Windows: fsutil SymlinkEvaluation behavior modification via command line

Alerts on fsutil commands from cmd/PowerShell that change NTFS SymlinkEvaluation behavior, potentially enabling remote symlink access.

FreeReviewedSigma · Medium · v2

Product: windows
Category: process_creation
Author: frack113, The DFIR Report (SigmaHQ), DRL 1.1
Published: 2022-03-02
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059Command and Scripting Interpreter
Persistence
Priv Esc
Defense Evasion
- T1222.001Windows Permissions
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags process executions where fsutil sets the Windows SymlinkEvaluation behavior, indicating a change to how NTFS symlinks are evaluated. Attackers may use this to allow different symlink target evaluations (such as remote-to-local or remote-to-remote), which can support various access and deception techniques. It relies on Windows process creation telemetry capturing the executable (cmd.exe or PowerShell) and the full command line containing fsutil, behavior set, and SymlinkEvaluation with specific R2L/R2R/L2L parameters.

Reporting behind it

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Windows: fsutil SymlinkEvaluation behavior modification via command line

Pivot detection · T1059 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-fsutil-symlinkevaluation-behavior-change-via-cmd-or-powershell-c0b2768a

title: "Windows: fsutil SymlinkEvaluation behavior modification via command line"
id: 5351bb2b-5ac6-4113-9b0a-73e0ac521edb
status: test
description: This rule flags process executions where fsutil sets the Windows SymlinkEvaluation behavior, indicating a change to how NTFS symlinks are evaluated. Attackers may use this to allow different symlink target evaluations (such as remote-to-local or remote-to-remote), which can support various access and deception techniques. It relies on Windows process creation telemetry capturing the executable (cmd.exe or PowerShell) and the full command line containing fsutil, behavior set, and SymlinkEvaluation with specific R2L/R2R/L2L parameters.
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/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_fsutil_symlinkevaluation.yml
author: frack113, The DFIR Report, Huntrule Team
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:
    - 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
      - R2R:1
      - L2L:1
  condition: all of selection_*
falsepositives:
  - Legitimate usage, investigate the parent process and context to determine if benign.
level: medium
license: DRL-1.1
related:
  - id: c0b2768a-dd06-4671-8339-b16ca8d1f27f
    type: derived

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