Scheduled Task Execution at Scale via GPO

Detects the modification of Group Policy Object attributes to execute a scheduled task in the objects controlled by the GPO.

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:

Tags:

Elastic
Host
Windows
Threat Detection
Privilege Escalation
Active Directory

Version: 2

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 can be used by attackers to execute scheduled tasks at scale to compromise objects controlled by a
given GPO. This is done by changing the contents of the `<GPOPath>\Machine\Preferences\ScheduledTasks\ScheduledTasks.xml`
file.

#### Possible investigation steps:
- This attack abuses a legitimate mechanism of the 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, ánd check the `<Command>` and `<Arguments>` XML tags for any
potentially malicious commands and binaries.
- If the action is suspicious for the user, check for any other activities done by the user in the last 48 hours.

### False Positive Analysis
- Verify if the execution is allowed and done under change management, and if the execution is legitimate.

### Related Rules
- Group Policy Abuse for Privilege Addition
- Startup/Logon Script added to Group Policy Object

### Response and Remediation
- Immediate response should be taken to validate activity, investigate, and potentially isolate activity to prevent further
post-compromise behavior.

## Config

The 'Audit Detailed File Share' audit policy is required be configured (Success Failure).
Steps to implement the logging policy with with Advanced Audit Configuration:
```
Computer Configuration >
Policies >
Windows Settings >
Security Settings >
Advanced Audit Policies Configuration >
Audit Policies >
Object Access >
Audit Detailed File Share (Success,Failure)
```

The 'Audit Directory Service Changes' audit policy is required be configured (Success Failure).
Steps to implement the logging policy with with Advanced Audit Configuration:
```
Computer Configuration >
Policies >
Windows Settings >
Security Settings >
Advanced Audit Policies Configuration >
Audit Policies >
DS Access >
Audit Directory Service Changes (Success,Failure)
```

Rule query

edit

(event.code: "5136" and winlog.event_data.AttributeLDAPDisplayName:("gPCMachineExtensionNames" or "gPCUserExtensionNames") and
   winlog.event_data.AttributeValue:(*CAB54552-DEEA-4691-817E-ED4A4D1AFC72* and *AADCED64-746C-4633-A97C-D61349046527*))
or
(event.code: "5145" and winlog.event_data.ShareName: "\\\\*\\SYSVOL" and winlog.event_data.RelativeTargetName: *ScheduledTasks.xml and
  (message: WriteData or winlog.event_data.AccessList: *%%4417*))

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Privilege Escalation
- ID: TA0004
- Reference URL: https://attack.mitre.org/tactics/TA0004/
Technique:
- Name: Scheduled Task/Job
- ID: T1053
- Reference URL: https://attack.mitre.org/techniques/T1053/
Sub-technique:
- Name: Scheduled Task
- ID: T1053.005
- Reference URL: https://attack.mitre.org/techniques/T1053/005/
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/

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