Potential Ransomware Activity Using LegalNotice Message — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: high. Source dates: 2022-12-11 / 2023-08-17.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: f75ea7cd412310a6421999a34b5278dfb3e1974adb6f49b05380fe7fc825364a

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 Ransomware Activity Using LegalNotice Message
id: 8b9606c9-28be-4a38-b146-0e313cc232c1
status: test
description: Detect changes to the "LegalNoticeCaption" or "LegalNoticeText" registry values where the message set contains keywords often used in ransomware ransom messages
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/5c1e6f1b4fafd01c8d1ece85f510160fc1275fbf/atomics/T1491.001/T1491.001.md
author: frack113
date: 2022-12-11
modified: 2023-08-17
tags:
    - attack.impact
    - attack.t1491.001
logsource:
    product: windows
    category: registry_set
detection:
    selection:
        TargetObject|contains:
            - '\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\LegalNoticeCaption'
            - '\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\LegalNoticeText'
        Details|contains:
            - 'encrypted'
            - 'Unlock-Password'
            - 'paying'
    condition: selection
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://github.com/redcanaryco/atomic-red-team/blob/5c1e6f1b4fafd01c8d1ece85f510160fc1275fbf/atomics/T1491.001/T1491.001.md