Suspicious Desktopimgdownldr Target File

SIGMA detection rule by Florian Roth (Nextron Systems) · NOASSERTION

Detects a suspicious Microsoft desktopimgdownldr file creation that stores a file to a suspicious location or contains a file with a suspicious extension

title: Suspicious Desktopimgdownldr Target File
id: fc4f4817-0c53-4683-a4ee-b17a64bc1039
status: test
description: Detects a suspicious Microsoft desktopimgdownldr file creation that stores a file to a suspicious location or contains a file with a suspicious extension
references:
    - https://labs.sentinelone.com/living-off-windows-land-a-new-native-file-downldr/
    - https://twitter.com/SBousseaden/status/1278977301745741825
author: Florian Roth (Nextron Systems)
date: 2020-07-03
modified: 2022-06-02
tags:
    - attack.command-and-control
    - attack.t1105
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith: '\svchost.exe'
        TargetFilename|contains: '\Personalization\LockScreenImage\'
    filter1:
        TargetFilename|contains: 'C:\Windows\'
    filter2:
        TargetFilename|contains:
            - '.jpg'
            - '.jpeg'
            - '.png'
    condition: selection and not filter1 and not filter2
falsepositives:
    - False positives depend on scripts and administrative tools used in the monitored environment
level: high

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

61d8fe21-14a4-4a05-aac9-973141b1eb56

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

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