Detection: Windows Disable Lock Workstation Feature Through Registry

Description

The following analytic detects a suspicious registry modification that disables the Lock Computer feature in Windows. It leverages data from the Endpoint.Registry data model, specifically monitoring changes to the registry path "*\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\DisableLockWorkstation" with a value of "0x00000001". This activity is significant because it prevents users from locking their screens, a tactic often used by malware, including ransomware, to maintain control over compromised systems. If confirmed malicious, this could allow attackers to sustain their presence and execute further malicious actions without user interruption.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Registry WHERE (Registry.registry_path= "*\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System\\DisableLockWorkstation" Registry.registry_value_data = "0x00000001") BY Registry.dest Registry.user Registry.registry_path Registry.registry_key_name Registry.registry_value_name Registry.registry_value_data Registry.process_guid 
3| `drop_dm_object_name(Registry)` 
4| where isnotnull(registry_value_data) 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `windows_disable_lock_workstation_feature_through_registry_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 12	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Sysmon EventID 13	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Annotations

Default Configuration

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

Implementation

To successfully implement this search, you need to be ingesting logs with the registry value name, registry path, and registry value data from your endpoints. If you are using Sysmon, you must have at least version 2.0 of the offical Sysmon TA. https://splunkbase.splunk.com/app/5709

Known False Positives

unknown

Associated Analytic Story

• Ransomware

• Windows Defense Evasion Tactics

• Windows Registry Abuse

Risk Based Analytics (RBA)

References

• https://www.bleepingcomputer.com/news/security/in-dev-ransomware-forces-you-do-to-survey-before-unlocking-computer/

• https://heimdalsecurity.com/blog/fatalrat-targets-telegram/

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: 6