---
title: "Rundll32 with no Command Line Arguments with Network"
excerpt: "Signed Binary Proxy Execution, Rundll32"
categories:
  - Endpoint
last_modified_at: 2021-10-13
toc: true
toc_label: ""
tags:
  - Signed Binary Proxy Execution
  - Defense Evasion
  - Rundll32
  - Defense Evasion
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  - CVE-2021-34527
  - Endpoint
---



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#### Description

The following analytic identifies rundll32.exe with no command line arguments and performing a network connection. It is unusual for rundll32.exe to execute with no command line arguments present. This particular behavior is common with malicious software, including Cobalt Strike. During investigation, triage any network connections and parallel processes. Identify any suspicious module loads related to credential dumping or file writes. Rundll32.exe is natively found in C:\Windows\system32 and C:\Windows\syswow64.

- **Type**: [TTP](https://github.com/splunk/security_content/wiki/Detection-Analytic-Types)
- **Product**: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- **Datamodel**: [Endpoint](https://docs.splunk.com/Documentation/CIM/latest/User/Endpoint)
- **Last Updated**: 2021-10-13
- **Author**: Michael Haag, Splunk
- **ID**: 35307032-a12d-11eb-835f-acde48001122


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

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

| [T1218.011](https://attack.mitre.org/techniques/T1218/011/) | Rundll32 | Defense Evasion |

#### Search

```

| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where `process_rundll32` by _time span=1h  Processes.process_guid Processes.process_name Processes.dest Processes.process_path Processes.process Processes.parent_process_name Processes.original_file_name 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| regex process="(rundll32\.exe.{0,4}$)" 
| join  process_guid [
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Ports where Ports.dest_port !="0" by Ports.process_guid Ports.dest Ports.dest_port
| `drop_dm_object_name(Ports)` 
| rename  dest as connection_to_CNC] 
| table _time dest parent_process_name process_name process_path process process_guid connection_to_CNC dest_port 
| `rundll32_with_no_command_line_arguments_with_network_filter`
```

#### Macros
The SPL above uses the following Macros:
* [process_rundll32](https://github.com/splunk/security_content/blob/develop/macros/process_rundll32.yml)
* [security_content_ctime](https://github.com/splunk/security_content/blob/develop/macros/security_content_ctime.yml)
* [security_content_summariesonly](https://github.com/splunk/security_content/blob/develop/macros/security_content_summariesonly.yml)

Note that `rundll32_with_no_command_line_arguments_with_network_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
* Processes.dest
* Processes.user
* Processes.parent_process_name
* Processes.parent_process
* Processes.original_file_name
* Processes.process_name
* Processes.process
* Processes.process_id
* Processes.parent_process_path
* Processes.process_path
* Processes.parent_process_id


#### 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` and `port` node. 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 use a moved copy of rundll32, triggering a false positive.

#### Associated Analytic story
* [Suspicious Rundll32 Activity](/stories/suspicious_rundll32_activity)
* [Cobalt Strike](/stories/cobalt_strike)
* [PrintNightmare CVE-2021-34527](/stories/printnightmare_cve-2021-34527)


#### Kill Chain Phase
* Exploitation



#### RBA

| Risk Score  | Impact      | Confidence   | Message      |
| ----------- | ----------- |--------------|--------------|
| 70.0 | 70 | 100 | A rundll32 process $process_name$ with no commandline argument like this process commandline $process$ in host $dest$ |


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


#### CVE

| ID          | Summary | [CVSS](https://nvd.nist.gov/vuln-metrics/cvss) |
| ----------- | ----------- | -------------- |
| [CVE-2021-34527](https://nvd.nist.gov/vuln/detail/CVE-2021-34527) | Windows Print Spooler Remote Code Execution Vulnerability | 9.0 |



#### Reference

* [https://attack.mitre.org/techniques/T1218/011/](https://attack.mitre.org/techniques/T1218/011/)
* [https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.011/T1218.011.md](https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.011/T1218.011.md)
* [https://lolbas-project.github.io/lolbas/Binaries/Rundll32](https://lolbas-project.github.io/lolbas/Binaries/Rundll32)
* [https://bohops.com/2018/02/26/leveraging-inf-sct-fetch-execute-techniques-for-bypass-evasion-persistence/](https://bohops.com/2018/02/26/leveraging-inf-sct-fetch-execute-techniques-for-bypass-evasion-persistence/)



#### 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/T1055/cobalt_strike/windows-sysmon.log](https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1055/cobalt_strike/windows-sysmon.log)



[*source*](https://github.com/splunk/security_content/tree/develop/detections/endpoint/rundll32_with_no_command_line_arguments_with_network.yml) \| *version*: **3**