Insensitive Subfolder Search Via Findstr.EXE

calendar Nov 15, 2023 · attack.defense_evasion attack.t1218 attack.t1564.004 attack.t1552.001 attack.t1105  ·
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Detects execution of findstr with the "s" and "i" flags for a "subfolder" and "insensitive" search respectively. Attackers sometimes leverage this built-in utility to search the system for interesting files or filter through results of commands.

Sigma rule (View on GitHub)

 1title: Insensitive Subfolder Search Via Findstr.EXE
 2id: 04936b66-3915-43ad-a8e5-809eadfd1141
 3related:
 4    - id: bf6c39fc-e203-45b9-9538-05397c1b4f3f
 5      type: obsoletes
 6status: experimental
 7description: |
 8        Detects execution of findstr with the "s" and "i" flags for a "subfolder" and "insensitive" search respectively. Attackers sometimes leverage this built-in utility to search the system for interesting files or filter through results of commands.
 9references:
10    - https://lolbas-project.github.io/lolbas/Binaries/Findstr/
11    - https://oddvar.moe/2018/04/11/putting-data-in-alternate-data-streams-and-how-to-execute-it-part-2/
12    - https://gist.github.com/api0cradle/cdd2d0d0ec9abb686f0e89306e277b8f
13author: Furkan CALISKAN, @caliskanfurkan_, @oscd_initiative, Nasreddine Bencherchali (Nextron Systems)
14date: 2020/10/05
15modified: 2023/11/12
16tags:
17    - attack.defense_evasion
18    - attack.t1218
19    - attack.t1564.004
20    - attack.t1552.001
21    - attack.t1105
22logsource:
23    category: process_creation
24    product: windows
25detection:
26    selection_findstr:
27        - CommandLine|contains: findstr
28        - Image|endswith: 'findstr.exe'
29        - OriginalFileName: 'FINDSTR.EXE'
30    selection_cli_search_subfolder:
31        CommandLine|contains:
32            - ' /s '
33            - ' -s '
34    selection_cli_search_insensitive:
35        CommandLine|contains:
36            - ' /i '
37            - ' -i '
38    condition: selection_findstr and all of selection_cli_search_*
39falsepositives:
40    - Administrative or software activity
41level: low

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