Suspicious Command Patterns In Scheduled Task Creation — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems). Source status: test; severity: high. Source dates: 2022-02-23 / 2024-03-19.

{
  "product": "windows",
  "category": "process_creation"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 8f2dea3f06ca14d8556f7efb32d0c20d1aea9b1a51e31ff36142db24ed4baa01

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Suspicious Command Patterns In Scheduled Task Creation
id: f2c64357-b1d2-41b7-849f-34d2682c0fad
status: test
description: Detects scheduled task creation using "schtasks" that contain potentially suspicious or uncommon commands
references:
    - https://app.any.run/tasks/512c1352-6380-4436-b27d-bb62f0c020d6/
    - https://twitter.com/RedDrip7/status/1506480588827467785
    - https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/devil-bait/NCSC-MAR-Devil-Bait.pdf
author: Florian Roth (Nextron Systems)
date: 2022-02-23
modified: 2024-03-19
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.execution
    - attack.t1053.005
logsource:
    product: windows
    category: process_creation
detection:
    selection_schtasks:
        Image|endswith: '\schtasks.exe'
        CommandLine|contains: '/Create '
    selection_pattern_1:
        CommandLine|contains:
            - '/sc minute '
            - '/ru system '
    selection_pattern_2:
        CommandLine|contains:
            - 'cmd /c'
            - 'cmd /k'
            - 'cmd /r'
            - 'cmd.exe /c '
            - 'cmd.exe /k '
            - 'cmd.exe /r '
    selection_uncommon:
        CommandLine|contains:
            - ' -decode '
            - ' -enc '
            - ' -w hidden '
            - ' bypass '
            - ' IEX'
            - '.DownloadData'
            - '.DownloadFile'
            - '.DownloadString'
            - '/c start /min ' # https://twitter.com/RedDrip7/status/1506480588827467785
            - 'FromBase64String'
            - 'mshta http'
            - 'mshta.exe http'
    selection_anomaly_1:
        CommandLine|contains:
            - ':\ProgramData\'
            - ':\Temp\'
            - ':\Tmp\'
            - ':\Users\Public\'
            - ':\Windows\Temp\'
            - '\AppData\'
            - '%AppData%'
            - '%Temp%'
            - '%tmp%'
    selection_anomaly_2:
        CommandLine|contains:
            - 'cscript'
            - 'curl'
            - 'wscript'
    condition: selection_schtasks and ( all of selection_pattern_* or selection_uncommon or all of selection_anomaly_* )
falsepositives:
    - Software installers that run from temporary folders and also install scheduled tasks are expected to generate some false positives
level: high

Original YAML and metadata in JSON

False positives

• Software installers that run from temporary folders and also install scheduled tasks are expected to generate some false positives

Source references

• https://app.any.run/tasks/512c1352-6380-4436-b27d-bb62f0c020d6/
• https://twitter.com/RedDrip7/status/1506480588827467785
• https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/devil-bait/NCSC-MAR-Devil-Bait.pdf