The user utilized Shelter to create a separate Android Work Profile to isolate applications. The setup allowed the user to run specific apps within the isolated environment while maintaining a VPN connection in the primary profile, using split tunneling to route traffic directly for selected applications.
The author conducted six experiments using the RKNHardering diagnostic tool on a Vivo Y53s device running Android 13. The tests aimed to determine if applications within the Work Profile could detect VPN activity occurring in the primary profile despite being excluded from the tunnel.
Results showed that while applications in the Work Profile successfully routed traffic directly, they could still detect the presence of the 'tun0' network interface. The diagnostic tool identified this interface through Java API and native system records, even when the app itself was not using the VPN.
The experiments confirmed that the 'tun0' interface and associated routing information disappeared when the VPN was disabled in the primary profile. This indicates that the Work Profile does not fully hide the system-wide network state from applications, as they share the same Linux kernel and system services.
The study highlights that while Work Profiles provide data isolation, they do not guarantee complete network invisibility. Applications can still access system APIs that reveal information about network interfaces and device characteristics, which may be used to detect VPN usage.
