We're primarily an Ubuntu shop, but have recently configured an OpenVPN network to allow senior management to connect to our servers from their home PCs.
One of the problems we're seeing is a large increase in the number of DNS lookups coming down through the OpenVPN pipes into our DNS server for home web traffic that should be going to their ISP's DNS server and not forwarding through our private DNS server.
That traffic IS successfully stopped at the DNS server, but are there options in XP/Vista/Win7 that will allow us to restrict DNS lookup requests to certain domain names and not send those requests down the OpenVPN pipes?