VNC
Where this stands
One published detection covers this technique. Every one is unverified — no rule on Siemphony has been executed against real telemetry.
What the technique is
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.
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN0504
Detection of VNC service or executable starting unexpectedly, followed by user session creation and interactive desktop activity (mouse/keyboard simulation).
- AN0505
Spawning of VNC-related processes (e.g., x11vnc, vncserver) coupled with authentication logs and port listening behavior on TCP 5900.
- AN0506
Detection of VNC-based remote control via screensharingd activity in Unified Logs along with concurrent remote login activity or suspicious user interaction.
Technique names and descriptions © MITRE ATT&CK®, CC BY 4.0. Not endorsed by MITRE.