Detection: Control Loading from World Writable Directory

Description

The following analytic identifies instances of control.exe loading a .cpl or .inf file from a writable directory, which is related to CVE-2021-40444. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line executions mapped to the Processes node of the Endpoint data model. This activity is significant as it may indicate an attempt to exploit a known vulnerability, potentially leading to unauthorized code execution. If confirmed malicious, this could allow an attacker to gain control over the affected system, leading to further compromise.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where (Processes.process_name=control.exe OR Processes.original_file_name=CONTROL.EXE) AND Processes.process IN ("*\\appdata\\*", "*\\windows\\temp\\*", "*\\programdata\\*") by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.original_file_name 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `control_loading_from_world_writable_directory_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	N/A	'crowdstrike:events:sensor'	'crowdstrike'
Sysmon EventID 1	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688	Windows	'xmlwineventlog'	'XmlWinEventLog:Security'

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 will be present as control.exe does not natively load from writable paths as defined. One may add .cpl or .inf to the command-line if there is any false positives. Tune as needed.

Associated Analytic Story

• Living Off The Land

• Microsoft MSHTML Remote Code Execution CVE-2021-40444

Risk Based Analytics (RBA)

References

• https://strontic.github.io/xcyclopedia/library/rundll32.exe-111474C61232202B5B588D2B512CBB25.html

• https://app.any.run/tasks/36c14029-9df8-439c-bba0-45f2643b0c70/

• https://attack.mitre.org/techniques/T1218/011/

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444

• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.002/T1218.002.yaml

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: 4