Detection: Windows InstallUtil Remote Network Connection

Description

The following analytic detects the Windows InstallUtil.exe binary making a remote network connection. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process and network telemetry. This activity is significant because InstallUtil.exe can be exploited to download and execute malicious code, bypassing application control mechanisms. If confirmed malicious, an attacker could achieve code execution, potentially leading to further system compromise, data exfiltration, or lateral movement within the network. Analysts should review the parent process, network connections, and any associated file modifications to determine the legitimacy of this activity.

Search

 1
 2| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes
 3  where `process_installutil` by _time span=1h Processes.process_id Processes.process_name
 4  Processes.dest Processes.user Processes.process_path Processes.process Processes.parent_process_name
 5  Processes.original_file_name 
 6
 7| `drop_dm_object_name(Processes)` 
 8
 9| `security_content_ctime(firstTime)` 
10
11| `security_content_ctime(lastTime)` 
12
13| join process_id dest
14    [
15| tstats `security_content_summariesonly`
16        count FROM datamodel=Network_Traffic.All_Traffic where All_Traffic.dest_port !=
17        0 by All_Traffic.process_id All_Traffic.dest All_Traffic.dest_port All_Traffic.src
18    
19| `drop_dm_object_name(All_Traffic)` 
20    
21| rename dest as command_and_control
22    
23| rename src as dest] 
24
25| table _time user src dest parent_process_name process_name process_path process process_id dest_port command_and_control
26
27| stats count min(_time) as firstTime max(_time) as lastTime values(process) as process values(command_and_control) as command_and_control by user dest process_name process_id dest_port parent_process_name 
28
29| `security_content_ctime(firstTime)` 
30
31| `security_content_ctime(lastTime)`
32| `windows_installutil_remote_network_connection_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 1	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Sysmon EventID 3	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

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.

Associated Analytic Story

• Compromised Windows Host

• Living Off The Land

• Signed Binary Proxy Execution InstallUtil

Risk Based Analytics (RBA)

Risk Message:

An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ generating a remote download.

References

• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.004/T1218.004.md

Detection Testing

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: GitHub | Version: 11