Potential Privilege Escalation Using Symlink Between Osk and Cmd — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: high. Source dates: 2022-12-11 / 2022-12-20.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 52e64f4194078e3d7682b6ea39be5c2ff167eee33b7778e16a15b03bc0e232a7

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: Potential Privilege Escalation Using Symlink Between Osk and Cmd
id: e9b61244-893f-427c-b287-3e708f321c6b
status: test
description: Detects the creation of a symbolic link between "cmd.exe" and the accessibility on-screen keyboard binary (osk.exe) using "mklink". This technique provides an elevated command prompt to the user from the login screen without the need to log in.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/5c1e6f1b4fafd01c8d1ece85f510160fc1275fbf/atomics/T1546.008/T1546.008.md
    - https://ss64.com/nt/mklink.html
author: frack113
date: 2022-12-11
modified: 2022-12-20
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1546.008
logsource:
    product: windows
    category: process_creation
detection:
    selection_img:
        - Image|endswith: '\cmd.exe'
        - OriginalFileName: 'Cmd.Exe'
    selection_cli:
        CommandLine|contains|all:
            - 'mklink'
            - '\osk.exe'
            - '\cmd.exe'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_cmd_mklink_osk_cmd/info.yml

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://github.com/redcanaryco/atomic-red-team/blob/5c1e6f1b4fafd01c8d1ece85f510160fc1275fbf/atomics/T1546.008/T1546.008.md
• https://ss64.com/nt/mklink.html