WCF - IIS Integrated Security
Usually when we developing a WCF service in Intranet environment, we need to enable users to authenticate on IIS with there login credentials - Integrated Security.
Assuming we using basicHttpBinding and we host the service library on IIS web site, This can be accomplished by the following settings:
<bindings>
<basicHttpBinding>
<binding name="basicHttpBindingConfig">
<security mode="TransportCredentialOnly">
<transport clientCredentialType="Windows" />
</security>
</binding>
</basicHttpBinding>
</bindings>
Disable the "Allow Anonymous" login and enable the "Windows Authentication" login in IIS web site security settings tab.
Finally, don't forget to update the client service reference.
More about binding and security issues.