Protecting the Host Screen During a Remote Control Session

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Blanking the host display during a remote session is essential for protecting sensitive data. It prevents onlookers from viewing the monitor or entering data while you are accessing the computer from another location. NoMachine’s remote screen blanking feature is designed to address this security need. Additionally, NoMachine offers the option to automatically lock the system screen once the remote session terminates, ensuring the desktop does not remain visible to unauthorized users.

Toggle screen blanking from the system tray

• For a quick, session-specific change, start a NoMachine session and connect to the target computer.
• Click the !M icon in the system tray of the target machine to bring up the menu (on Windows, right-click the icon).
• Select 'Desktop shared', then click 'Blank physical screen'.

Fig. 1 – Toggle screen blanking during a remote session via the system tray

Configure screen blanking in 'Server Settings'

• To make screen blanking the default behavior for all incoming connections, open the NoMachine interface on the computer you want to reach.
• Navigate to Settings, or click the !M icon in the system tray and select 'Show server status'.
• In the 'Server settings' window, select the 'Security' tab.
• Check the box for 'Blank the physical screen when somebody connects' (Fig. 2). You will be prompted for an administrator's username and password to change this setting.
• An additional option within the same Security panel lets you choose to show a 'screen shading effect when the screen is blanked'. When enabled, the blanked screen cycles from black to grey to indicate to local bystanders that a remote session is in progress. If disabled, the screen remains static black.

Fig. 2 – Enable 'Blank the physical screen when somebody connects' in Security settings

Locking keyboard and mouse input

• When screen blanking is active, NoMachine also locks the host keyboard and mouse. This prevents anyone physically present at the host machine from entering data or interrupting your work during the remote session.
• Anyone in the vicinity of the host device will see a blank screen on the physical monitor while your session is active. Once you disconnect, the screen becomes visible again. If you want the screen to remain hidden after your session ends, you should enable the automatic screen lock, 'Lock the physical screen on disconnect'.

Enable automatic screen lock upon disconnection

• You can further protect the remote computer by forcing the system's own screen lock to activate as soon as the NoMachine session ends.
• Enable the 'Lock the physical screen on disconnect' box (Fig. 3).
• Like the blanking feature, this is disabled by default and requires administrator credentials to toggle.

Fig. 3 – Configuring 'Lock the physical screen on disconnect'