Startup/Logon Script Added to Group Policy Object

Status: test
Severity: medium
Log source: product windows, service security
Author: Elastic, Josh Nickels, Marius Rothenbücher
Source: github.com/SigmaHQ/sigma

Detects the modification of Group Policy Objects (GPO) to add a startup/logon script to users or computer objects.

Known false positives

Legitimate execution by system administrators.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1547` Boot or Logon Autostart Execution
Privilege Escalation	`T1484.001` Domain or Tenant Policy Modification: Group Policy Modification `T1547` Boot or Logon Autostart Execution
Defense Impairment	`T1484.001` Domain or Tenant Policy Modification: Group Policy Modification

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 5136: A directory service object was modified.
Security-Auditing	Event ID 5145: A network share object was checked to see whether client can be granted desired access.

Rule body

title: Startup/Logon Script Added to Group Policy Object
id: 123e4e6d-b123-48f8-b261-7214938acaf0
status: test
description: |
    Detects the modification of Group Policy Objects (GPO) to add a startup/logon script to users or computer objects.
references:
    - https://www.elastic.co/guide/en/security/current/startup-logon-script-added-to-group-policy-object.html
author: Elastic, Josh Nickels, Marius Rothenbücher
date: 2024-09-06
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.defense-impairment
    - attack.t1484.001
    - attack.t1547
logsource:
    product: windows
    service: security
    definition: 'The advanced audit policy setting "Object Access > Audit Detailed File Share" must be configured for Success/Failure'
detection:
    selection_eventid:
        EventID:
            - 5136
            - 5145
    selection_attributes_main:
        AttributeLDAPDisplayName:
            - 'gPCMachineExtensionNames'
            - 'gPCUserExtensionNames'
        AttributeValue|contains: '42B5FAAE-6536-11D2-AE5A-0000F87571E3'
    selection_attributes_optional:
        AttributeValue|contains:
            - '40B6664F-4972-11D1-A7CA-0000F87571E3'
            - '40B66650-4972-11D1-A7CA-0000F87571E3'
    selection_share:
        ShareName|endswith: '\SYSVOL'
        RelativeTargetName|endswith:
            - '\scripts.ini'
            - '\psscripts.ini'
        AccessList|contains: '%%4417'
    condition: selection_eventid and (all of selection_attributes_* or selection_share)
falsepositives:
    - Legitimate execution by system administrators.
level: medium

Stages and Predicates

Stage 0: `condition`

selection_eventid and (all of selection_attributes_* or selection_share)

Stage 1: `selection_eventid`

selection_eventid:
    EventID:
        - 5136
        - 5145

Stage 2: `selection_attributes_main`

selection_attributes_main:
    AttributeLDAPDisplayName:
        - 'gPCMachineExtensionNames'
        - 'gPCUserExtensionNames'
    AttributeValue|contains: '42B5FAAE-6536-11D2-AE5A-0000F87571E3'

Stage 3: `selection_attributes_optional`

selection_attributes_optional:
    AttributeValue|contains:
        - '40B6664F-4972-11D1-A7CA-0000F87571E3'
        - '40B66650-4972-11D1-A7CA-0000F87571E3'

Stage 4: `selection_share`

selection_share:
    ShareName|endswith: '\SYSVOL'
    RelativeTargetName|endswith:
        - '\scripts.ini'
        - '\psscripts.ini'
    AccessList|contains: '%%4417'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`AccessList`	match	`%%4417` corpus 11 (sigma 8, elastic 2, splunk 1)	`field:"AccessList" kind:match value:"%%4417"`
`AttributeLDAPDisplayName`	eq	`gPCMachineExtensionNames` corpus 7 (sigma 3, elastic 3, splunk 1) `gPCUserExtensionNames` corpus 4 (sigma 2, elastic 2)	`field:"AttributeLDAPDisplayName" kind:eq`
`AttributeValue`	match	`40B6664F-4972-11D1-A7CA-0000F87571E3` corpus 2 (sigma 1, elastic 1) `40B66650-4972-11D1-A7CA-0000F87571E3` corpus 2 (sigma 1, elastic 1) `42B5FAAE-6536-11D2-AE5A-0000F87571E3` corpus 2 (sigma 1, elastic 1)	`field:"AttributeValue" kind:match`
`RelativeTargetName`	ends_with	`\psscripts.ini` corpus 2 (sigma 1, elastic 1) `\scripts.ini` corpus 2 (sigma 1, elastic 1)	`field:"RelativeTargetName" kind:ends_with`
`ShareName`	ends_with	`\SYSVOL` corpus 2 (sigma 2)	`field:"ShareName" kind:ends_with value:"\SYSVOL"`

Startup/Logon Script Added to Group Policy Object

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_eventid

Stage 2: selection_attributes_main

Stage 3: selection_attributes_optional

Stage 4: selection_share

Indicators

Stage 0: `condition`

Stage 1: `selection_eventid`

Stage 2: `selection_attributes_main`

Stage 3: `selection_attributes_optional`

Stage 4: `selection_share`