Dllhost.EXE Execution Anomaly — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: high. Source dates: 2022-06-27 / 2023-05-15.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 0c44a117787449492bfe698d3567cefdcfc4cee42cd5fa81df5d26dff58d613d

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: Dllhost.EXE Execution Anomaly
id: e7888eb1-13b0-4616-bd99-4bc0c2b054b9
status: test
description: Detects a "dllhost" process spawning with no commandline arguments which is very rare to happen and could indicate process injection activity or malware mimicking similar system processes.
references:
    - https://redcanary.com/blog/child-processes/
    - https://nasbench.medium.com/what-is-the-dllhost-exe-process-actually-running-ef9fe4c19c08
    - https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/goofy-guineapig/NCSC-MAR-Goofy-Guineapig.pdf
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-06-27
modified: 2023-05-15
tags:
    - attack.privilege-escalation
    - attack.stealth
    - attack.t1055
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\dllhost.exe'
        CommandLine:
            - 'dllhost.exe'
            - 'dllhost'
    filter_main_null:
        CommandLine: null
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unlikely
level: high

Original YAML and metadata in JSON

False positives

• Unlikely

Source references

• https://redcanary.com/blog/child-processes/
• https://nasbench.medium.com/what-is-the-dllhost-exe-process-actually-running-ef9fe4c19c08
• https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/goofy-guineapig/NCSC-MAR-Goofy-Guineapig.pdf