Detection: Detect Renamed PSExec

Description

The following analytic identifies instances where PsExec.exe has been renamed and executed on an endpoint. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and original file names. This activity is significant because renaming PsExec.exe is a common tactic to evade detection. If confirmed malicious, this could allow an attacker to execute commands remotely, potentially leading to unauthorized access, lateral movement, or further compromise of the network.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where (Processes.process_name!=psexec.exe AND Processes.process_name!=psexec64.exe) AND Processes.original_file_name=psexec.c 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| `detect_renamed_psexec_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 should be present. It is possible some third party applications may use older versions of PsExec, filter as needed.

Associated Analytic Story

• Active Directory Lateral Movement

• BlackByte Ransomware

• CISA AA22-320A

• DHS Report TA18-074A

• DarkGate Malware

• DarkSide Ransomware

• HAFNIUM Group

• Rhysida Ransomware

• SamSam Ransomware

• Sandworm Tools

Risk Based Analytics (RBA)

References

• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1569.002/T1569.002.yaml

• https://redcanary.com/blog/threat-hunting-psexec-lateral-movement/

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: 8