Detection: Suspicious Copy on System32

Updated Date: 2024-05-16 ID: ce633e56-25b2-11ec-9e76-acde48001122 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

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.

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 Supported App
CrowdStrike ProcessRollup2 N/A 'crowdstrike:events:sensor' 'crowdstrike' N/A

Macros Used

Name Value
process_copy (Processes.process_name=copy.exe OR Processes.original_file_name=copy.exe OR Processes.process_name=xcopy.exe OR Processes.original_file_name=xcopy.exe)
suspicious_copy_on_system32_filter search *
suspicious_copy_on_system32_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1036.003 Rename System Utilities Defense Evasion
T1036 Masquerading Defense Evasion
KillChainPhase.EXPLOITAITON
NistCategory.DE_CM
Cis18Value.CIS_10
APT32
GALLIUM
Lazarus Group
menuPass
APT28
APT32
BRONZE BUTLER
Dragonfly
FIN13
LazyScripter
Nomadic Octopus
OilRig
PLATINUM
Sandworm Team
TA551
TeamTNT
Windshift
ZIRCONIUM
menuPass

Default Configuration

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

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

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

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Execution of copy exe to copy file from $process$ in $dest$ 63 70 90
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational xmlwineventlog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational xmlwineventlog

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: 2