Suspicious Calculator Usage — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems). Source status: test; severity: high. Source dates: 2019-02-09 / 2023-11-09.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 6a1e4072ed3e4c14c299ebd50ed210ab83b994b9d285d8b76ab786827c05c10f

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 Calculator Usage
id: 737e618a-a410-49b5-bec3-9e55ff7fbc15
status: test
description: |
    Detects suspicious use of 'calc.exe' with command line parameters or in a suspicious directory, which is likely caused by some PoC or detection evasion.
references:
    - https://twitter.com/ItsReallyNick/status/1094080242686312448
author: Florian Roth (Nextron Systems)
date: 2019-02-09
modified: 2023-11-09
tags:
    - attack.stealth
    - attack.t1036
logsource:
    category: process_creation
    product: windows
detection:
    selection_1:
        CommandLine|contains: '\calc.exe '
    selection_2:
        Image|endswith: '\calc.exe'
    filter_main_known_locations:
        Image|contains:
            - ':\Windows\System32\'
            - ':\Windows\SysWOW64\'
            - ':\Windows\WinSxS\'
    condition: selection_1 or ( selection_2 and not filter_main_known_locations )
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://twitter.com/ItsReallyNick/status/1094080242686312448