Detect Hidden Users in IBM QRadar
Adversaries may use hidden users to hide the presence of user accounts they create or modify. On Windows, accounts can be hidden from the login screen by setting a registry value under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList with a DWORD value of 0 for the username. On macOS, adversaries can set a user's UID below 500 or set a UserShell property to /usr/bin/false to hide them. Threat actors including Dragonfly, Kimsuky, and SMOKEDHAM malware use hidden user accounts for persistent backdoor access.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1564 Hide Artifacts
- Sub-technique
- T1564.002 Hidden Users
- Canonical reference
- https://attack.mitre.org/techniques/T1564/002/
QRadar Detection Query
SELECT DATEFORMAT(starttime, 'yyyy-MM-dd HH:mm:ss') AS event_time,
sourceip, username, QIDNAME(qid) AS event_name,
"TargetObject", "Details", "Image", LOGSOURCENAME(logsourceid) AS log_source,
CATEGORYNAME(category) AS event_category
FROM events
WHERE LOGSOURCETYPEID(logsourceid) IN (143, 12, 433)
AND starttime > NOW() - 86400000
AND (
(QIDNAME(qid) LIKE '%Registry%' AND "TargetObject" LIKE '%SpecialAccounts%UserList%')
OR
("EventID" IN ('4720') )
OR
("EventID" IN ('4732') AND "Message" LIKE '%Administrators%')
OR
("CommandLine" LIKE '%net%user%/add%' OR "CommandLine" LIKE '%net1%user%/add%')
)
ORDER BY starttime DESC
LAST 24 HOURSDetects hidden user account creation via registry manipulation of SpecialAccounts\UserList, Windows Security events for user account creation (4720) and administrative group membership changes (4732), and net.exe command-line user addition.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate IT admin activity creating local accounts for shared workstations or kiosk systems that need to be hidden from login UI
- Domain join scripts or Group Policy preferences that add accounts and configure SpecialAccounts registry entries as part of standard desktop imaging
- Endpoint monitoring or backup agents that create local service accounts during installation using net.exe
Other platforms for T1564.002
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Create Hidden User Account via Registry
Expected signal: Windows Security Event ID 4720 (User Account Created) for HiddenTestUser. Sysmon Event ID 13 (Registry Value Set) for the SpecialAccounts key. Security Event ID 4688 for net.exe and reg.exe process creation.
- Test 2Create Hidden Admin User Account
Expected signal: Security Event ID 4720 (user created), 4732 (added to Administrators group), 4688 for net.exe x2 and reg.exe. Sysmon EventCode=13 for SpecialAccounts registry modification.
- Test 3Enumerate Hidden User Accounts
Expected signal: Security Event ID 4688 for reg.exe process creation. The query itself does not create events but identifies existing hidden accounts. No registry write events are generated.
References (4)
- https://attack.mitre.org/techniques/T1564/002/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1564.002/T1564.002.md
- https://docs.microsoft.com/en-us/windows/win32/secauthn/winlogon-and-credential-providers
- https://www.mandiant.com/resources/blog/smokedham-backdoor-delivers-cobalt-strike
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