Windows Process Creation: svchost.exe with specific -k flags

Alerts on svchost.exe started with specific -k command-line flags consistent with suspicious persistence activity.

FreeUnreviewedSigmacriticalv1

windows-process-creation-svchost-exe-with-specific-k-flags-9f9cd389

title: "Windows Process Creation: svchost.exe with specific -k flags"
id: f12d4490-b0cb-43a4-b1a4-e129906c0387
status: test
description: This rule flags Windows process creation events where svchost.exe is started with command-line parameters matching specific -k flags. Such selective service-hosting flag usage can indicate attacker-controlled persistence or service execution rather than normal system behavior. The detection relies on process creation telemetry that records the executable path and full command line.
references:
  - https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/cold-steel/NCSC-MAR-Cold-Steel.pdf
  - https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2023/Malware/COLDSTEEL/proc_creation_win_malware_coldsteel_service_persistence.yml
author: X__Junior (Nextron Systems), Huntrule Team
date: 2023-04-30
tags:
  - attack.persistence
  - detection.emerging-threats
  - attack.stealth
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    Image|endswith: \svchost.exe
    CommandLine|endswith:
      - " -k msupdate"
      - " -k msupdate2"
      - " -k alg"
  condition: selection
falsepositives:
  - Unlikely
level: critical
license: DRL-1.1
related:
  - id: 9f9cd389-cea0-4142-bf1a-a3fd424abedd
    type: derived

What it detects

This rule flags Windows process creation events where svchost.exe is started with command-line parameters matching specific -k flags. Such selective service-hosting flag usage can indicate attacker-controlled persistence or service execution rather than normal system behavior. The detection relies on process creation telemetry that records the executable path and full command line.

Known false positives

Unlikely

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