Potentially Suspicious NTFS Symlink Behavior Modification — Sigma Rule

Rule metadata and linked tags

Author: frack113, The DFIR Report. Source status: test; severity: medium. Source dates: 2022-03-02 / 2025-11-13.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 7771ffbbdb573f2177445bbf07cabdeb3c72840804da7cb4bcbaad9fd41f4df3

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: Potentially Suspicious NTFS Symlink Behavior Modification
id: c0b2768a-dd06-4671-8339-b16ca8d1f27f
status: test
description: |
    Detects the modification of NTFS symbolic link behavior using fsutil, which could be used to enable remote to local or remote to remote symlinks for potential attacks.
references:
    - https://www.cybereason.com/blog/cybereason-vs.-blackcat-ransomware
    - https://learn.microsoft.com/fr-fr/windows-server/administration/windows-commands/fsutil-behavior
    - https://thedfirreport.com/2025/06/30/hide-your-rdp-password-spray-leads-to-ransomhub-deployment/
author: frack113, The DFIR Report
date: 2022-03-02
modified: 2025-11-13
tags:
    - attack.execution
    - attack.defense-impairment
    - attack.t1059
    - attack.t1222.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_img_proxy:
        # Note: Example command observed:  cmd.exe /c "fsutil behaviour set SymlinkEvaluation"
        - Image|endswith:
              - '\cmd.exe'
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'Cmd.Exe'
              - 'PowerShell.EXE'
              - 'pwsh.dll'
    selection_fsutil_cli:
        CommandLine|contains|all:
            - 'fsutil'
            - 'behavior'
            - 'set'
            - 'SymlinkEvaluation'
    selection_symlink_params:
        CommandLine|contains:
            - 'R2L:1' # Remote to Local
            - 'R2R:1' # Remote to Remote
            - 'L2L:1' # Local to Local
    condition: all of selection_*
falsepositives:
    - Legitimate usage, investigate the parent process and context to determine if benign.
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate usage, investigate the parent process and context to determine if benign.

Source references

• https://www.cybereason.com/blog/cybereason-vs.-blackcat-ransomware
• https://learn.microsoft.com/fr-fr/windows-server/administration/windows-commands/fsutil-behavior
• https://thedfirreport.com/2025/06/30/hide-your-rdp-password-spray-leads-to-ransomhub-deployment/