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Description

The following analytic detects suspicious PowerShell processes attempting to inject code into critical Windows processes using CreateRemoteThread. It leverages Sysmon EventCode 8 to identify instances where PowerShell spawns threads in processes like svchost.exe, csrss.exe, and others. This activity is significant as it is commonly used by malware such as TrickBot and offensive tools like Cobalt Strike to execute malicious payloads, establish reverse shells, or download additional malware. If confirmed malicious, this behavior could lead to unauthorized code execution, privilege escalation, and persistent access within the environment.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-13
  • Author: Teoderick Contreras, Splunk
  • ID: ec102cb2-a0f5-11eb-9b38-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1055 Process Injection Defense Evasion, Privilege Escalation
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


1
2
3
4
5



`sysmon` EventCode = 8 parent_process_name IN ("powershell_ise.exe", "powershell.exe") TargetImage IN ("*\\svchost.exe","*\\csrss.exe" "*\\gpupdate.exe", "*\\explorer.exe","*\\services.exe","*\\winlogon.exe","*\\smss.exe","*\\wininit.exe","*\\userinit.exe","*\\spoolsv.exe","*\\taskhost.exe") 
| stats  min(_time) as firstTime max(_time) as lastTime count by SourceImage process_name SourceProcessId SourceProcessGuid TargetImage TargetProcessId NewThreadId StartAddress dest EventCode 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `powershell_remote_thread_to_known_windows_process_filter`

Macros

The SPL above uses the following Macros:

:information_source: powershell_remote_thread_to_known_windows_process_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • SourceImage
  • process_name
  • SourceProcessId
  • SourceProcessGuid
  • TargetImage
  • TargetProcessId
  • NewThreadId
  • StartAddress
  • dest
  • EventCode

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, Create Remote thread from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances of create remote thread may be used.

Known False Positives

unknown

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
63.0 70 90 A suspicious powershell process $process_name$ that tries to create a remote thread on target process $TargetImage$ with eventcode $EventCode$ in host $dest$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 3