Hiding User Account Via SpecialAccounts Registry Key

Hunt Hypothesis

Detects modifications to the registry key “HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\Userlist” where the value is set to “0” in order to hide user account from being l

Detection Rule

Sigma (Original)

title: Hiding User Account Via SpecialAccounts Registry Key
id: f8aebc67-a56d-4ec9-9fbe-7b0e8b7b4efd
related:
    - id: 8a58209c-7ae6-4027-afb0-307a78e4589a
      type: obsolete
    - id: 9ec9fb1b-e059-4489-9642-f270c207923d
      type: similar
status: test
description: Detects modifications to the registry key "HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\Userlist" where the value is set to "0" in order to hide user account from being listed on the logon screen.
references:
    - https://thedfirreport.com/2022/07/11/select-xmrig-from-sqlserver/
    - https://github.com/redcanaryco/atomic-red-team/blob/40b77d63808dd4f4eafb83949805636735a1fd15/atomics/T1564.002/T1564.002.md#atomic-test-3---create-hidden-user-in-registry
author: Nasreddine Bencherchali (Nextron Systems), frack113
date: 2022-07-12
modified: 2023-01-26
tags:
    - attack.stealth
    - attack.t1564.002
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|contains: '\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList'
        Details: 'DWORD (0x00000000)'
    condition: selection
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/registry/registry_set/registry_set_special_accounts/info.yml
simulation:
    - type: atomic-red-team
      name: Create Hidden User in Registry
      technique: T1564.002
      atomic_guid: 173126b7-afe4-45eb-8680-fa9f6400431c

KQL (Azure Sentinel)

imRegistry
| where RegistryKey contains "\\SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon\\SpecialAccounts\\UserList" and RegistryValueData =~ "DWORD (0x00000000)"

KQL (Microsoft 365 Defender)

DeviceRegistryEvents
| where RegistryKey contains "\\SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon\\SpecialAccounts\\UserList" and RegistryValueData =~ "DWORD (0x00000000)"

Required Data Sources

False Positive Guidance

• Unknown

MITRE ATT&CK Context

• Technique: T1564.002 — T1564.002

References

• https://thedfirreport.com/2022/07/11/select-xmrig-from-sqlserver/
• https://github.com/redcanaryco/atomic-red-team/blob/40b77d63808dd4f4eafb83949805636735a1fd15/atomics/T1564.002/T1564.002.md#atomic-test-3---create-hidden-user-in-registry
• SigmaHQ Rule