Registry Edit with Modification of Userinit, Shell or Notify

Hypothesis and description

Detection of modification of the registry key values of Notify, Userinit, and Shell located in HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\ and HKEY_LOCAL_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\. When a user logs on, the Registry key values of Notify, Userinit and Shell are used to load dedicated Windows component. Attackers may insert malicious payload following the legitimate value to launch a malicious payload.

Platforms: Windows
Domain: Host
Subtypes: Process, Registry
Submitted: 2021-11-28
Contributors: Lucas Heiligenstein

ATT&CK coverage

Technique	Tactics	Coverage
T1547 Boot or Logon Autostart ExecutionT1547.004	Persistence, Privilege Escalation	Medium
T1112 Modify Registry	Stealth (formerly Defense Evasion)	Medium

2 techniques, 3 ATT&CK ids including sub-techniques. Links open MITRE ATT&CK.

Marked techniques are also explained, with detection notes and certification relevance, on our interactive ATT&CK map.

D3FEND techniques MITRE maps to this analytic

D3-PSA Process Spawn Analysis

Data model references

Fields from the CAR data model (object/action/field) the analytic reads.

Pseudocode and implementations

PseudocodeUserinit/Shell/Notify Registry ModificationsData model: CAR native

This detects logon registry key modification, either via a new process (command line) or direct registry manipulation.

processes = search Process:create
logon_reg_processes = filter processes where command_line CONTAINS("*\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon*") AND (command_line CONTAINS("*Userinit*") OR command_line CONTAINS("*Shell*") OR command_line CONTAINS("*Notify*")) AND (((command_line CONTAINS("*reg*") OR command_line CONTAINS("*add*") OR command_line CONTAINS("*/d*")) OR (command_line CONTAINS("*Set-ItemProperty*") OR command_line CONTAINS("*New-ItemProperty*") OR command_line CONTAINS("*-value*"))))
reg_keys = search Registry:value_edit
logon_reg_keys = filter reg_keys where (value="Userinit" OR value="Shell" OR value="Notify")
output logon_reg_processes, logon_reg_keys

SplunkSplunk Search - Modification of Userinit, Shell or Notify

This is a Splunk representation of the above pseudocode.

(((((EventCode="4688" OR EventCode="1") ((CommandLine="*reg*" CommandLine="*add*" CommandLine="*/d*") OR ((CommandLine="*Set-ItemProperty*" OR CommandLine="*New-ItemProperty*") CommandLine="*-value*")) CommandLine="*\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon*" (CommandLine="*Userinit*" OR CommandLine="*Shell*" OR CommandLine="*Notify*")) OR ((EventCode="4657") (ObjectValueName="Userinit" OR ObjectValueName="Shell" OR ObjectValueName="Notify"))) OR ((EventCode="13") (TargetObject="*Userinit" OR TargetObject="*Shell" OR TargetObject="*Notify"))))

ElasticElastic Search - Modification of Userinit, Shell or Notify

This is an ElasticSearch representation of the above pseudocode.

(((EventCode:("4688" OR "1") AND ((process.command_line:*reg* AND process.command_line:*add* AND process.command_line:*\/d*) OR (process.command_line:(*Set\-ItemProperty* OR *New\-ItemProperty*) AND process.command_line:*\-value*)) AND process.command_line:*\\Microsoft\\Windows\ NT\\CurrentVersion\\Winlogon* AND process.command_line:(*Userinit* OR *Shell* OR *Notify*)) OR (EventCode:"4657" AND winlog.event_data.ObjectValueName:("Userinit" OR "Shell" OR "Notify"))) OR (EventCode:"13" AND winlog.event_data.TargetObject:(*Userinit OR *Shell OR *Notify)))

LogPointLogPoint Search - Modification of Userinit, Shell or Notify

This is a LogPoint representation of the above pseudocode.

(((EventCode IN ["4688", "1"] ((CommandLine="*reg*" CommandLine="*add*" CommandLine="*/d*") OR (CommandLine IN ["*Set-ItemProperty*", "*New-ItemProperty*"] CommandLine="*-value*")) CommandLine="*\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon*" CommandLine IN ["*Userinit*", "*Shell*", "*Notify*"]) OR (EventCode IN "4657" ObjectValueName IN ["Userinit", "Shell", "Notify"])) OR (EventCode IN "13" TargetObject IN ["*Userinit", "*Shell", "*Notify"]))

Across MITRE's defensive frameworks

Linked through the 2 ATT&CK techniques above.

Counter with D3FEND

Defensive techniques MITRE D3FEND maps to the same ATT&CK techniques.

13 more in the full list

View CAR-2021-11-002 on car.mitre.org