Invoke-Obfuscation Via Use Rundll32 - Security

Status: test
Severity: high
Log source: product windows, service security
Author: Nikita Nazarov, oscd.community
Source: github.com/SigmaHQ/sigma

Detects Obfuscated Powershell via use Rundll32 in Scripts

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.001` Command and Scripting Interpreter: PowerShell
Stealth	`T1027` Obfuscated Files or Information

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 4697: A service was installed in the system.

Rule body

title: Invoke-Obfuscation Via Use Rundll32 - Security
id: cd0f7229-d16f-42de-8fe3-fba365fbcb3a
related:
    - id: 641a4bfb-c017-44f7-800c-2aee0184ce9b
      type: derived
status: test
description: Detects Obfuscated Powershell via use Rundll32 in Scripts
references:
    - https://github.com/SigmaHQ/sigma/issues/1009 # (Task30)
author: Nikita Nazarov, oscd.community
date: 2020-10-09
modified: 2022-11-29
tags:
    - attack.stealth
    - attack.t1027
    - attack.execution
    - attack.t1059.001
logsource:
    product: windows
    service: security
    definition: The 'System Security Extension' audit subcategory need to be enabled to log the EID 4697
detection:
    selection:
        EventID: 4697
        ServiceFileName|contains|all:
            - '&&'
            - 'rundll32'
            - 'shell32.dll'
            - 'shellexec_rundll'
        ServiceFileName|contains:
            - value
            - invoke
            - comspec
            - iex
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    EventID: 4697
    ServiceFileName|contains|all:
        - '&&'
        - 'rundll32'
        - 'shell32.dll'
        - 'shellexec_rundll'
    ServiceFileName|contains:
        - value
        - invoke
        - comspec
        - iex

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ServiceFileName`	match	`&&` corpus 3 (sigma 3) `comspec` `iex` `invoke` corpus 2 (sigma 2) `rundll32` corpus 2 (sigma 2) `shell32.dll` corpus 2 (sigma 2) `shellexec_rundll` corpus 2 (sigma 2) `value`	`field:"ServiceFileName" kind:match`

Invoke-Obfuscation Via Use Rundll32 - Security

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`