Windows Root Certificate Installation from Suspicious Paths via PowerShell Import-Certificate

title: Windows Root Certificate Installation from Suspicious Paths via PowerShell Import-Certificate
id: d4d478be-4dce-481b-a2b0-aee3d530cdbd
status: test
description: This rule flags Windows process executions where PowerShell imports a certificate into the local machine trusted root store (Cert:\LocalMachine\Root) using Import-Certificate. It narrows to executions that reference file locations commonly abused for staging or user-writable content, such as Temp, Desktop, Downloads, Perflogs, and Public/AppData paths. Installing a root certificate can help attackers trust malicious TLS endpoints and reduce browser or application warnings. Telemetry relies on Windows process creation events including the full command line, specifically matching Import-Certificate targeting the Root store and the suspicious path strings.
references:
  - https://www.microsoft.com/security/blog/2022/09/07/profiling-dev-0270-phosphorus-ransomware-operations/
  - https://learn.microsoft.com/en-us/powershell/module/pki/import-certificate?view=windowsserver2022-ps
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_import_cert_susp_locations.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2022-09-09
modified: 2023-01-16
tags:
  - attack.defense-impairment
  - attack.t1553.004
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    CommandLine|contains|all:
      - Import-Certificate
      - " -FilePath "
      - Cert:\LocalMachine\Root
    CommandLine|contains:
      - \AppData\Local\Temp\
      - :\Windows\TEMP\
      - \Desktop\
      - \Downloads\
      - \Perflogs\
      - :\Users\Public\
  condition: selection
falsepositives:
  - Unlikely
level: high
license: DRL-1.1
related:
  - id: 5f6a601c-2ecb-498b-9c33-660362323afa
    type: derived