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Description

This analytic is to detect a suspicious child process of MSBuild spawned by Windows Script Host - cscript or wscript. This behavior or event are commonly seen and used by malware or adversaries to execute malicious msbuild process using malicious script in the compromised host. During triage, review parallel processes and identify any file modifications. MSBuild may load a script from the same path without having command-line arguments.

  • Type: TTP
  • Product: Splunk Behavioral Analytics
  • Datamodel: Endpoint_Processes
  • Last Updated: 2022-03-03
  • Author: Michael Haag, Splunk
  • ID: 92886f1c-9b11-11ec-848a-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1127.001 MSBuild Defense Evasion
T1127 Trusted Developer Utilities Proxy Execution Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • PR.PT
  • DE.CM
CIS20
  • CIS 8
CVE
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| 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 AND parent_process_name IS NOT NULL 
| where (parent_process_name LIKE "%wscript.exe" OR parent_process_name LIKE "%cscript.exe%") AND process_name="msbuild.exe" 
| 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:

:information_source: windows_script_host_spawn_msbuild_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _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 datamodel in the Processes node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

False positives should be limited as developers do not spawn MSBuild via a WSH.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
80.0 80 100 An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest_device_id$ by user $dest_user_id$.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

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

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