Suspicious Unblock-File — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: medium. Source dates: 2022-02-01 / not supplied.

{
  "product": "windows",
  "category": "ps_script",
  "definition": "Requirements: Script Block Logging must be enabled"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 8d734fe1c41011fa28b4c8be6bd62f383c88312a64ca228702b6b63928e5d197

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: Suspicious Unblock-File
id: 5947497f-1aa4-41dd-9693-c9848d58727d
status: test
description: Remove the Zone.Identifier alternate data stream which identifies the file as downloaded from the internet.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1553.005/T1553.005.md#atomic-test-3---remove-the-zoneidentifier-alternate-data-stream
    - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/unblock-file?view=powershell-7.2
author: frack113
date: 2022-02-01
tags:
    - attack.defense-impairment
    - attack.t1553.005
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains|all:
            - 'Unblock-File '
            - '-Path '
    condition: selection
falsepositives:
    - Legitimate PowerShell scripts
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate PowerShell scripts

Source references

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1553.005/T1553.005.md#atomic-test-3---remove-the-zoneidentifier-alternate-data-stream
• https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/unblock-file?view=powershell-7.2