Remote Services: VNC
Adversaries may use Valid Accounts to remotely control machines using Virtual Network Computing (VNC). The adversary may then perform actions as the logged-on user.
VNC is a desktop sharing system that allows users to remotely control another computer’s display by relaying mouse and keyboard inputs over the network. VNC does not necessarily use standard user credentials. Instead, a VNC client and server may be configured with sets of credentials that are used only for VNC connections.
Inventory workstations for unauthorized VNC server software.
|Disable or Remove Feature or Program||
Uninstall any VNC server software where not required.
|Filter Network Traffic||
VNC defaults to TCP ports 5900 for the server, 5800 for browser access, and 5500 for a viewer in listening mode. Filtering or blocking these ports will inhibit VNC traffic utilizing default ports.
|Limit Software Installation||
Restrict software installation to user groups that require it. A VNC server must be manually installed by the user or adversary.
Use of VNC may be legitimate depending on the environment and how it’s used. Other factors, such as access patterns and activity that occurs after a remote login, may indicate suspicious or malicious behavior with VNC.