Potential Arbitrary File Download Via Cmdl32.EXE

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: frack113
Source: github.com/SigmaHQ/sigma

Detects execution of Cmdl32 with the "/vpn" and "/lan" flags. Attackers can abuse this utility in order to download arbitrary files via a configuration file. Inspect the location and the content of the file passed as an argument in order to determine if it is suspicious.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1202` Indirect Command Execution `T1218` System Binary Proxy Execution

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: Potential Arbitrary File Download Via Cmdl32.EXE
id: f37aba28-a9e6-4045-882c-d5004043b337
status: test
description: |
    Detects execution of Cmdl32 with the "/vpn" and "/lan" flags.
    Attackers can abuse this utility in order to download arbitrary files via a configuration file.
    Inspect the location and the content of the file passed as an argument in order to determine if it is suspicious.
references:
    - https://lolbas-project.github.io/lolbas/Binaries/Cmdl32/
    - https://twitter.com/SwiftOnSecurity/status/1455897435063074824
    - https://github.com/LOLBAS-Project/LOLBAS/pull/151
author: frack113
date: 2021-11-03
modified: 2024-04-22
tags:
    - attack.execution
    - attack.stealth
    - attack.t1218
    - attack.t1202
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\cmdl32.exe'
        - OriginalFileName: CMDL32.EXE
    selection_cli:
        CommandLine|contains|all:
            - '/vpn'
            - '/lan'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\cmdl32.exe'
    - OriginalFileName: CMDL32.EXE

Stage 2: `selection_cli`

selection_cli:
    CommandLine|contains|all:
        - '/vpn'
        - '/lan'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`/lan` `/vpn`	`field:"CommandLine" kind:match`
`Image`	ends_with	`\cmdl32.exe` corpus 2 (sigma 2)	`field:"Image" kind:ends_with value:"\cmdl32.exe"`
`OriginalFileName`	eq	`CMDL32.EXE`	`field:"OriginalFileName" kind:eq value:"CMDL32.EXE"`