Sigma rule: Potentially Suspicious NTFS Symlink Behavior Modification

Rule

Title

Potentially Suspicious NTFS Symlink Behavior Modification

Status

test

Level

medium

Author

frack113, The DFIR Report

Date

2022-03-02

Modified

2025-11-13

File

rules/windows/process_creation/proc_creation_win_fsutil_symlinkevaluation.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

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.

Log source

product

windows

category

process_creation

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_*

False positives (as the rule lists them)

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

Tags

• attack.execution
• attack.defense-impairment
• attack.t1059
• attack.t1222.001

MITRE ATT&CK ids this rule names

• T1059
• T1222.001

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/

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_fsutil_symlinkevaluation.yml