Windows Network Connection from Cmstp.EXE (Outbound)

Alerts on outbound network connections initiated by cmstp.exe, which is uncommon and may indicate process misuse.

FreeReviewedSigma · High · v2

Product: windows
Category: network_connection
Author: Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2022-08-30
Updated: 2026-07-31

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1218.003CMSTP
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags events where cmstp.exe initiates an outbound network connection. Because cmstp.exe rarely makes external connections, such traffic may indicate stealthy execution or misuse of the binary. It relies on Windows network connection telemetry that includes the initiating process image path, whether the connection was initiated, and the destination IP so private and local ranges are excluded.

Reporting behind it

Related detections9 linkedT1218.003 — drag to rearrange

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Suspicious CMSTP Execution With INF Payload via process_creation

CMSTP UAC Bypass via Automatic Install Flag (via process_creation)

Windows: cmstp.exe Loading DLL/OCX from Suspicious Paths

Windows: Command-line execution of cmstp.exe with INF install/silent/autobind flags (UAC bypass pattern)

Windows CMSTP UAC Bypass Attempt via Autoelevate COM Object DllHost Execution

Windows Process Access to cmlua.dll by CMSTP Connection Manager Profile Installer

Windows CMSTP Process Spawning Child Process

Windows Registry Events: CMSTP Execution via cmmgr32.exe TargetObject

Windows Network Connection from Cmstp.EXE (Outbound)

Pivot detection · T1218.003 · 9 related

Changelog

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-network-connections-initiated-by-cmstp-exe-efafe0bf

title: Windows Network Connection from Cmstp.EXE (Outbound)
id: d21d2997-8082-4b46-8981-c69617b49523
status: test
description: This rule flags events where cmstp.exe initiates an outbound network connection. Because cmstp.exe rarely makes external connections, such traffic may indicate stealthy execution or misuse of the binary. It relies on Windows network connection telemetry that includes the initiating process image path, whether the connection was initiated, and the destination IP so private and local ranges are excluded.
references:
  - https://web.archive.org/web/20190720093911/http://www.endurant.io/cmstp/detecting-cmstp-enabled-code-execution-and-uac-bypass-with-sysmon/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/network_connection/net_connection_win_cmstp_initiated_connection.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2022-08-30
modified: 2024-05-31
tags:
  - attack.stealth
  - attack.t1218.003
logsource:
  category: network_connection
  product: windows
detection:
  selection:
    Image|endswith: \cmstp.exe
    Initiated: "true"
  filter_main_local_ranges:
    DestinationIp|cidr:
      - 127.0.0.0/8
      - 10.0.0.0/8
      - 172.16.0.0/12
      - 192.168.0.0/16
      - 169.254.0.0/16
      - ::1/128
      - fe80::/10
      - fc00::/7
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: efafe0bf-4238-479e-af8f-797bd3490d2d
    type: derived

Convert

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