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Description

The following analytic identifies the Windows InstallUtil.exe binary making a remote network connection. This technique may be used to download and execute code while bypassing application control using the /u (uninstall) switch.
InstallUtil uses the functions install and uninstall within the System.Configuration.Install namespace to process .net assembly. Install function requires admin privileges, however, uninstall function can be run as an unprivileged user.
When InstallUtil.exe is used in a malicous manner, the path to an executable on the filesystem is typically specified. Take note of the parent process. In a suspicious instance, this will be spawned from a non-standard process like Cmd.exe, PowerShell.exe or Explorer.exe.
If used by a developer, typically this will be found with multiple command-line switches/arguments and spawn from Visual Studio.
During triage review resulting network connections, file modifications, and parallel processes. Capture any artifacts and review further.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-11-12
  • Author: Michael Haag, Splunk
  • ID: 1a52c836-43ef-11ec-a36c-acde48001122

ATT&CK

ID Technique Tactic
T1218.004 InstallUtil Defense Evasion
T1218 Signed Binary Proxy Execution Defense Evasion

| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where `process_installutil` Processes.process IN ("*/u*", "*uninstall*") by _time span=1h  Processes.process_guid 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)` 
| 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 original_file_name process_path process process_guid connection_to_CNC dest_port 
| `windows_installutil_uninstall_option_with_network_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 and Ports 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
  • Ports.process_guid
  • Ports.dest
  • Ports.dest_port

Kill Chain Phase

  • Exploitation
  • Privilege Escalation

Known False Positives

Limited false positives should be present as InstallUtil is not typically used to download remote files. Filter as needed based on Developers requirements.

RBA

Risk Score Impact Confidence Message
80.0 80 100 An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ performing an uninstall.

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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