Block Register Device Notification
BlockRegisterDeviceNotification is a box-wide Boolean setting in Sandboxie Ini. When enabled, it suppresses device-notification registrations made through selected USER32 APIs. The default is n.
Runtime behavior
When the setting is enabled, Sandboxie installs user-mode hooks for:
RegisterDeviceNotificationA;RegisterDeviceNotificationW;UnregisterDeviceNotification.
The intercepted ANSI and Unicode registration calls do not invoke the underlying Windows registration function. Sandboxie clears the last-error value and returns a successful-looking placeholder handle, so the application can believe that registration succeeded even though no registration was made through that call. The intercepted unregister function likewise clears the last-error value and reports success without performing a real unregister operation.
The placeholder handle is an implementation detail and should not be relied upon by applications.
Scope and limitations
This setting suppresses registrations made through RegisterDeviceNotificationA/W; it is not a universal block on every device-change or Plug and Play notification mechanism. The current implementation does not establish that a sandboxed application can never receive WM_DEVICECHANGE, broadcast notifications, Configuration Manager notifications, service notifications, or kernel-level notifications through other paths.
In particular, the driver's separate Configuration Manager filter does not currently deny the function associated with CMP_Register_Notification. That path is distinct from the USER32 registration functions intercepted by this setting.
Applying changes
The setting can be specified for a sandbox or inherited through normal template and global configuration resolution. It has no documented executable-qualified syntax.
Sandboxie reads the effective value while initializing GUI hooks in the sandboxed process. Changing the setting does not dynamically install or remove those hooks in a process that has already initialized. Restart affected sandboxed applications, or recreate the sandboxed process tree, after changing it. A SandMan, service, or driver restart is not normally required.
SandMan configuration
SandMan does not currently provide a dedicated checkbox for BlockRegisterDeviceNotification. Configure it manually in the sandbox's INI section.
Relationship to other device features
OpenDevCMApi controls a separate driver filter for selected mutating Device Configuration Manager operations. The two settings operate independently.
USB Drive Sandboxing is SandMan host-side automation that detects qualifying USB-backed volumes and maintains forced-folder rules. BlockRegisterDeviceNotification does not control that automation and does not prevent SandMan itself from observing device changes.
Version history
Current setting metadata lists BlockRegisterDeviceNotification as introduced in Sandboxie Plus 1.9.5 / Classic 5.64.5. The corresponding runtime change made the notification-registration hooks conditional on this setting. The same release's changelog records a fix related to RegisterDeviceNotificationW registrations using DBT_DEVTYP_DEVICEINTERFACE.