Suspicious Schtasks Schedule Type With High Privileges

SIGMA detection rule by Nasreddine Bencherchali (Nextron Systems) · NOASSERTION

Detects scheduled task creations or modification to be run with high privileges on a suspicious schedule type

title: Suspicious Schtasks Schedule Type With High Privileges
id: 7a02e22e-b885-4404-b38b-1ddc7e65258a
related:
    - id: 24c8392b-aa3c-46b7-a545-43f71657fe98
      type: similar
status: test
description: Detects scheduled task creations or modification to be run with high privileges on a suspicious schedule type
references:
    - https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/schtasks-change
    - https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/schtasks-create
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-31
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.execution
    - attack.t1053.005
logsource:
    product: windows
    category: process_creation
detection:
    selection_img:
        - Image|endswith: '\schtasks.exe'
        - OriginalFileName: 'schtasks.exe'
    selection_time:
        CommandLine|contains:
            - ' ONLOGON '
            - ' ONSTART '
            - ' ONCE '
            - ' ONIDLE '
    selection_privs:
        CommandLine|contains:
            - 'NT AUT' # This covers the usual NT AUTHORITY\SYSTEM
            - ' SYSTEM' # SYSTEM is a valid value for schtasks hence it gets it's own value with space
            - 'HIGHEST'
    condition: all of selection_*
falsepositives:
    - Some installers were seen using this method of creation unfortunately. Filter them in your environment
level: medium

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

b2d96a8c-eb2c-48f8-bbcf-83f493a6f6eb

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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