gistfile1.js

var binding = new WSHttpBinding(
      { MessageEncoding: "Mtom"
      , SecurityMode:"TransportWithMessageCredential"
      })
   , proxy = new Proxy(binding)     

proxy.ClientCredentials.Username.Username = "yaron";
proxy.ClientCredentials.Username.Password = "1234";

proxy.send(message, function(response) {
  console.log(response)
});