Suspicious Scheduled Task Update

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

Detects update to a scheduled task event that contain suspicious keywords.

title: Suspicious Scheduled Task Update
id: 614cf376-6651-47c4-9dcc-6b9527f749f4
related:
    - id: 1c0e41cd-21bb-4433-9acc-4a2cd6367b9b # ProcCreation schtasks change
      type: similar
status: test
description: Detects update to a scheduled task event that contain suspicious keywords.
references:
    - https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-10/security/threat-protection/auditing/event-4698
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-12-05
tags:
    - attack.execution
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1053.005
logsource:
    product: windows
    service: security
    definition: 'The Advanced Audit Policy setting Object Access > Audit Other Object Access Events has to be configured to allow this detection. We also recommend extracting the Command field from the embedded XML in the event data.'
detection:
    selection_eid:
        EventID: 4702
    selection_paths:
        TaskContentNew|contains:
            - '\AppData\Local\Temp\'
            - '\AppData\Roaming\'
            - '\Users\Public\'
            - '\WINDOWS\Temp\'
            - 'C:\Temp\'
            - '\Desktop\'
            - '\Downloads\'
            - '\Temporary Internet'
            - 'C:\ProgramData\'
            - 'C:\Perflogs\'
    selection_commands:
        TaskContentNew|contains:
            - 'regsvr32'
            - 'rundll32'
            - 'cmd.exe</Command>'
            - 'cmd</Command>'
            - '<Arguments>/c '
            - '<Arguments>/k '
            - '<Arguments>/r '
            - 'powershell'
            - 'pwsh'
            - 'mshta'
            - 'wscript'
            - 'cscript'
            - 'certutil'
            - 'bitsadmin'
            - 'bash.exe'
            - 'bash '
            - 'scrcons'
            - 'wmic '
            - 'wmic.exe'
            - 'forfiles'
            - 'scriptrunner'
            - 'hh.exe'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high

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

4578c2d4-8461-407e-ac0e-e5aaa6c8119a

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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.

Rejected pattern present

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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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