---
title: "Windows Rundll32 Inline HTA Execution"
excerpt: "Signed Binary Proxy Execution, Mshta"
categories:
  - Endpoint
last_modified_at: 2022-02-23
toc: true
toc_label: ""
tags:
  - Signed Binary Proxy Execution
  - Defense Evasion
  - Mshta
  - Defense Evasion
  - Splunk Behavioral Analytics
  - Endpoint_Processes
---



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#### Description

The following analytic identifies &#34;rundll32.exe&#34; execution with inline protocol handlers. &#34;JavaScript&#34;, &#34;VBScript&#34;, and &#34;About&#34; are the only supported options when invoking HTA content directly on the command-line. This type of behavior is commonly observed with fileless malware or application whitelisting bypass techniques. 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, process &#34;rundll32.exe&#34; and its parent process.

- **Type**: [TTP](https://github.com/splunk/security_content/wiki/Detection-Analytic-Types)
- **Product**: Splunk Behavioral Analytics
- **Datamodel**: [Endpoint_Processes](https://docs.splunk.com/Documentation/CIM/latest/User/EndpointProcesses)
- **Last Updated**: 2022-02-23
- **Author**: Michael Haag, Splunk
- **ID**: 0caa1dd6-94f5-11ec-9786-acde48001122


#### [ATT&CK](https://attack.mitre.org/)

| ID             | Technique        |  Tactic             |
| -------------- | ---------------- |-------------------- |
| [T1218](https://attack.mitre.org/techniques/T1218/) | Signed Binary Proxy Execution | Defense Evasion |

| [T1218.005](https://attack.mitre.org/techniques/T1218/005/) | Mshta | 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 
| where process_name="rundll32.exe" AND (like (cmd_line, "%vbscript%") OR like (cmd_line, "%javascript%") OR like (cmd_line, "%about%")) 
| 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_rundll32_inline_hta_execution_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` 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
Although unlikely, some legitimate applications may exhibit this behavior, triggering a false positive.

#### Associated Analytic story
* [Suspicious MSHTA Activity](/stories/suspicious_mshta_activity)
* [NOBELIUM Group](/stories/nobelium_group)
* [Living Off The Land](/stories/living_off_the_land)


#### Kill Chain Phase
* Exploitation



#### RBA

| Risk Score  | Impact      | Confidence   | Message      |
| ----------- | ----------- |--------------|--------------|
| 56.0 | 70 | 80 | Suspicious $process_name$ inline HTA execution on $dest_device_id$. |


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



#### Reference

* [https://github.com/redcanaryco/AtomicTestHarnesses](https://github.com/redcanaryco/AtomicTestHarnesses)
* [https://redcanary.com/blog/introducing-atomictestharnesses/](https://redcanary.com/blog/introducing-atomictestharnesses/)
* [https://docs.microsoft.com/en-us/windows/win32/search/-search-3x-wds-extidx-prot-implementing](https://docs.microsoft.com/en-us/windows/win32/search/-search-3x-wds-extidx-prot-implementing)



#### Test Dataset
Replay any dataset to Splunk Enterprise by using our [`replay.py`](https://github.com/splunk/attack_data#using-replaypy) tool or the [UI](https://github.com/splunk/attack_data#using-ui).
Alternatively you can replay a dataset into a [Splunk Attack Range](https://github.com/splunk/attack_range#replay-dumps-into-attack-range-splunk-server)

* [https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1218.005/atomic_red_team/windows-security.log](https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1218.005/atomic_red_team/windows-security.log)



[*source*](https://github.com/splunk/security_content/tree/develop/detections/endpoint/windows_rundll32_inline_hta_execution.yml) \| *version*: **1**