Why not temp VM just remove it once you are done virtualbox should do fine if you want more security hire a powerfull VPS where you run your VMÅ› or a dedicated server running vmware stuff if you paying or proxmox ve if you want free still good there is ofcourse others that are free and you could run win/*nix on a server if you want to use virtualbox you can also "upgrade" and use a vpn when you connect to you server and as a free extra i give you 1 usb stick you can run any live boot cd and have usb read only anything is gone once you shutdown everything is gone or not really pull the plug for 10mins as some bits can still be in ram and used "maybe" if its sprayed quick enught (cold spray) 
