Detection: Suspicious Copy on System32

Description

The following analytic detects suspicious file copy operations from the System32 or SysWow64 directories, often indicative of malicious activity. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on processes initiated by command-line tools like cmd.exe or PowerShell. This behavior is significant as it may indicate an attempt to execute malicious code using legitimate system tools (LOLBIN). If confirmed malicious, this activity could allow an attacker to execute arbitrary code, potentially leading to system compromise or further lateral movement within the network.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name IN("cmd.exe", "powershell*","pwsh.exe", "sqlps.exe", "sqltoolsps.exe", "powershell_ise.exe") AND `process_copy` AND Processes.process IN("*\\Windows\\System32\\*", "*\\Windows\\SysWow64\\*") AND Processes.process = "*copy*" by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id temp 
3| `drop_dm_object_name(Processes)` 
4| eval splitted_commandline=split(process," ") 
5| eval first_cmdline=lower(mvindex(splitted_commandline,0)) 
6| where NOT LIKE(first_cmdline,"%\\windows\\system32\\%") AND NOT LIKE(first_cmdline,"%\\windows\\syswow64\\%") 
7| `security_content_ctime(firstTime)` 
8| `security_content_ctime(lastTime)` 
9|`suspicious_copy_on_system32_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

every user may do this event but very un-ussual.

Associated Analytic Story

• AsyncRAT

• Compromised Windows Host

• IcedID

• Qakbot

• Sandworm Tools

• Unusual Processes

• Volt Typhoon

Risk Based Analytics (RBA)

References

• https://www.hybrid-analysis.com/sample/8da5b75b6380a41eee3a399c43dfe0d99eeefaa1fd21027a07b1ecaa4cd96fdd?environmentId=120

• https://www.microsoft.com/en-us/security/blog/2023/05/24/volt-typhoon-targets-us-critical-infrastructure-with-living-off-the-land-techniques/

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