I use this tool to flush my DNS cache and remove the DNS server addresses from my ISP network connection when I connect to my VPN. You can use this tool to do it automatically, or follow the instructions on the page to do it manually if you wish to: http://www.dnsleaktest.com/how-to-fix-a-dns-leak.php This helps to prevent DNS leaks if your VPN connection drops. One of the people that wrote it now works for the VPN I use, iVPN. That's how I found out about it. You should also use alternate, secure DNS server addresses instead of the ones your ISP provides you, like Norton DNS, or Comodo Secure DNS.