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Description

The following analytic detects a process attempting to access winlogon.exe to duplicate its handle. This is identified using Sysmon EventCode 10, focusing on processes targeting winlogon.exe with specific access rights. This activity is significant because it is a common technique used by adversaries to escalate privileges by leveraging the high privileges and security tokens associated with winlogon.exe. If confirmed malicious, this could allow an attacker to gain elevated privileges, potentially leading to full system compromise and unauthorized access to sensitive information.

  • Type: Hunting

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

  • Last Updated: 2024-05-22
  • Author: Teoderick Contreras, Splunk
  • ID: dda126d7-1d99-4f0b-b72a-4c14031f9398

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1134.001 Token Impersonation/Theft Defense Evasion, Privilege Escalation
T1134 Access Token Manipulation Defense Evasion, Privilege Escalation
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`sysmon` EventCode=10 TargetImage IN("*\\system32\\winlogon.exe*", "*\\SysWOW64\\winlogon.exe*") GrantedAccess = 0x1040 
| stats count min(_time) as firstTime max(_time) as lastTime by SourceImage TargetImage SourceProcessGUID TargetProcessGUID SourceProcessId TargetProcessId GrantedAccess CallTrace dest user_id 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_access_token_manipulation_winlogon_duplicate_token_handle_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_access_token_manipulation_winlogon_duplicate_token_handle_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
  • TargetImage
  • SourceProcessGUID
  • TargetProcessGUID
  • SourceProcessId
  • TargetProcessId
  • GrantedAccess
  • CallTrace
  • dest
  • user_id

How To Implement

To successfully implement this search, you must be ingesting data that records process activity from your hosts to populate the endpoint data model in the processes node. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

It is possible legitimate applications will request access to winlogon, filter as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
36.0 60 60 A process $SourceImage$ is duplicating the handle token of winlogon.exe in $dest$

: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: 2