VPNetMon is described as 'prevents unsecured connections after your VPN connection went down. It simply closes specified applications when the VPN connection is down' and is a VPN Service in the Security & Privacy category. There are five alternatives to VPNetMon for a variety of platforms, including Windows, Android, iPad, iPhone and Linux. The best alternative is VPNCheck, which is free. Other great apps like VPNetMon are TunnelRat (Free), VPN Lifeguard (Free, Open Source), VPN Watcher (Freemium) and VPNKS (Free).
TunnelRat monitors your VPN and automatically restarts it if it stops functioning properly. If you use Microsoft's built-in VPN with the PPTP protocol you probably experience occasional problems where the VPN stops working.
To protect yourself when your VPN disconnects. It blocks Internet access and any other specified applications. It prevents unsecured connections after your VPN connection goes down and reloads applications when reconnecting the VPN.