Windows Process Creation: Suspicious calc.exe Command-Line Usage Outside System Locations

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1036Masquerading
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

Flags Windows process creation events where calc.exe is launched with command-line parameters or where the calc.exe image path does not match common system directories. Attackers often use built-in Windows binaries like calc.exe for living-off-the-land testing, probing, or to blend in with legitimate activity. This rule relies on process creation telemetry, specifically the Image path and CommandLine contents to identify suspicious execution context.

Reporting behind it

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Windows Process Creation: Suspicious calc.exe Command-Line Usage Outside System Locations

Pivot detection · T1036 · 9 related

Changelog

v2

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-process-creation-suspicious-calc-exe-command-line-or-non-system-path-737e618a

title: "Windows Process Creation: Suspicious calc.exe Command-Line Usage Outside System Locations"
id: 7cfe42ab-dbaa-4ab5-a52b-528d3ac20947
status: test
description: Flags Windows process creation events where calc.exe is launched with command-line parameters or where the calc.exe image path does not match common system directories. Attackers often use built-in Windows binaries like calc.exe for living-off-the-land testing, probing, or to blend in with legitimate activity. This rule relies on process creation telemetry, specifically the Image path and CommandLine contents to identify suspicious execution context.
references:
  - https://twitter.com/ItsReallyNick/status/1094080242686312448
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_calc_uncommon_exec.yml
author: Florian Roth (Nextron Systems), Huntrule Team
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
license: DRL-1.1
related:
  - id: 737e618a-a410-49b5-bec3-9e55ff7fbc15
    type: derived

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