Potential Application Whitelisting Bypass via Dnx.EXE

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

Detects the execution of Dnx.EXE. The Dnx utility allows for the execution of C# code. Attackers might abuse this in order to bypass application whitelisting.

Known false positives

Legitimate use of dnx.exe by legitimate user

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1027.004` Obfuscated Files or Information: Compile After Delivery `T1218` System Binary Proxy Execution

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Potential Application Whitelisting Bypass via Dnx.EXE
id: 81ebd28b-9607-4478-bf06-974ed9d53ed7
status: test
description: |
    Detects the execution of Dnx.EXE. The Dnx utility allows for the execution of C# code.
    Attackers might abuse this in order to bypass application whitelisting.
references:
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Csi/
    - https://enigma0x3.net/2016/11/17/bypassing-application-whitelisting-by-using-dnx-exe/
author: Beyu Denis, oscd.community
date: 2019-10-26
modified: 2024-04-24
tags:
    - attack.stealth
    - attack.t1218
    - attack.t1027.004
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\dnx.exe'
    condition: selection
falsepositives:
    - Legitimate use of dnx.exe by legitimate user
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: '\dnx.exe'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\dnx.exe` corpus 2 (sigma 2)	`field:"Image" kind:ends_with value:"\dnx.exe"`