_time=timestamp, end_time=timestamp, entities=mvappend(ucast(map_get(input_event, "dest_user_id"), "string", null), ucast(map_get(input_event, "dest_device_id"), "string", null)), body=create_map(["event_id", event_id, "cmd_line", cmd_line, "process_name", process_name, "parent_process_name", parent_process_name, "process_path", process_path]) 
| into write_ssa_detected_events();

Macros

The SPL above uses the following Macros:

Note that windows_powershell_start-bitstransfer_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

• _time
• dest_device_id
• process_name
• parent_process_name
• process_path
• dest_user_id
• process
• cmd_line

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint_Processess datamodel.

Known False Positives

Limited false positives. It is possible administrators will utilize Start-BitsTransfer for administrative tasks, otherwise filter based parent process or command-line arguments.

Associated Analytic story

• BITS Jobs
• Living Off The Land

Kill Chain Phase

• Exploitation

RBA

Risk Score	Impact	Confidence	Message
49.0	70	70	An instance of parent_process_name spawning process_name was identified on endpoint dest by user dest_user_id attempting to download a file.

Note that risk score is calculated base on the following formula: (Impact * Confidence)/100

Reference

• https://isc.sans.edu/diary/Investigating+Microsoft+BITS+Activity/23281
• https://docs.microsoft.com/en-us/windows/win32/bits/using-windows-powershell-to-create-bits-transfer-jobs

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1197/atomic_red_team/T1197_windows-security.log

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