Suspicious Renamed Comsvcs DLL Loaded By Rundll32 — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: high. Source dates: 2022-08-14 / 2023-02-17.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: f1832108161c1be4480a3ea0f63c7f0db14dd47b35823a86e327239ac6e328ed

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 Renamed Comsvcs DLL Loaded By Rundll32
id: 8cde342c-ba48-4b74-b615-172c330f2e93
status: test
description: Detects rundll32 loading a renamed comsvcs.dll to dump process memory
references:
    - https://twitter.com/sbousseaden/status/1555200155351228419
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-14
modified: 2023-02-17
tags:
    - attack.credential-access
    - attack.t1003.001
logsource:
    product: windows
    category: image_load
detection:
    selection:
        Image|endswith: '\rundll32.exe'
        Hashes|contains:
            # Add more hashes for other windows versions
            - IMPHASH=eed93054cb555f3de70eaa9787f32ebb # Windows 11 21H2 x64
            - IMPHASH=5e0dbdec1fce52daae251a110b4f309d # Windows 10 1607
            - IMPHASH=eadbccbb324829acb5f2bbe87e5549a8 # Windows 10 1809
            - IMPHASH=407ca0f7b523319d758a40d7c0193699 # Windows 10 2004 x64
            - IMPHASH=281d618f4e6271e527e6386ea6f748de # Windows 10 2004 x86
    filter:
        ImageLoaded|endswith: '\comsvcs.dll'
    condition: selection and not filter
falsepositives:
    - Unlikely
level: high

Original YAML and metadata in JSON

False positives

• Unlikely

Source references

• https://twitter.com/sbousseaden/status/1555200155351228419