t1021-005-vnc

name	T1021.005_vnc
description	Adversaries may use Valid Accounts to remotely control machines using Virtual Network Computing (VNC).
category	authorization
version	18.1
author	cyberstrike-official
tags	["mitre-attack","enterprise","t1021.005","lateral-movement","linux","windows","macos","sub-technique"]
technique_id	T1021.005
tactic	lateral-movement
all_tactics	["lateral-movement"]
platforms	["Linux","Windows","macOS"]
mitre_url	https://attack.mitre.org/techniques/T1021/005
tech_stack	["linux","windows","macos"]
cwe_ids	["CWE-284"]
chains_with	["T1021","T1021.001","T1021.002","T1021.003","T1021.004","T1021.006","T1021.007","T1021.008"]
prerequisites	["T1021"]
severity_boost	{"T1021":"Chain with T1021 for deeper attack path","T1021.001":"Chain with T1021.001 for deeper attack path","T1021.002":"Chain with T1021.002 for deeper attack path"}

T1021.005 VNC

Sub-technique of: T1021

High-Level Description

Adversaries may use Valid Accounts to remotely control machines using Virtual Network Computing (VNC). VNC is a platform-independent desktop sharing system that uses the RFB (“remote framebuffer”) protocol to enable users to remotely control another computer’s display by relaying the screen, mouse, and keyboard inputs over the network.

VNC differs from Remote Desktop Protocol as VNC is screen-sharing software rather than resource-sharing software. By default, VNC uses the system's authentication, but it can be configured to use credentials specific to VNC.

Adversaries may abuse VNC to perform malicious actions as the logged-on user such as opening documents, downloading files, and running arbitrary commands. An adversary could use VNC to remotely control and monitor a system to collect data and information to pivot to other systems within the network. Specific VNC libraries/implementations have also been susceptible to brute force attacks and memory usage exploitation.

Kill Chain Phase

• Lateral Movement (TA0008)

Platforms: Linux, Windows, macOS

What to Check

• Identify if VNC technique is applicable to target environment
• Check Linux systems for indicators of VNC
• Check Windows systems for indicators of VNC
• Check macOS systems for indicators of VNC
• Verify mitigations are bypassed or absent (4 known mitigations)
• Assess detection coverage (1 detection strategies)

How to Test

Atomic Red Team Tests

The following tests are from Atomic Red Team and provide actionable ways to test this technique:

Atomic Test 1: Enable Apple Remote Desktop Agent

ARD leverages a blend of protocols, including VNC to send the screen and control buffers and SSH for secure file transfer. Adversaries can abuse ARD to gain remote code execution and perform lateral movement.

References: https://www.mandiant.com/resources/blog/leveraging-apple-remote-desktop-for-good-and-evil

Supported Platforms: macos Elevation Required: Yes