Startup/Logon Script added to Group Policy Object
editStartup/Logon Script added to Group Policy Object
editDetects the modification of Group Policy Objects (GPO) to add a startup/logon script to users or computer objects.
Rule type: query
Rule indices:
- winlogbeat-*
- logs-system.*
Severity: medium
Risk score: 47
Runs every: 5m
Searches indices from: None (Date Math format, see also Additional look-back time)
Maximum alerts per execution: 100
References:
- https://github.com/atc-project/atc-data/blob/master/docs/Logging_Policies/LP_0025_windows_audit_directory_service_changes.md
- https://github.com/atc-project/atc-data/blob/f2bbb51ecf68e2c9f488e3c70dcdd3df51d2a46b/docs/Logging_Policies/LP_0029_windows_audit_detailed_file_share.md
- https://labs.f-secure.com/tools/sharpgpoabuse
Tags:
- Elastic
- Host
- Windows
- Threat Detection
- Privilege Escalation
- Active Directory
- Investigation Guide
Version: 102
Rule authors:
- Elastic
Rule license: Elastic License v2
Investigation guide
edit## Triage and analysis ### Investigating Scheduled Task Execution at Scale via GPO Group Policy Objects (GPOs) can be used by attackers to instruct arbitrarily large groups of clients to execute specified commands at startup, logon, shutdown, and logoff. This is done by creating or modifying the `scripts.ini` or `psscripts.ini` files. The scripts are stored in the following path: `<GPOPath>\Machine\Scripts\`, `<GPOPath>\User\Scripts\` #### Possible investigation steps - This attack abuses a legitimate mechanism of Active Directory, so it is important to determine whether the activity is legitimate and the administrator is authorized to perform this operation. - Retrieve the contents of the `ScheduledTasks.xml` file, and check the `<Command>` and `<Arguments>` XML tags for any potentially malicious commands or binaries. - Investigate other alerts associated with the user/host during the past 48 hours. - Scope which objects may be compromised by retrieving information about which objects are controlled by the GPO. ### False positive analysis - Verify if the execution is legitimately authorized and executed under a change management process. ### Related rules - Group Policy Abuse for Privilege Addition - b9554892-5e0e-424b-83a0-5aef95aa43bf - Scheduled Task Execution at Scale via GPO - 15a8ba77-1c13-4274-88fe-6bd14133861e ### Response and remediation - Initiate the incident response process based on the outcome of the triage. - The investigation and containment must be performed in every computer controlled by the GPO, where necessary. - Remove the script from the GPO. - Check if other GPOs have suspicious scripts attached. - Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector. - Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
Rule query
edit(
event.code:5136 and winlog.event_data.AttributeLDAPDisplayName:(gPCMachineExtensionNames or gPCUserExtensionNames) and
winlog.event_data.AttributeValue:(*42B5FAAE-6536-11D2-AE5A-0000F87571E3* and
(*40B66650-4972-11D1-A7CA-0000F87571E3* or *40B6664F-4972-11D1-A7CA-0000F87571E3*))
)
or
(
event.code:5145 and winlog.event_data.ShareName:\\\\*\\SYSVOL and
winlog.event_data.RelativeTargetName:(*\\scripts.ini or *\\psscripts.ini) and
(message:WriteData or winlog.event_data.AccessList:*%%4417*)
)
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Privilege Escalation
- ID: TA0004
- Reference URL: https://attack.mitre.org/tactics/TA0004/
-
Technique:
- Name: Boot or Logon Autostart Execution
- ID: T1547
- Reference URL: https://attack.mitre.org/techniques/T1547/
-
Technique:
- Name: Domain Policy Modification
- ID: T1484
- Reference URL: https://attack.mitre.org/techniques/T1484/
-
Sub-technique:
- Name: Group Policy Modification
- ID: T1484.001
- Reference URL: https://attack.mitre.org/techniques/T1484/001/