Detection: Windows Access Token Winlogon Duplicate Handle In Uncommon Path

Updated Date: 2024-08-15 ID: b8f7ed6b-0556-4c84-bffd-839c262b0278 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects a process attempting to duplicate the handle of winlogon.exe from an uncommon or public source path. This is identified using Sysmon EventCode 10, focusing on processes targeting winlogon.exe with specific access rights and excluding common system paths. This activity is significant because it may indicate an adversary trying to escalate privileges by leveraging the high-privilege tokens associated with winlogon.exe. If confirmed malicious, this could allow the attacker to gain elevated access, potentially leading to full system compromise and persistent control over the affected host.

Search

1`sysmon` EventCode=10  TargetImage IN("*\\system32\\winlogon.exe*", "*\\SysWOW64\\winlogon.exe*") AND GrantedAccess = 0x1040 AND NOT (SourceImage IN("C:\\Windows\\*", "C:\\Program File*", "%systemroot%\\*")) 
2| stats count min(_time) as firstTime max(_time) as lastTime by Computer SourceImage TargetImage SourceProcessGUID TargetProcessGUID SourceProcessId TargetProcessId GrantedAccess CallTrace 
3| rename Computer as dest
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_access_token_winlogon_duplicate_handle_in_uncommon_path_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Sysmon EventID 10	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_access_token_winlogon_duplicate_handle_in_uncommon_path_filter	`search *`

windows_access_token_winlogon_duplicate_handle_in_uncommon_path_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
T1134.001	Token Impersonation/Theft	Defense Evasion
T1134	Access Token Manipulation	Privilege Escalation

KillChainPhase.EXPLOITAITON

NistCategory.DE_AE

Cis18Value.CIS_10

APT28

FIN8

Blue Mockingbird

FIN6

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 Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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

Brute Ratel C4

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
A process $SourceImage$ is duplicating the handle token of winlogon.exe on $dest$	49	70	70

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: 3