The Op needs to check his router for
Teredo tunnels, Win 8 is bad about configuring Teredo tunnels using UPnP and not closing them out. You then have open ports on your router that are not firewalled. If he has an ipv6 capable router I would suggest he sign up with a 4to6 tunnel service and turn off UPnP in his router, I would close UPnP just on general principals.
bernie