Suspicious Binaries and Scripts in Public Folder — Sigma Rule

Rule metadata and linked tags

Author: The DFIR Report. Source status: experimental; severity: high. Source dates: 2025-01-23 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: a583bf93dcc6c4df34fbb396eac7a63d3f234bde8af05d74b37d22703929e6b0

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 Binaries and Scripts in Public Folder
id: b447f7de-1e53-4cbf-bfb4-f1f6d0b04e4e
status: experimental
description: Detects the creation of a file with a suspicious extension in the public folder, which could indicate potential malicious activity.
references:
    - https://intel.thedfirreport.com/events/view/30032 # Private Report
    - https://intel.thedfirreport.com/eventReports/view/70 # Private Report
    - https://thedfirreport.com/2025/01/27/cobalt-strike-and-a-pair-of-socks-lead-to-lockbit-ransomware/
author: 'The DFIR Report'
date: 2025-01-23
tags:
    - attack.execution
    - attack.t1204
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|contains: ':\Users\Public\'
        TargetFilename|endswith:
            - '.bat'
            - '.dll'
            - '.exe'
            - '.hta'
            - '.js'
            - '.ps1'
            - '.vbe'
            - '.vbs'
    condition: selection
falsepositives:
    - Administrators deploying legitimate binaries to public folders.
level: high
regression_tests_path: regression_data/rules/windows/file/file_event/file_event_win_susp_public_folder_extension/info.yml

Original YAML and metadata in JSON

False positives

• Administrators deploying legitimate binaries to public folders.

Source references

• https://intel.thedfirreport.com/events/view/30032
• https://intel.thedfirreport.com/eventReports/view/70
• https://thedfirreport.com/2025/01/27/cobalt-strike-and-a-pair-of-socks-lead-to-lockbit-ransomware/