Suspicious Word Cab File Write CVE-2021-40444

title: Suspicious Word Cab File Write CVE-2021-40444
id: 60c0a111-787a-4e8a-9262-ee485f3ef9d5
status: test
description: Detects file creation patterns noticeable during the exploitation of CVE-2021-40444
references:
    - https://twitter.com/RonnyTNL/status/1436334640617373699?s=20
    - https://twitter.com/vanitasnk/status/1437329511142420483?s=21
author: Florian Roth (Nextron Systems), Sittikorn S
date: 2021-09-10
modified: 2023-06-22
tags:
    - attack.resource-development
    - attack.t1587
    - detection.emerging-threats
logsource:
    product: windows
    category: file_event
detection:
    selection_cab:
        Image|endswith: '\winword.exe'
        TargetFilename|contains: '\Windows\INetCache'
        TargetFilename|endswith: '.cab'
    selection_inf:
        Image|endswith: '\winword.exe'
        TargetFilename|contains|all:
            - '\AppData\Local\Temp\'
            - '.inf'
    filter_main_legit:
        TargetFilename|startswith: 'C:\Users\'
        TargetFilename|contains: 'AppData\Local\Temp'
        TargetFilename|endswith: '\Content.inf'
    condition: 1 of selection_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high