Try in Splunk Security Cloud

Description

The following analytic identifies rundll32.exe with no command line arguments. 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, identify 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
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-09-20
  • Author: Michael Haag, Splunk
  • ID: e451bd16-e4c5-4109-8eb1-c4c6ecf048b4

ATT&CK

ID Technique Tactic
T1218 Signed Binary Proxy Execution Defense Evasion
T1218.011 Rundll32 Defense Evasion

| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where `process_rundll32` by _time span=1h  Processes.process_id Processes.process_name Processes.dest Processes.process_path Processes.process Processes.parent_process_name 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| regex process="(rundll32\.exe.{0,4}$)" 
| `suspicious_rundll32_no_command_line_arguments_filter`

Associated Analytic Story

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.

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

Kill Chain Phase

  • Actions on Objectives

Known False Positives

Although unlikely, some legitimate applications may use a moved copy of rundll32, triggering a false positive.

RBA

Risk Score Impact Confidence Message
49.0 70 70 Suspicious rundll32.exe process with no command line arguments executed on $dest$ by $user$

CVE

ID Summary CVSS
CVE-2021-34527 Windows Print Spooler Remote Code Execution Vulnerability 9.0

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

source | version: 2