splunk-security_content/docs/_posts/2022-02-23-windows_mshta_child_process.md

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

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Windows MSHTA Child Process	Mshta, Signed Binary Proxy Execution	Endpoint	2022-02-23	true		Mshta Defense Evasion Signed Binary Proxy Execution Defense Evasion Splunk Behavioral Analytics Endpoint_Processes

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Description

The following analytic identifies child processes spawning from "mshta.exe". The search will return the first time and last time these command-line arguments were used for these executions, as well as the target system, the user, parent process "mshta.exe" and its child process.

• Type: TTP
• Product: Splunk Behavioral Analytics
• Datamodel: Endpoint_Processes
• Last Updated: 2022-02-23
• Author: Michael Haag, Splunk
• ID: f63f7e9c-9526-11ec-9fc7-acde48001122

ATT&CK

ID	Technique	Tactic
T1218.005	Mshta	Defense Evasion

| T1218 | Signed Binary Proxy Execution | Defense Evasion |

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 AND parent_process_name IS NOT NULL 
| where parent_process_name="mshta.exe" AND process_name="powershell.exe" OR process_name="cmd.exe" OR process_name="scrcons.exe" OR process_name="colorcpl.exe" OR process_name="msbuild.exe" OR process_name="microsoft.workflow.compiler.exe" OR process_name="searchprotocolhost.exe" OR process_name="cscript.exe"  OR process_name="wscript.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:

Note that windows_mshta_child_process_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 logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

Although unlikely, some legitimate applications may exhibit this behavior, triggering a false positive.

Associated Analytic story

• Suspicious MSHTA Activity
• Living Off The Land

Kill Chain Phase

• Exploitation

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 attempting to access a remote destination to download an additional payload.

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

Reference

• https://github.com/redcanaryco/AtomicTestHarnesses
• https://redcanary.com/blog/introducing-atomictestharnesses/

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/T1218.005/atomic_red_team/windows-security.log

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