Remote File Download Via Findstr.EXE — Sigma Rule

Rule metadata and linked tags

Author: Furkan CALISKAN, @caliskanfurkan_, @oscd_initiative, Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2020-10-05 / 2024-03-05.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 3138e308f8b59e0de480e5bbece23c094559b8f31eba77cecf46a4a330061cf5

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: Remote File Download Via Findstr.EXE
id: 587254ee-a24b-4335-b3cd-065c0f1f4baa
related:
    - id: bf6c39fc-e203-45b9-9538-05397c1b4f3f
      type: obsolete
status: test
description: |
    Detects execution of "findstr" with specific flags and a remote share path. This specific set of CLI flags would allow "findstr" to download the content of the file located on the remote share as described in the LOLBAS entry.
references:
    - https://lolbas-project.github.io/lolbas/Binaries/Findstr/
    - https://oddvar.moe/2018/04/11/putting-data-in-alternate-data-streams-and-how-to-execute-it-part-2/
    - https://gist.github.com/api0cradle/cdd2d0d0ec9abb686f0e89306e277b8f
author: Furkan CALISKAN, @caliskanfurkan_, @oscd_initiative, Nasreddine Bencherchali (Nextron Systems)
date: 2020-10-05
modified: 2024-03-05
tags:
    - attack.credential-access
    - attack.command-and-control
    - attack.stealth
    - attack.t1218
    - attack.t1564.004
    - attack.t1552.001
    - attack.t1105
logsource:
    category: process_creation
    product: windows
detection:
    selection_findstr:
        - CommandLine|contains: findstr
        - Image|endswith: 'findstr.exe'
        - OriginalFileName: 'FINDSTR.EXE'
    selection_cli_download_1:
        CommandLine|contains|windash: ' -v '
    selection_cli_download_2:
        CommandLine|contains|windash: ' -l '
    selection_cli_download_3:
        CommandLine|contains: '\\\\'
    condition: selection_findstr and all of selection_cli_download_*
falsepositives:
    - Unknown
level: medium

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://lolbas-project.github.io/lolbas/Binaries/Findstr/
• https://oddvar.moe/2018/04/11/putting-data-in-alternate-data-streams-and-how-to-execute-it-part-2/
• https://gist.github.com/api0cradle/cdd2d0d0ec9abb686f0e89306e277b8f