i am starter for WCF. so i am looking for good write up which explain in detail what is difference in terms of security of WCF & ASMX service like how many way we can provide security for ASMX & WCF and what kind of security can be given to wcf but not possible in ASMX. if anyone know then share the knowledge with me or redirect me to right article on it. thanks
WCF provides a lot of security and binding options, but since you are interested in comparing WCF with ASMX, I am guessing you are looking at only the security options associated to web services.
WCF's security features are very much tied to the binding being used. To compare with ASMX, we should be looking at basicHttpBinding, which is designed to be interoperable with ASMX services as well. It supports almost all security features as that of an ASMX service - transport security, basic authentication, WS-Security policies.
However, to take advantage of WCF's other security features, we must take a look at WSHttpBinding, which utilizes WSHttpSecurity features that provides additional options of securing messages (and transport) by leveraging SOAP message security, that provides client authentication. Such features are not available with ASMX.
MSDN has a nice summary article on Bindings and Security which should give you a good starting point.