Asp.Net Interview Questions:-How
to implement security in webservice in asp.net
This is one of the most confusing ASP.NET interview question and very less developers are aware of the answer.
Webservice runs in the context of IIS and ASP.NET runtime. So you can apply all the security methodologies which you do for ASP.NET i.e. windows , passport and forms.
Click here for 32 basic .NET interview questions and answers