Base64 Encoded PowerShell Command Detected — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems). Source status: test; severity: high. Source dates: 2020-01-29 / 2023-01-26.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 66a4fcf31220cd42a87b6d713a2e23ee0ebc7b05e3ea0ffbf5b1de766a92e16b

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: Base64 Encoded PowerShell Command Detected
id: e32d4572-9826-4738-b651-95fa63747e8a
status: test
description: Detects usage of the "FromBase64String" function in the commandline which is used to decode a base64 encoded string
references:
    - https://gist.github.com/Neo23x0/6af876ee72b51676c82a2db8d2cd3639
author: Florian Roth (Nextron Systems)
date: 2020-01-29
modified: 2023-01-26
tags:
    - attack.stealth
    - attack.t1027
    - attack.execution
    - attack.t1140
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains: '::FromBase64String('
    condition: selection
falsepositives:
    - Administrative script libraries
level: high

Original YAML and metadata in JSON

False positives

• Administrative script libraries

Source references

• https://gist.github.com/Neo23x0/6af876ee72b51676c82a2db8d2cd3639