Scheduled Task Execution at Scale via GPO

[metadata]
creation_date = "2021/11/08"
integration = ["system", "windows"]
maturity = "production"
updated_date = "2025/03/20"

[rule]
author = ["Elastic"]
description = """
Detects the modification of Group Policy Object attributes to execute a scheduled task in the objects controlled by the
GPO.
"""
index = ["logs-system.security*", "logs-windows.forwarded*", "winlogbeat-*"]
language = "eql"
license = "Elastic License v2"
name = "Scheduled Task Execution at Scale via GPO"
note = """## Triage and analysis

### Investigating Scheduled Task Execution at Scale via GPO

Group Policy Objects (GPOs) 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 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 allowed and done under change management, and if the execution is legitimate.

### Related rules

- Group Policy Abuse for Privilege Addition - b9554892-5e0e-424b-83a0-5aef95aa43bf
- Startup/Logon Script added to Group Policy Object - 16fac1a1-21ee-4ca6-b720-458e3855d046

### 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 scheduled tasks 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).
"""
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",
    "https://twitter.com/menasec1/status/1106899890377052160",
    "https://github.com/SigmaHQ/sigma/blob/master/rules/windows/builtin/security/win_gpo_scheduledtasks.yml",
]
risk_score = 47
rule_id = "15a8ba77-1c13-4274-88fe-6bd14133861e"
setup = """## Setup

The 'Audit Detailed File Share' audit policy must be configured (Success Failure).
Steps to implement the logging policy 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 must be configured (Success Failure).
Steps to implement the logging policy 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)
```
"""
severity = "medium"
tags = [
    "Domain: Endpoint",
    "OS: Windows",
    "Use Case: Threat Detection",
    "Tactic: Privilege Escalation",
    "Tactic: Lateral Movement",
    "Data Source: Active Directory",
    "Resources: Investigation Guide",
    "Use Case: Active Directory Monitoring",
    "Data Source: Windows Security Event Logs",
]
timestamp_override = "event.ingested"
type = "eql"

query = '''
any where host.os.type == "windows" and event.code in ("5136", "5145") and
(
  (
    winlog.event_data.AttributeLDAPDisplayName : (
      "gPCMachineExtensionNames",
      "gPCUserExtensionNames"
    ) and
    winlog.event_data.AttributeValue : "*CAB54552-DEEA-4691-817E-ED4A4D1AFC72*" and
    winlog.event_data.AttributeValue : "*AADCED64-746C-4633-A97C-D61349046527*"
  ) or
  (
    winlog.event_data.ShareName : "\\\\*\\SYSVOL" and
    winlog.event_data.RelativeTargetName : "*ScheduledTasks.xml" and
    winlog.event_data.AccessList:"*%%4417*"
  )
)
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1053"
name = "Scheduled Task/Job"
reference = "https://attack.mitre.org/techniques/T1053/"
[[rule.threat.technique.subtechnique]]
id = "T1053.005"
name = "Scheduled Task"
reference = "https://attack.mitre.org/techniques/T1053/005/"


[[rule.threat.technique]]
id = "T1484"
name = "Domain or Tenant Policy Modification"
reference = "https://attack.mitre.org/techniques/T1484/"
[[rule.threat.technique.subtechnique]]
id = "T1484.001"
name = "Group Policy Modification"
reference = "https://attack.mitre.org/techniques/T1484/001/"



[rule.threat.tactic]
id = "TA0004"
name = "Privilege Escalation"
reference = "https://attack.mitre.org/tactics/TA0004/"
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1570"
name = "Lateral Tool Transfer"
reference = "https://attack.mitre.org/techniques/T1570/"


[rule.threat.tactic]
id = "TA0008"
name = "Lateral Movement"
reference = "https://attack.mitre.org/tactics/TA0008/"