Scheduled Task Execution at Scale via GPO
editScheduled Task Execution at Scale via GPO
editDetects 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:
- 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
Tags:
- Elastic
- Host
- Windows
- Threat Detection
- Privilege Escalation
- Active Directory
Version: 6
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 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).
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&CKTM
-
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/