splunk-security_content/docs/_posts/2021-11-12-windows_installutil_uninstall_option.md

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title	excerpt	categories	last_modified_at	toc	toc_label	tags
Windows InstallUtil Uninstall Option	InstallUtil, Signed Binary Proxy Execution	Endpoint	2021-11-12	true		InstallUtil Defense Evasion Signed Binary Proxy Execution Defense Evasion Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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Description

The following analytic identifies the Windows InstallUtil.exe binary. This will 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: cfa7b9ac-43f0-11ec-9b48-acde48001122

ATT&CK

ID	Technique	Tactic
T1218.004	InstallUtil	Defense Evasion

| T1218 | Signed Binary Proxy Execution | Defense Evasion |

Search

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_installutil` Processes.process IN ("*/u*", "*uninstall*") by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.original_file_name Processes.process Processes.process_id Processes.parent_process_id 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_installutil_uninstall_option_filter`

Associated Analytic Story

• Signed Binary Proxy Execution InstallUtil

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

• Exploitation
• Privilege Escalation

Known False Positives

Limited false positives should be present. Filter as needed by parent process or application.

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

• https://evi1cg.me/archives/AppLocker_Bypass_Techniques.html#menu_index_12
• https://github.com/api0cradle/UltimateAppLockerByPassList/blob/master/md/Installutil.exe.md
• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.004/T1218.004.md

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/T1218.004/atomic_red_team/windows-sysmon.log

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